Front Cover
 Preface and acknowledgments
 Table of Contents
 Dried citrus pulp
 Citrus molasses
 Citrus peel oils
 Citrus seed products
 Pulp washing for solids recove...
 Specialty food products
 Fermentation products
 Waste treatment
 Literature cited
 Back Cover

Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: By-products and specialty products of Florida citrus
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00026802/00001
 Material Information
Title: By-products and specialty products of Florida citrus
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Alternate Title: By products and specialty products of Florida citrus
Physical Description: 119 p. : ill. ; 23 cm.
Language: English
Creator: Kesterson, J. W
Braddock, R. S ( Robert James )
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1976
Copyright Date: 1976
Subject: Citrus fruit industry -- By-products -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references (p. 109-119).
Statement of Responsibility: J.W. Kesterson and R.J. Braddock.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026802
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AHM1136
oclc - 03417524
alephbibnum - 001597006

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Preface and acknowledgments
        Page i
    Table of Contents
        Page ii
        Page 1
        Page 2
    Dried citrus pulp
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
    Citrus molasses
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
    Citrus peel oils
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
    Citrus seed products
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
    Pulp washing for solids recovery
        Page 75
        Page 76
        Page 77
    Specialty food products
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
    Fermentation products
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
    Waste treatment
        Page 106
        Page 107
        Page 108
    Literature cited
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
        Page 116
        Page 117
        Page 118
        Page 119
    Back Cover
        Page 120
Full Text

BULLETIN 784 (technical)


J.W. Kesterson and R. J. Braddock

Institute of Food and Agricultural Sciences
University of Florida, Gainesville



J. W. Kesterson and R. J. Braddock
Chemist and Associate Food Scientist
Agricultural Research and Education Center
Lake Alfred, Florida, 33850

This public document was promulgated at an annual cost
of $7,615.63, or a cost of 95 cents per copy, to provide com-
prehensive information on the production and processing
of citrus by-products and specialty products.

The present bulletin was first published in 19511 and revised
by the same authors in 19652 as, "By-Products of Florida
Citrus." Information presented in this bulletin has been obtained
over a period of 30 years, a time when phenomenal growth was
made by citrus processing, by-products, and specialty product
industries in Florida.
Many advances in the technology of by-products and specialty
products have occurred within the past 10 years. All data herein
are basic and fundamental to by-product technology even though
it may not have been developed in recent years. The authors have
supplemented previous knowledge with more recent technology
in order to make this bulletin an up-to-date comprehensive source
of information for the production and processing of citrus by-
products and citrus specialty products.

This bulletin is dedicated to all segments of the Florida Citrus
Industry and especially to those commercial processors whose
earnest cooperation for the past 30 years has made this publica-
tion possible.
'Hendrickson, R., and J. W. Kesterson. 1951. Citrus by-products of Flor-
ida. Univ. Fla. Agr. Exp. Sta. Bull. 487: 1-56.
"'Hendrickson, R., and J. W. Kesterson. 1965. By-products of Florida
Citrus. Univ. Fla. Agr. Exp. Sta. Bull. 698: 1-76.

INTRODUCTION ................................................ 1
P u rpose ............................ .................... .. .......................... ........... 1
H isto r y ............................ ............ ............................................................................................................. 1
DRIED CITRUS PULP .........3...................... ............................. 3
P processing P rocedu res ............. ............................................................................ 5
P processing V ariables .... ............................ ............. .............. ............................. 11
C itru s P ellets ............... ........................ ....................... ............ ..................... 20
N u tritional V alue .......... ................. ... .............................................. 24
C IT R U S M O L A S S E S .......................... ................................................. ..................... 26
Processing Procedures ............................................. ..................... 26
Processing Considerations ........................ ................................... .......... 29
U utilization ........... ........ ............................................ .......................... ............. 37
CITRUS PEEL OILS ....... ....................................... ........... .... ........................................ 38
Methods of Commercial Manufacture ....................... ........................................ 39
C oldp ressed C itru s O ils .............................. ............................................................ 44
D e-O iler O ils ............ .. ........... ................ .............................................. 51
Distilled Citrus Oil ................... . ............... .................................... 54
E ssen ce O ils ............................................................................... ............................. 5 4
J u ic e O ils ....................................... .......................... ........................................................................... 5 6
U tiliz a tio n ................................................ ...................................... 5 8
F L A V O N O ID S .............................................................................................................................. 58
H e sp erid in ..................................... .................................... ........... .......... ....................... 5 9
N a rin g in ........................................ ......... .. ......................... ........................................ 6 1
Dihydrochalcone Sweeteners .......................................................... 63
Miscellaneous Flavonoids ................. .............. ...... .......... .................... 63
CITRUS SEED PRODUCTS ........... .................... ........... .................... .......... 64
S eed R recovery ..................................................................................... 65
Seed Oil Composition ............ .................................................. 67
Seed Meal Composition ......................................................... ....................... 69
U tiliz a tio n ........ ..... ................................... .............. ......................................... 7 1
P E C T IN .......... ........... .......................... ........ ... ................ ................. ........... 71
C o m p o sitio n .............................. .......... ......... ............................................................. 72
P processing P procedure .............................. ............ ........... ............................... 73
P ectin P om a ce ................................................................................. 74
U tiliz a tio n .... ... ..... .................. .. ............ ............................ ........................................ 7 4
PULP W ASHING FOR SOLIDS RECOVERY ....................................... 75
Processing Procedure ............................ ................ ................................................ 75
C om p o sition 7.. ........................... .......... ....... .............. ............... ....................... 76
U tiliza tion ............................... ............................. ........................... 77
SPECIALTY FOOD PRODUCTS ... ..... .............................. .......... 78
Citrus Sections and Salads ............. ............... ............................... 78
G elled C itru s P products . .... ........... .... ....... ............................ ................ 85
F rozen Ju ice S acs ............................................. .. ........................................ 87
D ried Ju ice S acs.. ............... .... ................................ ................. ............. ........ 87
C itru s P u rees ........................................................... ....................................... 92
Beverage Bases and Popsicles .......................... ...................................................... 93
Brined and Sulfited Peel ............................................................... 95
Candied Peel and Glycerated Peel ................................... ........................................ 96
M a rm a la d es ............... ...... ... ............... .......... .......................... ................................... 97
B lan d S y ru p .................................... .................................. ....................................................... 98
P eel S eason in g ..... ........ ...................... .................................................. 99
FERMENTATION PRODUCTS .... ............. ......................... ............... 101
C itru s A lcoh ol ...... ............ .. ................ .. ........................................... 101
W in e s ........................... .......................... ..................... .......... 103
M iscellan eou s P rodu cts ................. .... ......................................................... ................................ 104
W A S T E D IS P O S A L ............ ................................................................. ....................................... ...... 106
B iolog ical T reatm ent ....................................................................... 106
Effluent Limitations ............................. ........ ......................................... 108
LITERATURE CITED ........................................ .................................................................... 109


Although citrus plantings existed in Florida as early as 1579
(35) ', the spectacular growth in citrus production and processing
has occurred from 1942 to 1976. The development of frozen cit-
rus concentrates led to increasingly larger quantities of peel
residue for local disposal. The peel residue consists of the colored
outer portion of the peel called flavedo, the white inner portion
called albedo, the carpellary membranes commonly referred to
as rag, juice. sacs, and seeds. The enormous waste problem which
developed brought about the now flourishing citrus by-products
and specialty products industry.
The increasing quantity of oranges produced and processed
in Florida over the past two decades is shown in Figure 1. Grape-
fruit production and processing has remained relatively constant
over the same period. The overall result has been an increase in
citrus peel residue until approximately 8.0 billion pounds of peel,
rag, and seeds were left for disposal in the 1974-75 season. Most
of this waste residue was converted to dried citrus pulp and
citrus molasses. Production of these two important by-products
over the last 20 years is presented in Figure 2. The divergent
production trends shown are related to the economical return
from these two products (39).

This bulletin presents information pertinent to the produc-
tion, evaluation, and usage of Florida citrus by-products and
specialty products. The origin and interrelationships of the
many citrus products discussed are summarized in Figure 3. All
products depicted have been manufactured at least with pilot
plant equipment and represent more than speculation based on
laboratory trials. Besides its informative value, this bulletin
should also convince the reader of the enormous potential value
of waste citrus peel residue.

Waste peel residue became a serious disposal problem as
greater and greater quantities of citrus were processed in Flor-
"3Figures in parentheses refer to Literature Cited.




"' 100- C- 1l PRODUCED
S80 -


1953 1958 1965 1968 1973 1953 1958 1965 1968 1973
1954 1959 1966 196 1974 1954 1959 1966 1969 1974
Figure 1.-A bar graph showing the quantity of Florida oranges (90
Ib/box) and grapefruit (85 Ib/box) processed, as well as
total available, 5-year intervals (52).

ida. The residue of peel, pulp, and seeds was first dumped on
nearby pastures and fed wet to livestock. Although this was
eaten readily, it fermented and could not be stored. The citrus
industry soon learned to process the larger quantities of available
residue into a dried feed. Today, the only citrus waste dumped
in pastures is an occasional lot of cull fruit. Approximately 75
to 85% of all citrus wastes are converted into by-products. There
is also an abundance of other specialty products recovered from
citrus wastes.
Dried citrus pulp was produced in commercial quantities as
early as 1932 from citrus residues of two canneries in Tampa.
This utilization had been suggested in 1916 by F. Alex McDer-
mott (192), who had received a Mellon Institute Research Fel-
lowship to investigate the utilization of cull citrus fruits in Flor-
ida. Actual production of dried citrus pulp was accomplished in
1925 in the laboratories of the Florida Citrus Exchange. Scott
(165) of the Agricultural Experiment Station in Gainesville fed
a dried citrus product, made by Seth S. Walker in 1926, to Jersey
cows and concluded that the product had merit as a cattle feed.


The excellent qualities of dried citrus pulp were substantiated by
later investigators (10, 22, 37, 42, 116, 129) in a wide range of
feeding trials with dairy and beef cattle.
Citrus molasses is essentially concentrated press liquor ex-
pelled from waste citrus peel after adding a small amount of
lime. It was first produced commercially in Florida during the
1941-42 canning season. The limed peel residues were pressed to
remove press liquor, thereby lowering the moisture content of the
pressed peel to avoid charring that occurred in drying very wet
peel mixtures. The expelled citrus press liquor was soon recog-
nized as a potentially valuable by-product when concentrated to
molasses. This solved another difficult disposal problem. The
feeding value of citrus molasses for cattle and swine was sub-
sequently established (17, 21, 38, 41, 114).

Dried citrus pulp is usually produced in Florida between
November and June, with November and March being the slack
months. The finished product is uniform in particle size and ap-
pearance even though it is manufactured from a varying mixture

(5 Year Intervals)

= 600-


o---_- "---o--- ----- -o....
0 l -----i- I I-
1953-54 1958-59 1963-64 1968-69 1973-74

Figure 2.-A graph showing the production of dried citrus pulp and
molasses (39) at 5-year interval.

3 '








Figure 3.-Origin and interrelationships of citrus by-products and spe-
cialty products.

of orange, grapefruit, and other citrus fruit residue. As with
most feeds, citrus pulp is dried to a moisture content of approx-
imately 10% to prevent microbiological spoilage and spontaneous
The demand for a continuous year-round supply of citrus
pulp requires the product to be placed in storage, where insects
may become a problem. The almond moth, Cadra cautella


(Walker), has been shown to be present in dried citrus pulp
warehouses (63). The saw-toothed grain beetle, Oryzaephilus
surinamensis (L.), was found to be the primary species asso-
ciated with the coarse pulp, while the cigarette beetle, Lasio-
derma serricorne (F.), more commonly attacked pellets and fine
meals (118). Other insect species were also found, and suggested
control measures were as follows: 1, thoroughly clean warehouse
before moving new material into storage; 2, apply a residual in-
secticidal spray to the interior of the empty warehouse; 3, block-
stack all bagged feed; 4, make aerosol application once a week
with a pyrethrin formulation having a synergist such as piper-
onyl butoxide; and 5, the tentatively suggested use of insecticide-
coated multiwalled paper bags. More recently, warehouse control
of insects has been achieved with a wettable malathion formula-
tion. A 50 ppm residue tolerance has been approved for this
pesticide in dried citrus pulp (51).

Processing Procedures
The peel, internal membranes, ruptured juice vesicles, and
seed residue ejected by citrus fruit extractors represent the raw
material for production of dried citrus pulp. Large tonnages of
this residue are normally accumulated and held in closed storage
bins or on cement slabs. One example of open storage is shown
on the cover. The peel residue is moved by slide conveyors and
elevators to a hammer mill or shredder (Fig. 4), where high
speed rotating hammers or knives cut it into pieces approxi-
mately 1/4 by : inch. Approximately 0.2 to 0.5% lime (calcium
hydroxide or calcium oxide) is proportioned on the moving res-
idue as a powder or slurry immediately before, during, or after
shredding the peel. The lime and chopped peel are thoroughly
mixed and continually intermixed in a delayed reaction conveyor
or pug mill. More simply, this is described as a large modified
screw conveyor. Local alkalinity changes the color of the residue
to a rather bright yellow, which disappears slowly to leave a
straw-colored product as the lime reacts with the acidic com-
ponents. Experienced operators are able to judge if the proper
quantity of lime has been added by color, feel, and consistency
of the product or by its ease of pressing. The high local alkalin-
ity, occurring shortly after the lime addition, brings about a
rapid degrading and demethylation of the pectins in the peel.
Syneresis sets in, bound juices are released, the free liquid por-
tion changes to an acidic pH, and the mixture becomes more



Figure 4.-Hammer mill (courtesy Reitz Manufacturing Co., Santa Rosa,


fluid and much less slimy. Processors using a pug mill allow a
minimum of 5 to 10 minutes for the lime to react. When vertical
storage bins are used, approximately 30 minutes of curing time
is necessary before pressing. Continuous mixing encourages
rapid curing. This also eliminates the agglomeration of the
chopped peel into unmanageable chunks. The cured citrus residue
may be dried with or without pressing.
When limed citrus residue is pressed in the continuous
presses, the moisture content is reduced ordinarily from 80 to
84% to approximately 70 to 72%. The pressed residue and press
liquor are then processed independently as diagrammed in the
flow and material balances shown in Figures 5 and 6. The cured
and pressed residue is conveyed to rotating driers, and is dried
to 8 to 10% moisture. After being dried, the citrus pulp, the hot
combustion gases and moisture pass into a cyclone separator.
The dried solids fall onto the wall of the cone, while the hot
gases and moisture exhaust either to a waste heat evaporator
or to the atmosphere. From the separator, the dried pulp passes

(85,000 Ibs.)
479% JUICE 52.14%
40,700 Ibs. of JUICE EXTRACTOR 44,300 Ibs. of PEEL, PULP ( SEEDS
(app. 1393 CasesNo2 Cans) 81.9% MOISTURE
(8020 Ibs. Dry Matter)
Recovered from 40,700 Ibs. SHRED, 95 Ibs. of COLDPRESSED
53.6% 46.4%
23,800 lbs. of PRESS CAKE CURE, 20,500 Ibs. of PRESS JUICE
5705 Ibs.of DRY MATTER PRESS 2315 lbs. of DRY MATTER

EVAPORATE 17,595 bs. of 95 Ibs. of EVAPORATE 17,800 Ibs. of
6205 Ibs. of DRIED CITRUS PULP 321 Gallons
5705 Ibs of DRY MATTER 2315 lbs. of DRY MATTER

Figure 5.-Flow and material balance sheet for the processing of
Duncan grapefruit residues into dried pulp and molasses.


(90,000 Ibs.)
556% JUICE 444%
50,000 Ibr.of JUICE ET R 40,000 Ibss of PEEL,PULP ( SEEDS
(app.1766 Cases No2 Cans) 82% MOISTURE
I ( (7200 Ibs. Dry Motter)
Recovered from 50PO00 bs. SHRED, 256 bs.of COLOPRESSED
44 (0.2-0.5%) 55.6%
44.4%1 55.6% ,
17,760 Ibs. of PRESS CAKE CURE, 22,240 Ibs. of PRESS JUICE
4973 Ibs.of DRY MATTER I -- 2224 lbs. of DRY MATTER

EVAPORATE 12,335 Ibs.of 256 Ibs. of EVAPORATE 18,892 Ibs. of
4973 Ibs. of DRY MATTER 2224 Ibs.of DRY MATTER

Figure 6.-Flow and material balance sheet for the processing of Va-
lencia orange residues into dried pulp and molasses.

to a cooler that is usually a rotating drum with countercurrent
air flow. The dried pulp is divided into three products at this
point. The countercurrent cooling air carries off the fines or dust,
which is collected in a cyclone separator; a rotary screen on the
lower end of the cooling drum separates the portion called citrus
meal; and the material carried through is the dried citrus pulp.
A typical plant normally produces 85% dried citrus pulp, 14%
citrus meal, and 1% fines. The meal has passed through a screen
of approximately 14 mesh4, although this varies from plant to
plant. An overall view of an experimental feed mill for producing
dried citrus pulp is shown in Figure 7.
Many processors make a so-called sweetened pulp, adding 20
to 50% citrus molasses (made from the expressed press liquor)
to the curing peel residue. Sometimes more than 50% molasses is
added, depending on the marketing area, but care must be exer-
cised since molasses addition darkens the color of the pulp. The
actual quantity of molasses added to citrus pulp can be deter-
mined by Bissett's procedure (24). A comparison of the com-
position of dried citrus pulp, meal, sweetened pulp, and other
citrus products is shown in Table 1. The average mineral com-

4All mesh sizes refer to U.S. Bureau of Standards sieve numbers.


position of dried citrus pulp is shown in Table 2. Some of the
more commonly requested physical constants for various citrus
products are presented in Table 3. The addition of molasses to
citrus pulp increases the soluble carbohydrate content while de-
creasing the fat, fiber, and protein content. Crude fat content
of citrus pulp is greater when the dried pulp is made from one of
the more seedy citrus varieties. Dried citrus pulp is slightly
hygroscopic, and if proper care is not taken, the product will
increase in moisture content during storage. Moisture contents
of greater than 12 to 14, in dried citrus pulp can result in mold
formation, lowering of feed quality, and generation of sufficient
heat to cause spontaneous combustion.
Dried citrus meal has slightly higher fiber, nitrogen-free ex-
tract and ash contents than citrus pulp, but is lower in fat con-
tent, according to Kirk and Davis (115). The meal was found

Figure 7.-Experimental feed mill at the Agricultural Research and Ed-
ucation Center, Lake Alfred.


Table 1.-Composition of citrus feed products
Dry Crude Crude Free Crude
Citrus Product Reference Matter Protein Fiber Extract Fat Ash

Whole Fruit Percent Percent Percent Percent Percent Percent
Grapefruit, cull 116 13.64 1.07 1.39 10.03 0.64 0.51
Oranges, grated 116 14.84 0.96 1.58 11.34 0.32 0.64
Tangerines 116 17.39 1.01 1.38 13.62 0.80 0.58

Undried Peel Residue
Citrus peel 20 18.49 1.23 2.22 12.48 1.83 0.73
Citrus peel, pressed 20 28.27 2.01 4.36 17.80 2.65 1.45
S Grapefruit peel, pressed 116 25.23 2.24 4.61 15.74 1.18 1.46
Dried Citrus Residue
Citrus pulp
(71 analyses) 128 90.1 5.9 11.5 62.7 3.1 6.9
Citrus pulp
(10 anal. 64-65 prod.) 92.0 6.2 12.0 64.0 4.9 4.9
Citrus pulp, sweetened
Grapefruit pulp 128 92.0 5.3 9.3 66.6 2.8 8.0
(3 seasons) 10 100 6.4 12.1 56.9 5.5 -
Grapefruit pulp
(5 lots) 148 100 7.0 15.3 5.9 6.5

Dried Meal
Citrus meal 116 88.27 6.47 12.39 60.55 2.94 5.93

Table 2. Average mineral composition of dried citrus pulp (2).
Macro No.
Minerals Samples Average Range Std. Dev.
%-Calcium 82 1.43 0.76 2.13 0.27
%-Magnesium 82 0.121 0.104- 0.141 0.008
%-Phosphorus 82 0.111 0.086- 0.194 0.017
%-Potassium 82 1.09 0.78 1.32 0.10
%-Sodium 82 0.096 0.051- 0.272 0.043
%-Sulfur 10 0.066 0.024- 0.152 0.037
ppm-Iron 35 98.72 31.33 -214.36 41.81
ppm-Copper 35 6.19 3.23 17.58 2.87
ppm-Zinc 35 9.94 6.04 13.34 2.24
ppm-Manganese 35 5.70 4.48 6.62 0.57
ppm-Cobalt 10 0.073 0.036- 0.105 0.021

Table 3.-Physical constants for various citrus products.
Bulk Density Specific Specific
Product Ib/cu ft Heat Gravity

Meal 27-30 0.43-0.48
Pulp 17-24 0.388 0.27-0.38
Pellets 42-46 0.67-0.74
Juice sacs 8-10 -0.13-0.16

Peel 52-55 0.83-0.88

by Becker and Arnold (19) to weigh 0.97 pound per quart, while
citrus pulp weighed from 0.57 to 0.80 pound per quart. Com-
mercial practice has established 25 pounds per cubic foot as a
reasonable average density for dried citrus pulp. When placed
in storage, 120 cubic feet per ton of dried pulp are allowed for
stacked bags and aisles.
Costs of processing, warehousing, and selling dried citrus
pulp and molasses have been analyzed by Sherrod, Ward, and
Spurlock (167).

Processing Variables
Pressing Operation

Plants that operate continuously find it desirable to press the
eel and produce both dried citrus pulp and molasses. Consider-
le savings can be effected by the use of multistage evapora-


tors, even though greater capital expenditures are necessary.
The water is more efficiently evaporated in such equipment.
Citrus molasses, however, is generally not as economical an out-
let as citrus pulp. Plants that operate intermittently often find
it more economical to dry the unpressed peel, since overhead and
labor costs are considerably lower. An alternative to pressing has
been used in Texas (166). The limed peel was placed temporarily
in 10-ton curing bins that allowed the liquor to drain away after
release. Drying cured citrus peel residue without pressing is
complicated by a tendency of the residue to stick and burn in
the drier. This problem is alleviated by recycling a portion of
dried or semidried peel to give a moisture content of 70 to 72%
entering the drier. This requires about 25% of the discharge
from the second stage of the drier (30% moisture) or about 17%
of previously dried feed (8% moisture). Sometimes such re-
cycling is necessary only when the drier is initially started.
Various types of continuous presses are used in the Florida
citrus industry. More commonly found are the Davenport press,
the Louisville continuous press, the Vincent continuous press,
and the Zenith pulp press.
In the Davenport press, cured citrus residue is conveyed to
the top opening of an intake hopper and dropped between two
large revolving perforated disks. The disk faces are progressively
closer as they approach the discharge port. The increasing pres-
sure expels the press liquor through the minute openings of the
perforated disks, after which it drains from the bottom of the
press. The fibrous character of the peel acts as a filtering
medium, aiding the screen plates in preventing the fine solids
from passing off with the liquid. The compressed peel is removed
continuously by a discharge bar that forces it out the exit after
a 3/1 revolution.
The Louisville continuous press is composed of a sectional,
endless belt of perforated hinged plates which pass continuously
over a series of supporting rolls. Each perforated metal section
offers a pressing surface. The section passes between a series of
paired rollers, one a supporting roller, the other a pressure roller.
As the cured pulp is fed to the press, it forms a fibrous mat that
retains the fine solids. The series of paired rollers provides an
almost continuous wringing action, forcing the press liquor
through the perforated filtering plates and discharging the com-
pressed pulp at the far end.
The Vincent continuous dewatering press is horizontal, re-
volves at a low speed, and is of similar, but heavier construction



than a conventional juice finisher. The cylindrical screw spindle
is surrounded by reinforced 0.020 inch screens. Cured citrus
residue is fed into the intake opening, and a perforated hydraulic
cone applies back pressure to the exit end of the press. Press
liquor is forced through both the screen and the cone, and drains
from the bottom of the press into a collection trough. The pressed
peel is removed continuously to a conveyor system that feeds the
pressed peel to the drier.
The Zenith continuous pulp press is essentially a vertical
screw press. It consists of a heavy, tapered, screw-type spindle
surrounded by a series of downward deflectors. This spindle is
perforated on the lower half and revolves at a relatively low
speed inside a reinforced cylindrical screen of stainless steel. The
cured peel enters the press at the top and during its downward
movement is constantly rolled over and continuously forced by
screw deflectors through a restricted, tapered opening. Vanes
projecting through the outer screen act to retard and turn over
the pulp while it is compressed. Press liquor is forced through
the small perforations of the outer cylindrical screen, as well as
through those of the tapered spindle. At the bottom, the pulp is
still under pressure and is forced through a second restricted,
tapered opening to remove more press liquor. Figure 8 illustrates
this last type of press.

Drying Operation
Three types of driers are found in this industry: the direct-
fired rotary, steam-tube rotary, and a triple pass parallel heat
flow rotary. These three types of driers are shown schematically
in Figure 9.
The direct-fired rotary is composed of a long cylindrical shell,
usually 8 feet in diameter and 60 feet long. It is fired by oil. The
hot combustion gases pass directly over the wet pulp, moving
in the same direction as the pulp.
The steam-tube rotary drier has a shell similar to the direct-
fired rotary, but the wet pulp and air are heated by steam tubes
within the shell of the drier. The hot air flows countercurrent to
the pulp. Baffles, attached to the rotating shell, move the pulp
slowly through the drier. These driers are adapted to multiple-
stage drying.
The third type drier, a triple pass parallel heat flow rotary,
uses hot combustion gases from a direct-fired furnace for drying.


Figure 8.-Zenith pulp press. (Courtesy Jackson and Church Company,
Saginaw, Michigan.)


i n Air Flow




Pulp (- -- --

Figure 9.-A schematic diagram of three types of driers for citrus

through the drier. The hot water-laden gases flow in the same
direction as the pulp and discharge into a cyclone separator for
Among the many disadvantages attributed by Heid (67) to
o-fired rotary driers are excessive kiln temperatures, burning


of fines, lower yield, and fire hazard from bagging burning
particles. These can be eliminated by multiple-stage drying or by
lowering the temperature in the drier.
When a comparison was made by Pulley and von Loesecke
(148) of dried grapefruit pulp manufactured by three types of
driers, they found no significant difference between the products
except where pressing was avoided. None of the samples con-
tained carotene after drying. Braddock and Kesterson (26, 30)
demonstrated that the monohydroxy- and dihydroxy-carotenoid
fractions of orange and tangerine flavedo were easily destroyed
during drying in a pilot plant feed mill. Greater losses of pig-
ments occurred by increasing feed mill dryer temperatures.
Samples dried at exit-stack gas temperatures of 210 and 230F
were light in color and showed the least loss of pigment during
drying. Extensive destruction of pigment occurred in other sam-
ples dried at an exit gas temperature of 290F. Since 290F is
widely used in commercial feed mills, a re-evaluation of citrus
pulp drying temperatures was suggested. Addition of an antioxi-
dant to the flavedo prior to drying aided in reducing pigment
destruction during the drying operation. When Pineapple orange
and Dancy tangerine flavedo were carefully dried at 225F util-
izing an antioxidant (200 ppm BHA), 306 and 568 mg of total
carotenoids per kilogram were found respectively. Exit-stack gas
temperatures of 290F resulted in caramelization of a portion of
the invert sugars, degraded protein and gave a much darker
feed. Ammerman et al. (4) and Chapman et al. (37) have shown
that a dried citrus pulp dark in color is less palatable and has
less nutritional value due to a reduced digestibility of protein
and lower energy value.
Moisture content of peel residue is an important variable
that can profoundly influence the drying process. It need not,
however, have any effect upon the quality of the manufactured
dried pulp. Grapefruit peel, for example, will have a higher
moisture content than orange peel. Similarly, truck-transported
peel usually will have a higher moisture content than directly
extracted residue. During recovery of oil, the moisture content
of the peel residue may be increased. In the FMC-In-Line ex-
tractor, when mist spray cups are used to produce oil, approxi-
mately 9 to 12 pounds of water are absorbed by the peel from
each 90-pound box of oranges. Residue from a citrus section
production line has considerably greater moisture content than
citrus residue from any other source. Moisture content is
lated to the conversion ratio of wet peel residue to dried cit s


pulp (8 to 10% moisture). At one time, a 10 to 1 conversion
ratio was considered a typical industry average, while today it
is probably about 4.5-5.5 to 1. Under the best conditions, how-
ever, it could be as low as 3.8 to 1. Peel residue of high moisture
content not only decreases production capacity and increases fuel
cost for drying, but also encourages sticking in the drier. The
latter condition causes burning in the drier and a greater pro-
portion of charred particles in the dried pulp. If high moisture
content is a persistent condition, it is almost imperative that
continuous presses be used.
Peel residues will also vary in physical appearance when
different juice extractors are used. The residue may be recovered
from either the FMC-In-Line extractor shown in Figure 10 or
from a Brown extractor (Fig. 11). Each type of residue has dis-
tinct by-product possibilities. Peel from an FMC extractor has
more cells broken, which aids in drying, but it probably will
yield more fines. The FMC extractor mashes and shreds the peel,
which causes it to become watery and translucent after a few
hours holding time. This phenomenon is related to the stage of
fruit maturity, holding time, and temperature. Undoubtedly,
natural enzymes are released when the peel is mashed. These en-
zymes degrade and demethylate the pectin, resulting in a peel
that is not as firm as fresh peel. Peel from the Brown extractor
remains firm for a much longer period of time. Each of these
extractors can be adapted to segregate the residue into an inner
fruit portion and an outer fruit portion. However, when the
Brown extractor is coupled with the Brown shaver, it has the
further capability of separating the whole reamed half peels
into shaved albedo and shaved flavedo. An arrangement of this
type makes it possible to segregate citrus refuse into more dis-
tinct component parts thereby facilitating the recovery of by-
products and specialty products.

Bulk Storage
Within the past 10 years, bulk storage (Fig. 12) of dried
citrus pulp has become a common practice for most of the
Florida citrus processors. Dried citrus pulp consists of a great
number of particle sizes and large variations occur in the phys-
ical properties with maturity, variety, type of processing equip-
ment, etc. They vary from a very fine dust to peel segments %
inch in length. Dried citrus pulp is a non-free-flowing material
tat tends to bridge over outlet orifices; flow can only be re-
stred by mechanically breaking the bridge. Consequently, much


q !L

Figure 10.-The FMC-ln-Line juice extractor with oil recovery acceis-
sories. (Courtesy FMC Corporation, Lakeland.)


Figure 11.-Peel residue leaving a Brown reamer. (Courtesy Brown
International Corp., Covina, Calif.)

Products, Inc., Bradenton, Fla.)


engineering technology and experimentation has gone into the
development of a system to handle this commodity. In most bulk
storage warehouses, the dried peel is moved and handled by air
conveyors. During transport, the peel is classified and sorted into
various particle sizes as it is delivered and deposited in the stor-
age area. When the warehouse is unloaded, the various pulp sizes
must be recombined in the same proportion that they were de-
livered to the warehouse in order to restore homogeneity to the
Bulk storage plants are massive warehouse areas either of
masonry or steel construction ranging from 300 to 400 feet in
width, 400 to 600 feet in length, and 40 to 60 feet in height.
These warehouses can store from 6,000 to 8,000 tons of dried
citrus puln. The interior of the warehouse is divided into dis-
tinct bins or sections into which the pulp is placed. A highly
sophisticated system of thermocouples is installed so that the
temperature of the pulp can be monitored continuously in any
section of the warehouse. Air vents are installed in the floor
through which air can be forced to regulate the temperature in
the event of localized overheating. Cleanout ports are installed
in the outer walls of each section so that the pulp can be removed
in case of a fire. Fire or smoldering is a distinct danger in feed
mill operations and usually occurs when the moisture content
of the dried feed is in excess of the recommended 10% moisture
level as discussed under processing procedures.
Many advantages occur from bulk storage, namely: 1, re-
duced storage costs; 2, reduced handling costs; 3, reduced trans-
portation costs; and 4, elimination of bag cost of approximately
$10 per ton. These economic advantages are passed on to the

Citrus Pellets
Dried citrus pulp is a bulky carbohydrate concentrate. Its
low bulk density coupled with poor handling characteristics re-
sults in high storage and handling costs when compared to other
feed materials handled in bulk storage bins (196). In other feeds,
these problems have been overcome by pelleting. Citrus pellets
have been produced in Florida on a limited scale since the middle
1950's. At that time, the meal and dust (12 to 15% of the total
weight) were converted into 1/4 inch pellets which were added
hack to the dried pulp in the exact same proportion that they
occurred in the feed. This resulted in a higher density feed which


could be more easily consumed by dairy animals, the major out-
let for this commodity. Within the past 5 years, approximately
25% of the total dried citrus pulp produced in Florida has been
pelletized for export. It is contemplated that in the future, prac-
tically all of the dried citrus pulp will be converted into pellets.

General Procedure
There are two basic types of pelleting processes. One is the
continuous extrusion process, and the other is the closed cylinder
process in which only one pellet is formed at a time. There are
three basic types of machines used for the extrusion process.
They are the reciprocating piston type, the roller type and the
screw type. The first two extruders are characterized by high
pressures and relatively low capacities, while the screw extruder
is characterized by low pressures and high capacities.

Pelleting Process
In the Florida citrus industry, whole dried pulp with a mois-
ture content of 10 to 12% is conveyed directly from the feed mill
cyclone separator by screw conveyors to the pellet machine. The
hot dried peel bypasses the feed mill cooling reels in order to
conserve the heat in the dried product. Normal feed mill practice
dictates a moisture content of 8 to 10% in the final dried prod-
uct. However, when whole dried peel is pelleted it is not neces-
sary to lower the moisture content below 10 to 12% since friction
in the pellet mill will reduce the moisture content to an accept-
able level. Drying to a final moisture content of 10 to 12% in-
creases the capacity of the drier and makes for a more efficient
feed mill operation from an energy utilization standpoint.
Florida processors generally use either the Sprout-Waldron
or California Pellet Mill (Fig. 13) to pelletize citrus pulp. Both
types of equipment are continuous roll type extruders. Each
manufacturer produces equipment of varying capacity, pellet
size, pellet shape, horsepower requirement, etc., to suit the needs
of an individual processor. Pellet machines are capable of pro-
ducing 10 to 25 tons per hour. Pellets are then conveyed to a
cooler where they are cooled and dried as the processing pro-
cedure dictates. The cooled pellets are then conveyed to silos or
storage tanks for distribution by bulk delivery trucks or other
means of conveyance.

Pellet Size
Pellet mills are capable of producing pellets from 1/4 to 1 inch
diameter by changing the dies. However, 1/4 inch pellets have


Figure 13.-California Pellet Mill. (Courtesy California Pellet Mill Co.,
San Francisco, Calif.).

become regarded as a standard for citrus meal and dust. Larger
sized pellets produced from fines have a lower mechanical dur-
ability than the 1/ inch pellets. Whole dried citrus pulp is nor-
mally pelleted into % inch pellets in order to retain pulp fibers
and seeds, factors which make a more acceptable feed. The 1/
inch pellets are normally 1 to 1-1/ inch in length while the %
inch pellets vary from 1/ to :%1, inch in length. The thickness of
the die, holding time, and diameter of pellet are variables that
have a direct bearing on the properties of the pellet as well as
the amount of energy required to produce the pellet. Extrusion
rate and bulk density (196) have been shown to be inversely
proportional to die length while extrusion energy was directly
proportional to die thickness.

Varietal Effect
Dean (44) has shown that pellets made from grapefruit wer
slightly less durable than those made from early and midseas


oranges. The grapefruit pellets were lighter in color and lower
in density. Pellets made from Temple oranges were much less
durable than pellets made from the other orange varieties.

Bulk Density
Pelleting dried whole citrus pulp (17 to 24 lb/cu ft) in-
creases the density to 45 to 46 pounds /cubic feet, or a twofold
increase in bulk density. In comparison to bulk pulp, more than
twice as many tons of pellets can be placed in the same storage
area. Fewer deliveries are needed, and transportation costs are
lowered for both the citrus processor and the consumer. Pelleted
pulp is a cleaner product than unpelleted pulp since it is free of
dust. Pelleting also reduces the chance of fire in the storage area.
Pellet size also influences the bulk density; the smaller the di-
ameter the greater the density.

Handling and Conveying
Pellets are conveyed by three different types of conveyors,
as follows: 1, screw conveyors; 2, belts; and 3, bucket elevators.
It has been found in commercial practice that less damage and
disintegration of pellets occurs when the pellets are conveyed
laterally with belts and raised vertically with bucket elevators.
Screws tend to break up the pellets.

Microbiological Stability
Dean (44) found that pelleted citrus pulp had superior re-
sistance to microbiological deterioration when compared to com-
mercial citrus pulp, even when the pellets contained twice as
much moisture. However, high moisture content causes the pellet
to crumble; so in order to produce a durable pellet the moisture
content should not, in general, exceed that of dried citrus pulp.
It appears that pelleting citrus pulp would substantially improve
its present storage qualities, especially under Florida conditions.

Bonding Agents
The adhesive forces inside pellets depend upon the high pres-
sures employed. Bonding agents increase the natural adhesion
and thereby reduce the pressure required to form pellets. Both
blackstrap and citrus molasses are suitable bonding agents for
citrus pulp. Citrus molasses would appear to be the more prob-
able choice for commercial applications because of its availability
to citrus processors. The nutritive value of citrus molasses will


also contribute substantially to the high-energy nutritional con-
tent of citrus pellets. The level of molasses addition, in the range
of 5 to 15% of the total weight, has been found to be a satisfac-
tory level which does not affect the physical durability of the
pellet. Current processing technology does not use bonding agents
for pelleting citrus, since 350 Brix molasses from the waste heat
evaporators is added back to the wet pulp in the pug mill prior
to pressing and drying.

Storage of Pellets
Citrus pellets are stored and handled in the following man-
ner: 1, silos; 2, farm storage tanks; and 3, bulk storage areas.
Concrete silos (Fig. 14) are similar to grain elevators and have
a storage capacity of 800 to 1,300 tons of pellets per unit. Indi-
vidual silos range from 20 to 120 feet in height and have a di-
ameter of 25 to 26 feet. Silo clusters consist of 12 to 15 individual
units with a total storage capacity of 10,000 to 20,000 tons. Farm
storage tanks are normally constructed of corrugated metal and
are typical of those used for storing grain. Bulk storage areas
are the same as those used for the bulk storage of dried citrus
pulp (Fig. 12). These facilities are of the most modern design
and many are computer controlled. Connecting conveyors from
the silos, bulk tanks, or bulk storage areas are used to load pellets
into tank trucks, freight cars, or ocean-going cargo ships.

Nutritional Value
Dried citrus pulp is second only to corn as a source of con-
centrated feed nutrients for Florida dairy and beef cattle, and
sheep (115). It is a good source of calcium, but low in phospho-
rous and carotene (19). Several investigators have compared
citrus pulp with ground snapped corn and found no significant
differences in animal gain, efficiency of feed utilization, and im-
provement in grade (4, 5, 19, 37, 38, 129, 141). Ammerman (3)
has shown that steers when fed 66% regular pulp gained 2.61
pounds per day and those fed 66% pelleted pulp gained 3.04
pounds. This suggested difference in gain may have resulted
from the greater feed consumption by steers fed pelleted pulp.
Based on these data, dried or pelleted citrus pulp is one of the
most desirable energy feeds and can be considered in feeding
programs as being: 1. a dry carbohydrate concentrate with high :
total digestible nutrient (TDN) content averaging about 74%,
2. a bulk energy feed with a high degree of water absorptiorq,


Figure 14.-Silos for the handling and storage of citrus pellets.
(Courtesy Cargill Inc., Commodity Marketing Division,
Tampa, Florida.)

and 3. having an above-average palatability for cattle. As a gen-
eral rule, 40 to 45%, of the ground snapped corn in a dairy ration
can be replaced by dried citrus pulp or pellets. Pounden (145)
has demonstrated that 15 pounds of dried citrus pulp or 50
grams of hesperidin complex fed daily to dairy cows for 5 months
reduced the incidence of mastitis caused by Streptococcus aga-
Hinton (84) has studied the relative xanthophyll utilization
of orange and tangerine flavedo when incorporated into poultry
diets. The pigment in orange and tangerine flavedo was not
utilized efficiently to pigment broiler shanks but showed a 30.1%
utilization for egg yolk pigmentation.



Tapa Florda.

and3.hain a avearag paaaiiyfrcate sagn


Molasses is made from citrus by curing waste residue with
small quantities of lime, after which continuous presses expel a
press liquor or juice that is concentrated to a syrup. Approxi-
mately 0.20 to 0.50% calcium hydroxide is required to react with
the chopped citrus residue to facilitate the release of bound
juices. The expelled press liquor contains 9 to 15% soluble
solids, of which from 60 to 75% are sugars. This liquor has a
biological oxygen demand of between 40,000 and 100,000 ppm
(124) and can create a waste disposal problem if pumped into
the ground or dumped into lakes or streams. By concentrating
this straw-colored, bitter liquid in multiple-effect evaporators, a
viscous dark brown molasses is obtained that is readily accepted
when fed to cattle. The final product, as now manufactured in
Florida, is required to meet the following minimum state stand-
ards: it must contain 45% total sugars expressed as invert sugar
and test not less than 35.50 Brix by dilution with an equal weight
of water (54).

Processing Procedures
Conventional Evaporators
The conversion of the released citrus press liquor to citrus
molasses begins usually by passing it over a vibrating screen
(40 to 80 mesh) to eliminate the larger particles. The screened
liquor is held temporarily in a storage tank until it can be pas-
teurized through heat exchangers that flash the liquid under
pressure from 240F to atmospheric conditions. This operation
serves four purposes: peel oil is distilled off and recovered as an
additional by-product, the high temperature kills all spoilage
organisms, calcium citrete and other calcium salts with inverted
solubility are precipitated, and flocculation and sedimentation of
other suspended matter are aided. Multiple-effect evaporators,
schematically shown in Figure 15, are used in concentrating the
hot liquor to 500 Brix whereupon it is usually screened (40 mesh)
to eliminate the larger scale particles that may have loosened in
the evaporator. A forced circulation finishing pan completes the
concentration to 720 Brix.

Waste Heat Evaporator Techniques
The conventional method for processing plant residues has/
been to dry the peel in direct fired dryers which exhaust the


so G.P.M.
A 150F
I n i3 F.C.
221' 173' 115, 145'
5 600 Lb.. C B

o 0 0

Figure 15.-Flow and material balance for a four-body triple-effect
vapors and particulate emissions directly to the atmosphere. The
press liquor from the peel is concentrated to molasses using
steam in multiple-effect evaporators with a finishing pan.
Waste heat evaporators have been developed within the past
10 years by the Florida Citrus Industry in order to conserve
energy and at the same time reduce the amount of particulate
emissions discharged to the atmosphere from feed mills. In order
to secure condensation of the vapors at a useful temperature
level, the fuel must be burned with little excess air. To reduce the
gas volume (which improves dryer efficiency), a recirculation of
exhaust gases and vapors is necessary. Of particular note is the
fact that when methane gas is burned as a source of energy,
2-1/1 pounds of water vapor is formed per pound of gas burned.
In a waste heat evaporator system, the water vapor from the
wet peel and combustion of the fuel in the dryer is delivered to
the vacuum tube system through either a flash evaporator or
"scrubber to remove the particulate matter. These vapors are con-
densed and the usable energy recovered. When a boiler is used
as a source of energy, the water vapor from the combustion of
the fuel is exhausted to the atmosphere and lost.
Several systems have been devised to utilize waste heat for
processing citrus residues. Two different approaches have been
developed: 1, Vincent/Lund system; and 2, Gulf Machinery sys-
The Vincent/Lund Process supplies heat partly from a fur-
naee and partly from the feed mill exhaust. A flow diagram for

to~~~I seuecnesto o h aosa ueu eprtr

the 27umtb ytm hog ihrafls vprtr
!cubrt eoetepriuat atr hs aosaecn

I 3 3 2




Figure 16.-Flow sheet for Vincent/Lund waste heat and juice evap-
orator system.


the Vincent/Lund waste heat and juice evaporator system is
shown in Figure 16. This unit can operate independently as an
evaporator without the feed mill dryer. The exhaust gases from
the feed mill and vapors from the furnace are utilized through
a flash evaporator to concentrate the press liquor to 35 to 400
Brix molasses which is recycled to the freshly chopped peel
through the Vincent diffusion system (double pressing). This
system raises the soluble solids content of the press liquor from
10 to 120 Brix to about 18 to 200 Brix, thereby lowering the
energy required to concentrate the press liquor to 35 to 400 Brix
molasses. As a consequence, the solids content of the press cake
going to the dryer is increased, which in turn reduces fuel re-
quirements and gives a greater feed output from the dryer. The
flash evaporator has the further advantage of removing dust,
soot, etc., from the feed mill emissions.
The vapors from the flash unit provide heat for the evapora-
tion of juice in a multiple-effect evaporator to produce a 65 to
700 Brix concentrate at a temperature not to exceed 145F, with-
out the use of boiler steam. The concentrate is of excellent qual-
ity and low viscosity. In this system, it is necessary to pasteurize
and stabilize the fresh juice prior to concentration. Economizers
are used to cool the concentrate and lower the energy required
for pasteurization.
The Gulf Machinery Process for utilizing waste heat from
feed mill driers is somewhat different from that of the Vincent/
Lund system. Waste heat is used solely to concentrate waste
effluents and press liquor from the citrus processing plants. A
boiler is required to supply steam to concentrate the juice in a
TASTE (thermally accelerated short time) evaporator. Flow
and material balance data for this system were not available.

Processing Considerations
Composition and Degrees Brix of Press Liquor
Table 4 shows maximum, minimum, and seasonal average
analyses of press liquor from one processing plant (134). The
extent to which the press liquors (Table 4) have been diluted by
less concentrated effluents in normal plant operation can be es-
timated by comparing the Brix values in this table with those
\ of laboratory prepared press liquor from different citrus varie-
fies as shown in Table 5. The Brix of the press liquor expressed
fB om oranges is higher than that from grapefruit, while in each
cultivar the Brix of the peel juice can be expected to be approxi-


Table 4.-Approximate composition of press liquor from a citrus processing
plant (134).
Constituent Maximum Minimum Average

pH 6.4 5.4 5.7
Brix at 17.5C 12.6 6.1 10.1
Total solids, % 11.61 5.64 8.93
Volatile matter, % 94.36 88.39 91.07
Sucrose, % 3.09 1.20 2.40
Reducing sugars, % 5.81 2.82 4.23
Total sugars, % 8.58 4.08 6.63
Protein (N x 6.25), % 0.59 0.40 0.47
Pectin (alcohol ppt.), % 0.88 0.27 0.66
Pentosans, % 0.42 0.23 0.31
Ash, % 0.94 0.43 0.72
Fixed acid, as citric, % 0.30 0.15 0.21
Volatile acid, as acetic, % 0.78 0.01 0.14
Alcohol, % by vol 0.39 0.00 0.22
Peel oil, % by vol 0.58 0.12 0.23

Table 5.-Comparison of fruit juice Brix and press liquor Brix of the same
No. of Fruit Juice Press Liquor
Cultivar Samples Average Brix Average Brix

Hamlin 9 11.2 12.3
Pineapple 3 13.0 14.3
Valencia 8 11.9 13.8
Marsh 5 9.2 11.0
Duncan 4 10.7 13.3

mately 15% higher (1 to 20 Brix) than the corresponding fruit
juice. This liquor is straw-colored and turbid in appearance and
has a pH ranging from 5.0 to 7.0. The press liquor will include, at
times, quantities of a more dilute peel-oil recovery effluent that
would be difficult to dispose of by customary sanitation proce-

Composition of Citrus Molasses

A typical analysis of Florida citrus molasses compiled from
published data (69, 95, 126) is shown in Table 6. In this table/
the ash constituents are shown in considerable detail. A con-


prison between citrus molasses and blackstrap molasses is found
in Table 7. Blackstrap molasses has a much higher ash content
and lower protein content, and has been more highly concentrated
than citrus molasses. Standards for citrus molasses have been
established at a lower level of concentration to avoid a viscosity
problem that is aggravated by the increased quantity of insoluble
suspended material formed during manufacture. Table 8 shows
the composition of citrus molasses carefully prepared in the
laboratory by clarification and filtration. The orange samples had

Table 6.-Typical analysis of Florida citrus molasses.
Brix 72.0 Potassium (K) % 1.1
Sucrose % 20.5 Calcium (Ca) % 0.8
Reducing sugars % 23.5 Sodium (Na) % 0.3
Total sugars % 45.0 Magnesium (Mg) % 0.1
Moisture % 29.0 Iron (Fe) % 0.04
Protein (N x 6.25) % 4.1 Phosphorus (P) % 0.06
Nitrogen-free extract % 62.0 Manganese (Mn) % 0.002
Fat % 0.2 Copper (Cu) % 0.003
Fibre % 0.0 Silica (SiO.) % 0.04
Ash % 4.7 Sulphur (S) % 0.17
Glucosides % 3.0 Boron (B) % 0.0006
Pentosans % 1.6 Niacin (ppm) 35
Pectin % 1.0 Riboflavin (ppm) 11
Volatile acids % 0.04 Pantothenic acid (ppm) 10
pH 5.0 Viscosity 25C (centipoises) 2000

Table 7.-Comparative data on citrus and blackstrap molasses.
Citrus Molasses Blackstrap (55)
Analysis Commercial* Laboratory* Louisiana Cuban
Brix 72.0 73.1 90.7 87.2
Sucrose % 19.6 26.1 30.1 37.3
Reducing sugars % 22.9 24.9 26.4 16.6
Total sugars % 43.5 52.4 58.0 55.8
Ash, carbonate % 4.7 3.0 10.8 10.9
SProtein (N x 6.25) % 4.1 3.6 1.6 2.1
"\pH 5.0 5.9 5.7 5.5
\Average of 36 samples
"'Average of 16 samples

\ a

Table 8.-Citrus molasses prepared from peel of different citrus cultivars.
Total oBrix Viscosity
Type of Invert Sugar (refrac- Ash 30C Apparent"
Citrus Sugar As Invert tometer) Content Centi- Purity
Peel % % 28C % poises %

Marsh 14.6 44.5 70.3 4.09 186 63.3
Marsh 17.0 48.9 76.5 3.43 880 63.9
Marsh 17.6 51.3 78.4 4.39 1660 65.4
Marsh 16.6 46.8 73.0 3.26 265 64.1
Avg. 16.4 47.9 72.5 3.79 748 64.2
Duncan 22.7 51.4 70.7 2.72 180 72,7
Duncan 22.9 50.6 71.9 2.38 194 70.4
Duncan 25.2 56.1 77.7 2.76 905 72.2
Avg. 23.6 52.7 73.4 2.62 430 71.8
Pineapple 30.9 52.0 69.7 3.03 129 74.6
Pineapple 32.0 51.2 69.8 2.60 150 73.3
Pineapple 33.7 53.9 73.6 3.03 420 73.2
Avg. 32.2 52.4 71.0 2.89 233 73.7
Hamlin 25.7 55.5 74.2 2.89 510 74.7
Hamlin 27.3 54.3 73.9 2.91 820 73.5
Hamlin 29.3 55.9 73.9 2.40 75.6
Hamlin 31.0 57.3 73.3 2.36 360 78.2
Avg. 28.3 55.7 73.8 2.64 563 75.4
Valencia 32.0 55.8 72.9 2.52 295 76.5
Valencia 19.4 52.7 70.2 3.11 345 75.1
Avg. 25.7 54.2 71.5 2.81 320 75.8

"Apparent purity refers to proportional percentages of soluble solids found to
be sugars by chemical analysis.

a greater proportion of sugars present than the grapefruit sam-
ples. Ash content and viscosity were greatly reduced by clarifi-
cation and seemed essential to the general processing techniques.
However, this technique was never adopted by industry. Annual
production of citrus molasses at 5-year intervals is compared in
Figure 2, which shows production to have remained relatively
static for the past 20 years. Molasses can be blended with
pressed citrus peel prior to drying, which is often more profitable.
Waste heat evaporators produce a 35 to 400 Brix molasses
that is added to the limed and chopped peel in the pug mill prior
to pressing. When this system reaches equilibrium, the press
liquor is about 200 Brix as compared to the 10 to 120 Brix press
liquor from fresh peel. The net result of this equilibrium is more
through-put of raw material in the drier and evaporator, making/
more efficient use of the energy necessary to manufacture driedL
citrus pulp. The 35 to 400 Brix molasses is not a stable product


and cannot be held for long periods in storage tanks. Scale is
not a problem in waste heat evaporators since the soluble solids
do not exceed 40%. Unpublished data show the oil content of
waste heat molasses to range from 0.240 to 0.278% while high
density molasses (720 Brix) ranged from 0.001 to 0.002%.

Clarification of Press Liquor
The various procedures used for the clarification of press
liquor have been: filtration, screening, centrifugation, flotation,
and sedimentation. Clarification is best accomplished by flash
pasteurization, which hastens the settling of the insolubles in
press liquor by eliminating peel oil buoying action. When press
liquor is clarified and concentrated to molasses, a much darker
product is obtained. The darker color of this improved product
is sufficient to prejudice some into believing the product has been
burned or overcooked, whereas it appears dark only because of
fewer suspended particles to reflect the incident light.

d-Limonene Recovery
d-limonene, or citrus stripper oil, as it is commonly called, is
obtained as a by-product from the manufacture of citrus molas-
ses. The names apply to the peel oil that has been subjected to a
lime treatment in the feed mill and recovered by distillation
from citrus press liquor. Press liquor which contains from 0.20
to 0.50% of this peel oil is normally passed through preheaters
(240 to 250F) for pasteurization and scale removal and flashed
to atmospheric conditions (212F) to recover the oil. The con-
densate contains approximately 60 to 80% of the oil present.
When flash pasteurization is not used, the oil recovered from the
second, third, and fourth effects of the molasses evaporator is
called condenser oil. This oil is much darker in color than stripper
oil (water white) due to the prolonged exposure to heat. The
condensate is put into a closed florentine-type tank which per-
mits the d-limonene to float to the top of the tank where it is
continuously decanted into drums or storage tanks. Since press
liquor is usually made from a mixture of citrus fruit, recovered
stripper oil represents similarly a mixture of steam-distilled
citrus oils. It frequently possesses a fine citrus oil character,

tains very little of the waxy material ordinarily present in ex-
ressed citrus oils. Tables 9 and 10 give the physical and chemical
operties of this oil.


Table 9.-Physical and chemical properties of d-limonene (25 samples of
citrus stripper oil).
Stripper Oil Maximum Minimum
Specific gravity 25C/25C 0.8433 0.8398
Refractive index D 1.4721 1.4713

Optical rotation a 25 +98.90 +95.55
Aldehyde content, % 1.50 0.47
Ester content, % 2.46 0.07
Evaporation residue, % 0.79 0.03

Factors important for the prevention of autoxidation of
water-free d-limonene during storage have been described by
Newhall and Kesterson (131). It is suggested that 50 to 100 ppm
of butylated hydroxytoluene be added and air scrupulously ex-
cluded by purging with nitrogen or carbon dioxide.
Since stripper oil is over 95% d-limonene, it is considered one
of the purest sources for this mono-cyclic terpene. A synthetic
spearmint oil flavor, 1-carvone, as well as many other synthetic
odor materials are manufactured from this oil. Considerable
quantities of d-limonene are bought yearly by the plastics indus-
try and converted into synthetic resins, adhesives, etc. This oil
is also used as a solvent, as a base for soap and perfume, in the
manufacture of rubber, as a penetrating oil, and in many other
chemical applications. Newhall has described procedures for con-
verting limonene into diacetate, dipropionate, and dibutyrate
esters (133), and into several new aminoalcohols (132) and
stereospecific cis- and trans-epoxides (130). Patrick and New-
hall (140) have shown further that the aminoalcohols have
useful fungicidal activity.

Viscosity of Citrus Molasses
Citrus molasses undergoes changes in storage that leads to
increased viscosity (78). A gelatinous structure is slowly formed
which results in a viscosity increase that can be broken by stir-
ring or heating. In most cases, the la7 increases in viscosity
that occur during prolonged storage can be eliminated almost
entirely by vigorous agitation. Further static storage, however,
brings about new viscosity increases at correspondingly similar
rates. A viscosity increase of more than 500 centipoises per da


Table 10.-Chemical constants for d-limonene.

d-limonene 1,8(9) p-menthadiene
Purity 94 to 98%
Color colorless
Odor clean citrus odor
Hanus iodine No. 79.1
Copper strip No. 0

Optical rotation a 25 +96 to +104'

Refractive index 20 1.4710 to 1.4740

Specific gravity 250 C/250 C 0.838 to 0.843
Acid No. 0.40
Aldehyde, % 0.37 to 1.50
Ester, % 0.07 to 2.46
Evaporation residue, % 0.03 to 0.80
Peroxide value not more than 2.0
Saponification No. 1.50
Kauri Butanol No. 62.75
Viscosity at 250 C 3.5 centipoises
Flash point 121 F closed cup
Freezing point -96.90 C
Sp. heat (cals/g mol) = 59.62 at 20.2 C
Temp. Coef. of Entropy (ds/dT) p 0.2032 at 20.20 C
Coef. of Expansion ml/gal (C) 2.88
(F) 1.61
ml/drum (C) 158.2
(F) 88.3

can be expected to cause trouble, since without agitation, the
molasses will exceed its initial viscosity by 45,000 centipoises
and probably solidify within 3 months. This increase in viscosity
can be reduced by passing the molasses through a heat exchanger
to temporarily redissolve the crystals. The quantities of pectin,
pH value, and total sugars are not significantly related to initial
viscosity or to the rate of viscosity increase while in storage;
however, insoluble solids and possibly small differences in grade
of pectin present are factors of greater importance. Occasion-
ally, there is a gradual crystallization of the citrus glucosides
(naringin or hesperidin) during storage.


Scale Formation in Citrus Molasses
A major problem in the manufacture of citrus molasses is
the large quantity of scale formed on the heat transfer surfaces
in the concentrating equipment. Analyses have shown this scale
to be predominantly calcium citrate. The condition is encouraged
by the lime added for curing the citrus residues. The industry
has met the problem with different approaches. Most processors
have found it advantageous to encourage scaling in the press
liquor preheaters, which are more readily cleaned than evapo-
rators. Others go further and use a parallel arrangement of pre-
heaters that permit alternate cleaning without a shutdown. Kil-
burn (112) was able to substitute waste lye from the sectionizing
plant for part of the lime addition. This decreased scaling and
eliminated a portion of the load on the waste disposal system.
Substitution of magnesium for a portion of the calcium, by using
a calcined dolomitic limestone in place of high purity dehydrated
lime for curing peel residue, offers another possible alternative
toward decreasing scale. The preheaters and citrus molasses
evaporators are cleaned of scale with a 5 to 15% boiling solution
of caustic or a mixture of caustic and soda ash in combination
with a 2 or 3% solution of a chelating agent such as alkaline
ethylene diaminetetraacetic acid that is circulated over the heat
exchange surfaces.

Foaming in Citrus Molasses
Spontaneous foaming (69) has been a problem in all types
of molasses, and although it happens only infrequently with
citrus molasses, it can represent a major economic loss. The exact
cause of foaming is unknown; however, a reduction of viscosity
and suspended solids greatly reduces the likelihood of it happen-
ing. Its occurrence is decreased also by avoiding the mixing of
old and new molasses, by avoiding alkaline processing conditions,
and by storing only cooled molasses. Avoidance of conditions en-
couraging microbial activity also is suggested.
Once the foaming or frothing has begun, there are a few
procedures that have been found helpful without any one being
a consistent remedy. Some form of agitation i Salways needed.
Following is a summary of the corrective measures to control
1. Mechanical
a. Compressed air injection
b. Recirculation pumps


c. Stirring
d. Reprocess
2. Chemical Anti-Foam Agents
3. Temperature Control
a. Compressed air (cool)
b. Recirculation pumps (cool)
c. Live steam (heat)
4. Bacteriological
a. Recirculation or mixing
b. Sulfur dioxide
c. Pasteurization

Storage of Citrus Molasses
In storage, citrus molasses decreases in pH as during the con-
centrating period. Processing press liquor to molasses reduces
the pH by approximately one unit, while storage throughout
one season would decrease pH by another 0.4 unit (79). The
latter decrease is variable and is dependent on storage time and
original pH. The lower pH increases the corrosive action of citrus
molasses on storage tanks and other iron equipment.

Feeding Value
Citrus molasses is an excellent animal feed. As such, it was
estimated by Becker et al. (21) to contain 1.4% of digestible
crude protein and 56.7% of total digestible nutrients. The bitter-
ness imparted by naringin to citrus molasses was not a detriment
in feeding dairy cows. Grasses were effectively ensiled with 2 and
4% citrus molasses. Citrus molasses was used by Baker (17) to
replace one-half of the ground snapped corn in a steer fattening
ration without reducing gains, grade, or yield. In a similar appli-
cation, Kirk and Davis (115) found citrus molasses to be palat-
able for all classes of beef cattle and to be one of the cheapest
energy feeds available in central Florida. The comparative feed-
ing value of citrus molasses and blackstrap molasses was shown
to be about equal, with citrus molasses being more palatable in
steer feeding trials by Chapman et al. (38) and Kirk et al. (114).
This became a slight disadvantage when steers ate too greedily
at the expense of efficient utilization.


Citrus molasses can be fed to swine. Cunha and co-workers
(41) found that molasses could be used to replace corn in the
feeding ration at the 10, 20, and 40% level depending on the age
of the pigs. It took 3 to 7 days for the animals to become accus-
tomed to the taste of citrus molasses.

Other Uses
One of the major uses for citrus molasses in recent years has
been its fermentation to ethyl alcohol, which in turn is sold as
brandy neutral spirits by two commercial Florida firms. Yeast
production with Torulopsis utilis, a fast growing yeast, was first
evaluated in dilute citrus molasses by Nolte et al. (134). Later,
Veldhuis and Gordon (188) adapted the fermentation into a
continuous process. Yeast contains usually about 50% protein
and could be a valuable feed supplement provided production
costs were more favorable. Somewhat similarly, lactic acid has
been manufactured on pilot plant scale, but its manufacture has
since been discontinued. It is also a source for the recovery of
citrus bioflavonoids. Still other means of utilizing citrus molasses
include the production of bland syrup (69), citrus vinegar (123),
2,3-butylene glycol (120), riboflavin and citric acid (57), meth-
ane (125), and other products.

The peel oil, or essential oil as it is sometimes called, is the
first product recovered from citrus cannery residue. Each of the
Citrus species-orange, grapefruit, tangerine, tangelo, murcott,
lemon, and lime-has an oil that commands a price which justi-
fies its recovery.
Citrus oils are confined in oblate to spherical-shaped oil
glands that are located irregularly in the outer mesocarp or
flavedo of the fruit. These glands or intercellular cavities have
no walls of the usual type and are imbedded at different depths -
in the flavedo of all citrus fruits. The cells surrounding the oil
glands contain colloids and an aqueous solution of sugars and
salts, which exert pressure on the glands. Winton and Winton
(199) and Braverman (33) more thoroughly described the exact
location of these oil sacs in the structure of the flavedo of the
Methods of oil extraction used in Florida were investigated
by Kesterson, Hendrickson, and Braddock (106, 108, 109, 101),


and results of studies relative to the physical and chemical prop-
erties of Florida citrus oils were presented.

Methods of Commercial Manufacture
General Processing Procedure
Citrus peel oils have been expressed in Florida by seven dif-
ferent types of equipment: 1, Pipkin roll; 2, screw press; 3,
Fraser-Brace excoriator; 4, FMC rotary juice extractor; 5, FMC-
In-Line Extractor; 6, AMC scarifier; and 7, Brown peel shaver.
In past years, the FMC-In-Line Extractor has been used to pro-
duce approximately 60% of the oil produced in Florida, and the
remaining 40% has been made with the screw press. During the
past 4 or 5 years, the Brown peel shaver has replaced most of the
screw press installations.
In the extraction of citrus oil, there exists a misconception
that the oil is pressed from the peel or fruit. Actually, the oil
cells are ruptured by pressure or abrasion, and the oil is washed
away. It is most important that an excess of water be maintained
to prevent the oil from being reabsorbed by the albedo, pulp, etc.,
once it is released from the fruit or peel.
The general processing procedure used after the extraction
of oil from the peel is similar in most of the commercial plants.
The crude oil emulsion is put through a screw or paddle type
finisher with a screen opening of 0.020 to 0.027 inch or passed
over a 20 to 80 mesh shaker screen. This operation recovers
substantially all of the oil emulsion present in the slurry. Exces-
sive finisher pressures should be avoided so as not to incorporate
excessive quantities of pectin and insoluble solids which increase
the viscosity and make the emulsion harder to break in centri-
fuging. The finished emulsion should contain 1 to 3% oil and no
more than 2 to 4% bottom solids, preferably less.
The finished emulsion is fed to a desludger centrifuge (8,000
to 10,000 rpm) to produce an oil-rich emulsion. The oil-rich emul-
sion should contain 70 to 80% or higher oil content. The aqueous
discharge effluent should not contain more than 0.1 to 0.25% oil
under optimum operating conditions, and the sludge effluent
should be no higher in oil content than the feed emulsion and
should usually be considerably less.
The oil-rich emulsion is fed directly to a self-thinking type
polisher centrifuge (16,000 to 18,000 rpm) without water ad-
dition. The feed rate to the polisher should not exceed 1 to 1.5
gallons per minute depending upon the capacity of the polisher


and the oil concentration in the feed. The aqueous discharge from
a self-thinking type polisher should contain no more than 5 to
7% oil. If the polisher does not have the self-thinking feature,
water should be added to the polisher feed at a rate of from 3 to
20 parts to 1 part of oil-rich emulsion from the desludger. This
water is not needed to break the emulsion, but is used primarily
to keep the polisher clean. In large installations, two polishers
should be used to minimize losses.
Following separation, the oil is usually blended and de-waxed
in stainless steel tanks. Preferably, they should be as tall as
practical and narrow in diameter. The bottom should be conical
with a drain valve at the bottom. A side drain should be located
several inches above the top of the cone to provide ample room
for the wax to settle to the bottom of the tank. This makes it
possible to decant the clear oil directly into 55-gallon shipping
drums. These tanks should be maintained in rooms at a tempera-
ture ranging from -10 to +25F, since de-waxing is a function
of time vs. temperature. For orange oil, 5 days at -10F is suffi-
cient to de-wax the oil, while it may require up to 3 weeks at
+25F. Oils that contain greater quantities of wax will require
longer holding times. These tanks should have a capacity prefer-
ably of 1,000 to 5,000 gallons to provide blending of a sufficiently
large amount of oil to result in uniformity of quality and color.
They should be equipped with covers. Tailings in the settling
tank can either be filtered or centrifuged to remove the wax.
Drums (18 gauge) for storage and shipping should have the
interior treated with one or two coats of a phenolic resin-based
enamel, especially formulated for terpenes. Apparently one coat
is adequate, since this is a one-time shipping drum. These 55-
gallon drums should be filled to contain 400 pounds of oil. This
not only results in lower drum costs, but gives a minimum of
head space and therefore much less air. Air is usually excluded
from the containers to prevent deterioration due to oxidation.
Exclusion of air usually is accomplished by displacement of the
air with nitrogen or carbon dioxide. The ideal storage tempera-
ture is 65 to 70F. At this temperature, no further precipitation of
wax will occur, and the oil will remain clear.
The plant laboratory should maintain technical control of the
operation by making routine analyses of the oil content several
times a day at the following points: oil emulsion from the fin-
isher, desludger feed, aqueous and sludge effluents and oil-rich
emulsions from the desludger, polisher feed, and aqueous and
sludge effluents from the polisher. Flow rate and oil content data


will permit accurate evaluation of the operation of the oil system,
detect areas of oil losses, and result in maximum efficiency.
All pumps should be of the positive displacement type, slow
speed, and corrosion resistant. Fittings and lines should be of
stainless steel.

Pipkin Roll Method of Extraction
In this method, the oil is expressed by passing peel of the
fruit between two striated rollers of stainless steel that turn in
opposite directions. The distance between the two rollers is ad-
justed so that the pressure against the peel is just sufficient to
puncture the oil cells without breaking or rasping the peel. Small
striations or grooves are distributed over the entire surface of
the rolls. They are of a depth sufficient to receive the oil from
the oil cells and keep it out of contact with the peel, thus re-
ducing it absorption by the albedo of the fruit.

Screw Press Method of Extraction
In this method, tapered screws press the peel against a per-
forated screen, thereby squeezing out the oil. The operation can
be carried out with the screws in either a vertical or horizontal
position. Water may or may not be used in the pressing operation.
The yield of oil is directly proportional to the surface area of the
peel coming into contact with the screen. Consequently, five 2-ton
presses will give a greater yield of oil than one 10-ton press.

Fraser-Brace Excoriator
Whole fruits are passed through a corridor of carborundum
rolls in this process. As the fruit passes through the excoriator,
it is repeatedly turned over, and abrasive rolls rasp the flavedo
from the fruit. Water sprays directed onto the fruit and rolls
wash away the oil and grated peel. The oil-water emulsion and
peel raspings are passed over a screen to remove the suspended
solid particles. The machine is completely enclosed, and very little
loss of oil is encountered.

FMC Rotary Juice Extractor
The FMC Corporation rotary juice extractor provides a meth-
od whereby both the juice and the peel oil emulsion from whole
fruit are obtained simultaneously, but in such a manner that
they do not come in contact with each other to any great extent.
This machine is of the rotary type and has 24 squeezing heads
which are all actuated by a common cam. Whole fruit is fed into


a squeezing cup where just enough pressure is applied to remove
all juice from the fruit and at the same time rupture the oil cells.
The juice and the oil emulsion are collected in separate trough
assemblies. This machine has mostly been replaced by a more
efficient counterpart called the FMC-In-Line Extractor.

FMC-ln-Line Extractor
The FMC-In-Line Extractor (108) was so named because the
series of extraction cups are situated in a straight line. This unit
is used for all citrus cultivars. The upper cups are mounted on a
common crossbar which, by means of a cam-drive, is moved in
a fixed up and down path. The corresponding lower cups are held
in rigid position. The sides of these cups consist of numerous
fingers that intermesh when the upper and lower cups are
brought together. A circular cutter tube is fastened in the bottom
of each of the lower cup members, and this protrudes below into
a strainer tube. Mounted below the lower cups and enclosing the
strainer tubes is a manifold which is common to all of the lower
cups and strainer tubes of a single machine. An unperforated
orifice tube closely fitted inside the strainer tube slides up and
down inside the cutter.
The fruit is delivered by a conveyor belt to the rear side of
the machine, where there is a joined series of runways, one for
each cup. A cam-driven lift functions as a positive means of
placing fruit individually into the lower cups. The motion of lift
is synchronized with the movement of the upper cups and also
with the orifice tubes mounted on the lower bar.
When the fruit is placed in the lower cup, the upper cup is
moved down in a smooth stroke, pressing the fruit against the
cutter tube. This cuts a plug in the fruit. As the upper cup con-
tinues its downward stroke, the entire inner portion of the fruit
is forced down into the strainer tube within the manifold. At the
same time, the orifice tube moves upward inside the strainer
tube, causing the juice to be forced through the perforated
strainer tube into the manifold. The stroke is completed when the
upper cup completely meets the cutter tube, thus sealing off this
tube and cutting a plug in the upper portion of the fruit. At this
point of the stroke, the inner portion of the orange which has
been forced into the strainer tube is completely pressed of juice.
At the same time, the peel of the fruit is shredded and dropped
into a screw conveyor trough which carries it to the by-product


When an oil cup assembly is used to recover the peel oil ex-
pressed during the juice extraction operation, the upper and
lower cups are reversed. Cup-shaped baffles surround the fingers
of the upper cup, and as the oil is released by the shredding ac-
tion, it is collected on the baffles and directed to one side of the
extractor. Considerable volatilization of the oil accompanies this
operation, as evidenced by the aroma of the surrounding atmos-
phere. The oil and aqueous matter expressed from the outer peel,
along with small particles of outer peel, are mixed with a small
amount of water to provide fluidity. This mixture is put through
a finisher equipped with a fine screen to remove insoluble solids
and gives an oil emulsion from which peel oil is separated later.
An improvement for increasing the yield of oil may or may
not be added to the above machine. At the same instant the oil
is released from the peel, a fine mist of water is sprayed which
prevents volatilization of the oil. It has been reported that oil
yields may be increased by 50% with addition of sprays. The
"mist spray" nozzles deliver from 3 to 6 gallons of water per
minute per extractor. Approximately 9 to 12 pounds of water
is absorbed by the peel from each 90-pound box of oranges.

AMC Scarifier
The American Machinery Corporation method of releasing
oil from the peel of citrus fruits is essentially a refinement of the
"Avena," "Speciale," and other rasping methods used in Italy
and other Mediterranean countries. This scarifier is designed for
continuous operation, and it is placed in the conveyor line to the
juice extractors.
The scarifier resembles the universally used transverse brush
washer in its design and manner of handling the fruit. It consists
of a frame in which cylinders made of stainless steel sheets that
have been pierced with a square punch are mounted at right
angles to the flow of the fruit. The punch has pierced the stain-
less steel in such manner as to cause sharp points of the metal
to stand up similar to the points in a nutmeg grater. It is these
points that puncture the oil cells of the citrus peel. These cylin-
ders, usually about 22 in number, rotate on a stainless steel shaft.
A variable speed drive controls the speed of rotation to permit
adjustment to fruit of varying size and characteristics. The
stainless steel cylinders are actually formed of four pieces of
metal fastened to a shaft by means of a casting to which they
have been screwed. Each piece forms approximately 1/4 of the


cylinder. They are so arranged that they are self-cleaning of the
The frame in which these rolls are mounted is inclined upward
at a rather steep angle. This permits the fruit to pile up deeply
at the intake end and assures additional piercing action by the
weight on the bottom fruit that is in contact with the perforated
The entire interior of the enclosure contains a mist of water
provided by fog-type spray nozzles. This water washes the re-
leased oil from the surface of the fruit, saturates the flavedo with
moisture, and thus restricts the reabsorption of the oil by the
fruit. A moisture-saturated atmosphere in the area above the
fruit discourages escape of the oil through openings in the en-
closure. At the discharge end of the machine, the spray nozzles
provide heavier streams of water to wash the fruit and brushes.
The oil-laden water from the scarifier is captured as an emul-
sion in a stainless steel pan beneath the machine.
Brown Peel Shaver
The Brown peel shaver is a unique means for extracting the
oil from citrus peel. Peel cups or quarters from juice extractors
are fed into this machine, wherein, a wide knife blade splits the
peel into flat slices of albedo and flavedo. The albedo slice, being
on top, is conducted to the outside. The flavedo slice, being on the
other side of this divider, is completely separate; and while under
complete control and flat, it is given a knurled roll pressing in
the presence of water to release and transfer its oil to the water.
Separation of the oil/water mixture from the flavedo is then
made with a Brown paddle finisher.
An easy adjustment on the machine allows any thickness of
the slice, from paper-thin flavedo to the removal of rag only,
with or without pressing. The shaver is also used for preparing
products and by-products from citrus peel, including dragged
peel, intact flavedo and albedo, pectin, color, flavonoids, marma-
lade strips, fillers, and candied or pickled products.

Coldpressed Citrus Oils
Relation of Yield to Properties and U.S.P. Specifications
The U.S.P. specifications (180) for orange oil require a spe-
cific gravity between 0.842 and 0.846 (25C/25C), a refractive in-
dex between 1.4720 and 1.4740 (20C), an evaporation residue
greater than 43 mg/3 ml oil and an optical rotation of +940 to
+ 990 (25C). The 10% distillate of the oil should have a refrac-


tive index 0.0010 to 0.0020 units less than the original oil and an
optical rotation equal to or not more than +20 greater than
original oil.
The factor found to influence the physical and chemical prop-
erties of coldpressed oil of orange to the greatest extent is the
yield of oil secured from the peel. Higher oil yields lead to in-
creased values of the specific gravity, evaporation residue, and
refractive index, but decrease the values for optical rotation. As
the yield of oils increased, more high-boiling, high molecular-
weight constituents are evidently extracted. The presence of a
higher percentage of these compounds in the oil causes a reduc-
tion in the percentage of d-limonene. This leads to lower optical
rotation values, since d-limonene is the most optically active com-
ponent in the oil.
Yields of oil obtained by the various methods of processing
fluctuate from 1.85 pounds per ton of peel to 9.70 pounds per ton
of peel. Commercial plants often have more peel than it is pos-
sible for them to process for maximum amount of oil recoverable
from the peel. This being the case, the plants are operated to
produce the maximum amount of oil on an hourly basis. To do
this, they partially extract the oil from a large quantity of peel
rather than secure the maximum recovery of oil from a smaller
quantity of peel. Hence, they may secure very low yields of oil
despite their capability of obtaining much higher yields with the
same equipment.
Any processor can produce an oil meeting U.S.P. specifica-
tions using available equipment, provided he is willing to operate
it in a manner that will secure the necessary yield of oil. On the
basis of the data accumulated, it is estimated that a yield of 3.0
to 7.5 pounds of oil per ton of fruit from 'Pineapple' oranges or
the extraction of 25 to 60% of the total amount of oil in the peel
of any orange variety of good maturity will result in a cold-
pressed oil that will meet the specifications as given in the United
States Pharmacopoeia (180).

Effects of Aqueous Phase on Aldehyde Content
Although the flavor and aroma of an oil of orange is depend-
ent upon all of its many constituents, the aldehyde content is
recognized as having special importance and is included in the
U.S.P. specifications (1.2 to 2.5%).
In one plant where other variable factors were kept constant
while the water used in the process was reduced from extremely
large quantities to an equivalent of 100 gallons of aqueous phase


per gallon of oil produced, the aldehyde content increased from
1.08 to 1.64%, a 52% increase. Accordingly, it was evident that
to produce an orange oil of high aldehyde content, the amount
of aqueous phase in contact with the oil during processing should
be reduced as much as is practical under operating conditions.
Recent work has shown that as the quantity of aqueous phase
is increased, the amount of insoluble solids increases. These in-
soluble solids, primarily pulp particles, presumably act to absorb
constituents from the oil. Loss of aldehydes in an oil recovery
plant using large quantities of water, therefore, may be as readily
explained by absorption loss as by solubility loss.

Relation of Fruit Variety to Properties
The physical properties of expressed orange oils obtained
from different varieties of fruit are not significantly different.
There are processing differences, of course, but even these re-
main constant throughout the season.
"The aldehyde content of coldpressed oils of orange is highest
when made from 'Valencia' oranges. Mixtures of 'Pineapple' and
seedling oranges yield oils with lower aldehyde contents, while
mixtures of 'Hamlin' and 'Parson Brown' varieties give oils of
the lowest aldehyde content.
Variety of fruit apparently has very little influence on the
ester content of the orange oils. Oils of orange produced by the
Fraser-Brace excoriator are higher in esters and evaporation
residues than oils manufactured by any of the other methods.
Oils from mid-season varieties that are partially green in color
are considerably higher in ester content than those made by the
same process later when the fruit is completely orange in color.

Storage of Fruit Prior to Oil Extraction
The length of time fruit is stored prior to the extraction of
the oil is another factor which influences the characteristics and
quality. The physical properties of coldpressed oils of orange ex-
tracted from fruit on the same day of harvest are not signifi-
cantly different from those oils extracted from fruit stored for
3 to 5 days before being extracted. Kesterson et al. (101) found
significant differences in the chemical properties of oils from
these fruit. The ester content of the oil from stored fruit was
31.3% higher than that from fruit which had not been stored.
The evaporation residue of the oil from the stored fruit was
9.6% higher, and the aldehyde content was 4.6% lower.


Effect of Maturity on Properties
Here again, differences were noted in the chemical character-
istics rather than in the physical properties.
The aldehyde content of 'Valencia' orange oils increased as
maturity increased, reached a maximum when extracted during
the early part of the Valencia season from fruit that just passed
the maturity standards, and then decreased after peak maturity
had been reached. The ester content of these oils was lowest when
extracted during the early part of the Valencia season and grad-
ually increased as the fruit became more mature. 'Valencia'
oranges that had passed peak maturity produced an oil with the
highest ester content of any oils secured during the year.

Effect of Yearly Variations on Physical Properties
A comparison of the 1947-48 fruit season, which was consid-
ered to be a very wet year, and the 1948-49 fruit season, which
was considered to be a very dry year, was expected to show dif-
ferences in the physical characteristics of the oil. Only one factor,
however, was affected to any extent. The values for refractive
index averaged 0.0008 of a unit higher during the dry 1948-49
fruit season.

Physicochemical Procedure to Determine Origin
and Method of Extraction
The physicochemical properties of coldpressed orange oils
have revealed differences in the ultraviolet spectra and in the
evaporation residues that reflect the geographical source of an
oil and the method by which it was extracted. Kesterson et al.
(107) have shown that these two values could be used as a basis
to identify and characterize coldpressed orange oils as shown in
Table 11. The CD value is an optical density reading that meas-
ures the amplitude of a UV peak. It is determined at 330 mrt for
orange oil by diluting 0.25 g to 100 ml with 95% ethanol and
reading in a 10 mm cell.

Aldehyde Content vs. Rainfall
The aldehyde content of expressed orange oil will vary con-
siderably from one season to another. Low aldehyde content oils
are generally considered to be inferior to oils with a high alde-
hyde content from the standpoint of flavor and aroma. For this
reason, it would be desirable to always produce an oil with a


Table 11.-Evaporation residue and CD values for orange oils.
Type Oil CD Evaporation Residue

California 0.10 to 0.20 not significant
Screw press 0.20 to 0.40 below 2%
FMC-ln-Line 0.20 to 0.40 above 2%
Pipkin roll 0.40 to 0.60 not significant

high aldehyde content. However, this has not been possible since
the factors responsible for this phenomenon have not been fully
understood. Data collected for 14 years show how the aldehyde
content of 'Valencia' orange oil is influenced by rainfall and how
this information can be used to forecast or predict what the alde-
hyde content will be for any given season (101).
The aldehyde content of 'Valencia' orange oil showed a posi-
tive correlation with the total rainfall with a correlation coeffi-
cient of 0.603 which is significant at the 5% level. The aldehyde
content of the oil rose with increased rainfall and diminished
when rainfall decreased. The 1954-55 and 1964-65 seasons were
exceptions to this rule. This may indicate that the distribution
of rainfall within a season is a factor that also influences the
aldehyde content, but data were not analyzed to ascertain this
The aldehyde content could possibly be maintained at a satis-
factory level by the proper use of irrigation water. Future wide-
spread use of irrigation will undoubtedly result in an improve-
ment in the overall quality of Florida orange oil.

Budwood and Rootstock as Related
to Oil Yield and Quality

Studies by Kesterson and Braddock (99) on oranges and
lemons have demonstrated that budwood has a profound influence
on the total peel oil content of the fruit. The aldehyde content of
three 'Valencia' orange oils obtained from the same budwood on
different rootstocks were 1.26, 1.44, and 1.73% respectively, for
trifoliate orange, sweet orange, and Rangpur lime. Aldehyde
content of citrus oils has been considered one of the more im-
portant indicators of high quality oil, and rootstock apparently
has a pronounced effect on the aldehyde content.


Characteristics and Composition
The physical and chemical properties for coldpressed orange
oil samples, which were secured from seven commercial plants,
are presented in Table 12. Each of the plants used a different
method for expressing the oil. Maximum and minimum values
for the properties of coldpressed grapefruit, tangerine, lemon,
and lime oils produced by the FMC-In-Line Extractor are shown
in Table 13. Approximately 60% of all the oils in Florida are
produced by this method. The other methods of extraction would
bring about property differences for each of these oils similar to
those shown for the coldpressed orange oils in Table 12.
Coldpressed orange, grapefruit, tangerine, tangelo, murcott,
lemon, and lime oils are produced commercially in Florida. These
oils are composed of mixtures of hydrocarbons, oxygenated com-
pounds, and non-volatile residues. The hydrocarbons are pri-
marily terpenes, while the oxygenated compounds are made up
of a variety of compounds-aldehydes, esters, acids, alcohols,
ketones, and phenols. Non-volatile residues consist of resins and
The greatest advance in determining chemical composition of
essential oils has occurred during the past 15 years and involves
the use of gas liquid chromatographic (GLC) methods. The ap-
proximate qualitative and quantitative composition of Florida
citrus oils (13, 14, 101, 103, 104, 105, 201, 202) have been deter-
mined by GLC methods, but need further study and clarification
before these analyses can be used generally for establishing any
new standards.

a-tocopherol Content of Citrus Oils as Related
to Method of Extraction
Data by Waters (193) and Waters et al. (194) have demon-
strated that the type of commercial extraction had a significant
(99% confidence level) influence on the tocopherol content and
evaporation residue of citrus oils. The tocopherol content of mid-
season orange oils followed the order: Brown peel shaver ( x =
216 ppm)> FMC-In-Line (x = 126 ppm)> screw press (x =
104 ppm). The method of extraction influenced both the evapo-
ration residue and tocopherol content of orange oil. The higher
the evaporation residue the higher the tocopherol content. Kes-
terson et al. (101) have previously shown that the oxidative sta-
bility of orange oil was related to evaporation residue. The
higher the evaporation residue the more stable the oil toward


Table 12.--Maximum and minimum values for the properties of coldpressed orange
oil produced by various methods.
Method of
Extraction Pipkin Roll Screw Press Fraser-Brace
No. of Samples 21 123 52
Lb. Oil/Ton Fruit 0.75 to 1.0 3.5 to 5.0 4.5 to 7.5
Max. Min. Max. Min. Max. Min.

Sp. gray.
25C/25C 0.8432 0.8420 0.8426 0.8416 0.8458 0.8441
Ref. id. D 1.4734 1.4718 1.4733 1.4719 1.4743 1.4730

Ref. ind. 10%
dist.n 1.4722 1.4708 1.4723 1.4707 1.4724 1.4703

Difference 0.0013 0.0007 0.0015 0.0007 0.0031 0.0016

Opt. rot. 5 +98.05 +96.64 +97.80 +96.53 +96.30 +94.54

Opt. rot. 10%
Opt. rot. 10%25
dist.25 +98.31 +97.30 +98.65 +97.24 +98.70 +96.96

Difference +1.28 +0.01 +1.41 +0.03 +3.70 +1.51

content, % 2.02 1.63 1.85 0.92 1.65 0.93

Ester content, % 1.01 0.15 1.09 0.04 1.63 0.35

residue, % 2.42 1.07 2.23 1.37 4.93 3.12

oxidation. The alpha, beta, and gamma forms of tocopherol were
found to occur in peel oil, and with few exceptions the predomi-
nant form was alpha. Dewaxing did not result in a significant
loss of tocopherol. However, storage resulted in overall losses up
to 48%. The amount of loss depended upon time and temperature
of storage. Low storage temperatures are required to keep losses
to a minimum. Tocopherols exhibited large variations with re-
spect to season, fruit maturity and variety. Fruit variety in-
fluenced the amount of tocopherol in coldpressed oils and gen-
erally followed the order: grapefruit ( x= 346 ppm), tangerine
( x =200 ppm), tangelo ( x = 88 ppm), lime ( x = 45 ppm), and
lemon (x=41 ppm).


Table 12.-Continued

FMC Rotary FMC-ln-Line AMC Scarifier Brown Shaver
112 237 2 14

2.0 to 3.0 3.0 to 4.5 3.0 to 5.0 3.5 to 6.0
Max. Min. Ma Ma x. Mi Max. Min. Max. Min.

0.8443 0.8420 0.8438 0.8424 0.8449 0.8433 0.8435 0.8427

1.4737 1.4722 1.4731 1.4725 1.4731 1.4728 1.4730 1.4726

1.4727 1.4707 1.4717 1.4715 1.4716 1.4716 1.4723 1.4719

0.0015 0.0010 0.0014 0.0010 0.0015 0.0012 0.0011 0.0007

+97.57 +94.98 +97.08 +95.32 +96.70 +96.36 +97.32 +97.18

+98.73 +96.49 +97.92 +95.74 +98.16 +97.47 +99.11 +98.09

+2.00 +0.00 +1.51 +0.11 +1.80 +0.77 +1.89 +0.80

2.04 1.17 1.96 1.54 1.86 1.86 1.66 0.86

1.34 0.08 -

3.22 1.85 3.08 2.45 4.00 2.80 2.56 2.17

De-Oiler Oils

De-oiler oil is secured as a by-product in the processing of
citrus fruit juice. Some of the citrus peel oil becomes mixed with
the juice as it is extracted by the various types of juice extrac-
tors used in the canneries. An excessive amount of peel oil in the
juice is considered detrimental to the quality of canned juice;
therefore, in most canning plants the oil content of the juice is
reduced to a desirable level by passing the juice through a de-
oiler. The juice is usually flashed in the de-oiler, which is oper-
ated under a vacuum of 11 inches (190F) to 25.5 inches (130F).
A vapor mixture of oil and water is removed and condensed. The


Table 13.-Maximum and minimum values for the properties of coldpressed grapefruit, tangerine, lemon, and lime oils extracted by
the FMC-In-Line Extractor.
Type of Oil Grapefruit''' Tangerinee '1 Lemon (' Limea h
No. of Samples 8 6 52 5

Max. Min. Max. Min. Max. Min. Max. Min.
Sp. grave. 25C/25C 0.8544 0.8506 0.8461 0.8457 0.8480 0.8500 0.8974 0.8642

Ref. ind. n20 1.4767 1.4755 1.4743 1.4736 1.4749 1.4738 1.4907 1.4784

Ref. ind. 10% dist. 20 1.4718 1.4715 1.4725 1.4721 1.4731 1.4725 1.4732 1.4730

Difference 0.0050 0.0040 0.0019 0.0015 0.0018 0.0010 0.0177 0.0053

SOpt. rot. a 25 +93.45 +91.52 +92.45 +91.56 +66.34 +57.82 +46.20 +39.85

Opt. rot. 10% dist. 25 +97.61 +96.94 +96.01 +94.00 +65.34 +55.42 +51.71 +48.33

Difference +5.42 +3.60 +4.45 +1.55 -4.05 -1.28 +10.27 +3.53
Aldehyde content-% 1.56 0.98 1.17 1.12 3.66 1.99 6.66 4.70
Evaporation residue-% 8.60 5.93 4.30 3.63 2.60 1.60 16.67 4.66
UV spectrum CD 0.32 0.19 0.68 0.50 0.48 0.20 1.23 0.99

ML log E 025 g Peak 0.43 0.26 1.28 1.05 0.96 0.49 1.59 0.98
100 cc

Mu 320 318 327.5 325.0 320 312 320 318

":Optical rotation at 20C. 'Aldehyde content-decyl.
1'1 mm light path. 'Aldehyde content-citral.
"10 mm light path. 'Major UV peak only (minor peak occurs at 270 Mu).

Table 14.-Maximum and minimum values for the physical and chemical properties of de-oiler oils (101).
Type of Oil Orange Grapefruit Tangerine
No. of Samples 19 9 2
Max. Min. Max. Min. Max. Min.

Sp. grave. 25C/25C 0.8464 0.8400 0.8539 0.8415 0.8415 0.8407

SRef. ind. n 1.4732 1.4715 1.4746 1.4714 1.4720 1.4716

Opt. rot. a 5 +98.56 +95.92 +96.50 +91.50 +93.67 +91.87

Aldehyde content-% 2.48 1.72 4.06 2.30 1.24 0.95
Ester content-% 1.38 0.22 2.52 0.08 0.35 0.25
Evaporation residue-% 1.24 0.08 3.66 0.19 0.55 0.20

oil is separated from the condensate by decanting or centri-
fuging. Vacuum steam-distilled oils obtained in this manner will
have properties slightly different from atmospherically steam-
distilled oils and will presumably have better flavoring qualities.
It was noted that orange de-oiler oil had an aldehyde content
about 24% higher and an ester content approximately 10% lower
than the corresponding average value for coldpressed oil. Simi-
larly, vacuum steam-distilled oil obtained in the de-oiling of
grapefruit juice was found to run approximately 90% higher in
aldehydes and 60% lower in esters than the expressed oils. It
seemed apparent that additional aldehydes were extracted and
removed from the citrus juice itself by the de-oilers during com-
mercial canning operation. The maximum and minimum values
for Florida de-oiler orange, grapefruit, and tangerine oils as
given in Table 14 are considered typical for high quality de-oiler

Distilled Citrus Oils
In Florida, distilled citrus oils (59) are produced primarily
by passing the underflow from the centrifuges used to produce
expressed oils through a steam stripper operating in the tem-
perature range of 230 to 270F. The hot centrifuge effluent (0.1
to 1.2% oil) is flashed into a long turbulent area where evapo-
ration takes place at a considerable pressure drop. The vapors go
to a condenser and the oil-water mixture is separated in a de-
cant tank. The oil produced from this process has a natural fruit
aroma characteristic of the fruit from which it is made: orange,
grapefruit, tangerine, tangelo, murcott, lemon, or lime (62). Oils
distilled in this fashion can be used by the food and flavor indus-
try. However, the greater volume of these oils end up as d-limon-
ene or citrus stripper oil. The removal of these oils from the
centrifuge effluent greatly reduces waste water handling prob-
lems since d-limonene is a known, potent bacteriostatic material.
Maximum and minimum values for nine samples of steam-dis-
tilled orange oils are shown in Table 15.

Essence Oils
Essence oils are obtained from juice evaporators during the
concentration of citrus juices. The principle of essence (200) or
volatile component recovery from citrus juices is based on va-
porization of a part (25%) of the water present in the juices and
the tendency of this vapor to contain both the oil and the aroma


Table 15.-Maximum and minimum values for the physical and chemical
properties of distilled orange oils (101).
Max. Min. Average

Specific gravity 0.846 0.840 0.842

Refractive index 20 1.4732 1.4715 1.4720

Optical rotation 25 +98.560 +95.92 +97.62

Aldehyde content-% 2.48 1.72 1.99
Evaporation residue-% 1.24 0.08 0.47

and flavor-bearing aqueous components. Concentration and re-
moval of the essence and oil are obtained by use of a stripping
column or flash chamber, a reflux column and condenser, and a
chilled product condenser and receiver. The essence oil floats to
the top of the aqueous essence and is decanted off. Figure 17
is a schematic for a single-stage essence recovery system.
Essence oils are produced commercially in Florida by four
different types of recovery units: 1, Atkins, Citrus Experiment
Station; 2, Redd; 3, Walker; and 4, Cook. Table 16 shows the
physicochemical properties for 15 essence oils analyzed during

Schemotic Single Stoge
Essence Recovery

Cond. Cond. Pump

Row APV Floah
Juice c chamber

C nabate
PD.Pup PD.p To Essence
SStripped Receiver
-JJuice to

Figure 17.-Schematic for a single stage essence recovery system.


Table 16.-Physicochemical properties of orange essence oils (101).
Property Maximum Minimum Average

Sp. gray. 25C/25C 0.8428 0.8403 0.8415
Ref. ind. nD 1.4725 1.4721 1.4723

Opt. rot. a +99.16 +97.68 +98.42
Aldehyde, % 1.86 1.28 1.57
Evap. res., % 1.29 0.34 0.81
Acid no. 0.22 0.11 0.16
Free acid, % 0.06 0.03 0.04
Ester no. before acatylation 3.08 2.94 3.00
% ester before acetylation 1.08 1.03 1.05
Ester no. after acetylation 6.50 5.43 6.06
% ester after acetylation 2.27 1.90 2.12
Free alcohol, % 0.97 0.64 0.84
Total alcohol, % 1.78 1.49 1.66

the 1968-69 season, by all four processes. The aroma and flavor
of these oils are quite different from other orange oils produced
in Florida, having a fruity aroma characteristic of fresh juice.
Essence oils contain 0.5 to 2.0% valencene, a sesquiterpene
not appreciably present in other citrus oils. This terpene can be
recovered and converted into nootkatone (92) and used as a
flavor enhancer.

Juice Oils
During the manufacture of juices for babies or infants, it is
customary to centrifuge the juice in order to lower the oil con-
tent. Our laboratory has examined one sample each of juice oil
prepared from the following types of 'Valencia' orange juices:
1, Brown Reamer and 2, FMC-In-Line Extractors. These oils
possess a flavor and aroma typical of fresh orange juice and quite
different from coldpressed oils. The physicochemical properties
for these oils are summarized in Table 17 and compared with a
typical coldpressed 'Valencia' orange oil.
Data in Table 18 show that juice oils are low in aldehyde
content and high in ester content as compared to coldpressed
oils. The ester content of juice oil is some 7 to 18 times greater
than that of coldpressed oil, and this change in ratio of flavor


Table 17.-Physicochemical properties of oils centrifuged from 'Valencia'
orange juice as compared with coldpressed 'Valencia' orange oil

Type oil Juice Oil Coldpressed Oil
Extractor Brown Reamer FMC-ln-Line FMC-ln-Line

Sp. gray. 25C/25C 0.8427 0.8501 0.8427
Ref. ind. 20 1.4730 1.4740 1.4730

Ref ind. 10% dist. n 1.4723 1.4724 1.4718

Difference 0.0007 0.0016 0.0012

Opt. rot. a 25 +97.22 +90.82 +97.42

Opt. rot. 10% dist. a 25 +99.11 +99.31 +97.71

Difference +1.89 +8.49 +0.29
Aldehyde (decyl), % 0.86 0.72 1.63
Evap. res., % 2.56 10.15 1.79
Acid no. 1.17 1.66 0.50
Free acid, % 0.30 0.43 0.13
Ester no. before acetylation 1.94 11.99 0.27
% ester before acetylation 0.68 4.19 0.10
Ester no. after acetylation 3.83 14.68 3.43
% ester after acetylation 1.34 5.13 1.20
Free alcohol, % 0.52 0.74 0.87
Total alcohol, % 1.05 4.04 0.94

Table 18.-Ratio of the oxygenated components of 'Valencia' juice oils as
compared with coldpressed 'Valencia' orange oil and essence oil

Type Oil Juice Oil Coldpressed Oil
Extractor Brown Reamer FMC-ln-Line Essence Oil FMC-ln-Line

Compound % % % %
Aldehyde 36.5 11.9 46.4 59.6
Ester 28.8 68.9 29.3 3.7
Alcohol 22.2 12.2 23.1 31.9
Acid 12.7 7.0 1.2 4.8
100.0 100.0 100.0 100.0


components is probably responsible for the fruity note in juice
oils. The two juice oils are quite different in chemical composi-
tion, which is undoubtedly due to the difference in the type of
equipment used to express the juice. Essence oil is quite similar
to oil recovered from Brown Reamer juice.

Citrus oils such as coldpressed orange, grapefruit, tangerine,
tangelo, murcott, lemon, and lime find amazingly wide and varied
applications in at least 32 major industries such as beverage,
food, perfume, cosmetic, soap, pharmaceutical, paint, confection-
ery, condiment, ice cream, insecticide, rubber, and textile, and
for the scenting and flavoring of many other types of products.
The most important outlet for citrus oils is the flavor in-
dustry, which regularly consumes substantial quantities of the
natural oils, terpeneless oils, and fivefold concentrates. The latter
are often used in combination with the expressed oils to produce
special flavors or aromas.
De-oiler and distilled citrus oils are used by the food and
flavor industry to impart a citrus taste or aroma to products
where the absence of color is desirable. Essence oils and juice
oils possess a natural fruity aroma and flavor of the fruit from
which they are obtained. These oils can be blended with other
citrus oils to impart a natural fruit-like flavor to products in
which they are used.

Citrus is an especially rich source of two important flavanone
glycosides, hesperidin and naringin. Flavonoids are widely dis-
tributed in nature and have been the subject of a book by Har-
borne (64). They have been sub-classified as flavones, flavanones,
flavonols, isoflavones, etc., all of which have a specific chemical
configuration. Another small group of flavonoids, called biofla-
vonoids, has been shown to have physiological and biochemical
Since discovery in 1936 (163) that certain plant flavonoid
extracts had an unknown but curative factor not to be found in
other vitamins, there has been a profusion of literature on bio-
flavonoids sufficient to confound even trained minds. The term
vitamin P was suggested for the factor that improved capillary
fragility, but the dosage required in some tests suggested a
pharmacological action rather than that of a vitamin. In 1950,


it was recommended that the term vitamin P be discontinued.
Today, after years of study, there is still no specific chemical or
bioassay procedure for this biological factor, but its therapeutic
importance to many diseased capillary conditions has been rec-
ognized. Citrus fruit continue to be regarded as an important
source of bioflavonoids.

Abundant quantities of hesperidin are found in the blossom,
the small unripe fruit, and the peel of the mature sweet orange;
however, its exact function is not understood. It is found also in
lemons, mandarins, bitter oranges and citrons. Each mature
sweet orange has almost 1 g of hesperidin-like material of which
roughly half can be recovered by commercial procedures. On this
basis, 29 million pounds could have been recovered from the
oranges processed in Florida during the 1975 season. Domestic
production, however, is of the order of 100,000 pounds annually.

Distribution in Sweet Oranges
The proportion of hesperidin in the component parts of a
mature orange were 32 to 50% in the rag and pulp, 30 to 50%
in the albedo, 12 to 23% in the flavedo, and 1.5 to 6.0% in the
juice (68). A significantly greater amount has been found in the
stylar end than the stem end of the fruit (61).
There were only small differences between the hesperidin con-
tent of 'Valencia,' 'Hamlin,' 'Parson Brown,' and 'Pineapple'
oranges throughout a season, although the latter variety had the
most. During maturation, total hesperidin content reached a
maximum before the fruit had an equatorial diameter of 2 inches.

Recovery of Hesperidin
The easiest method of isolating hesperidin is to extract
chopped citrus peel with hot methanol and then allow it to
crystallize as suggested by Horowitz (89). Commercial practice,
however, has found it more advisable to make an alkaline water
extraction with hydrated lime. The hesperidin in chopped orange
peel is dissolved slowly under alkaline conditions that can be
maintained by frequent hydrated lime additions. After sufficient
reaction time, the dilute hesperidin solution is separated by pres-
sing from the insolubles, is acidified, and is allowed to crystallize.
After a day or two, the crude product is filtered off and dried. At


least four patents (16, 80, 81, 82) have been granted on this
technique. Two products are produced for the trade, hesperidin
complex that has a minimum analysis of 40% and a purified
product with a minimum assay of 90% hesperidin.
When extracting mature oranges, it is possible to recover the
equivalent of 8 to 10 pounds of pure hesperidin per ton of peel
residue. If, however, whole immature 'Valencia' fruit of 1.2-inch
average equatorial diameter are extracted, as much as 80 pounds
of pure hesperidin per ton of fruit can be recovered.
Experience has shown that better yields of hesperidin are
procured by recycling extraction liquid by using 'Pineapple'
orange peel, by chopping the peel finely, and by extracting im-
mature fruit. The ideal extracting pH is highest for immature
fruit and proportionately lower with fruit of more advanced
maturity. Effective extraction requires a minimum pH of 11.1.
Hesperidin isolated by commercial procedures varied in purity
between 90 and 39%, being greatest with the most immature
fruit. Highest purity was obtained by those conditions that en-
couraged best yield.

Hesperidin was purified readily by recrystallizing from a
formamide solution (146), but was purified commercially by dis-
solving the crude product in an alkaline alcohol water solution.
A 50% isopropyl alcohol concentration was the most effective
compromise for best filtration rate and hesperidin recovery. The
purified product was isolated by subsequently reducing the alka-
linity to pH 8.5, crystallizing, and filtering.
The recovery of hesperidin was improved significantly by ex-
tending the crystallization period (77), but the additional time
required was impractical. If product purity required improve-
ment, it was improved sufficiently by washing or by reslurrying
the crystallized product with volumes of very hot water.

The Davis method (43) is the analytical method most often
used for hesperidin analysis. Although insufficiently specific, it is
as adequate as other methods. When eight analytical techniques
for hesperidin and other flavonoids were evaluated (74), the
Lorenz and Arnold (121) procedure was found to be unsuited,
while an azo-coupling method (74) was the most sensitive. A
methoxy test (11) was sometimes useful, as was the gravimetric


procedure (34). The Arcangeli-Trucco method (9) was the most
tedious, while a UV technique (73) was the most specific of the
photometric procedures. Paper chromatography was very specific
but lacked sensitivity. The authors have concluded that the Davis
method offered more advantages in routine assaying. This deter-
mination was more sensitive when modified to a lower wave-
The bioassay of hesperidin and other flavonoid extracts capa-
ble of improving capillary permeability has been carried out with
many different animals. The guinea pig has been the most satis-
factory animal, although even it was not entirely adequate (15).
Less accepted than the animal tests, which are unsuited to
routine analysis, have been the alternative short-cut methods of
biological assay, such as: measuring bleeding time, inhibition of
succinoxidase or hyaluronidase, toxicity protection against ar-
senicals, and others mentioned by Scarborough et al. (164).

Hesperidin has found its greatest use as a therapeutic agent
in the pharmaceutical industry. Patents were granted for the
conversion of hesperidin to a carboxylate derivative by Ohta
(138), to an alkylated chalcone by Wilson (198), to a water-
soluble alkoxyl substituted chalcone glycoside by Wilson (197),
and to a methylene carboxy chalcone by Hart (65). Patents were
granted to Hendrickson and Kesterson (75) for the preparation
of an azo dyestuff and to Toulmin (177, 178) for conversion to
azo dye wood stains.

Naringin occurs as the predominant flavonoid in the grape-
fruit (Citrus paradisi MacFayden) and in the less seen shaddock
or pummelo (Citrus grandis [Linn.] Osbeck). Naringin is dis-
tinguished readily from hesperidin by its extreme bitterness.
This bitterness is sometimes imparted to grapefruit products.
There was a potential of 11 million pounds of naringin in Florida
grapefruit processed in 1974, but none was recovered.

Distribution in Grapefruit
The distribution of naringin on a percentage basis in the com-
ponent parts of mature grapefruit was 50 to 60% in the albedo,
30 to 40% in the rag and pulp, 5 to 10 0% in the flavedo, and 1 to


3% in the juice (110). More naringin was found in the seedy
grapefruit varieties, but only by virtue of their larger size.

Recovery of Naringin
Naringin can be recovered by methods similar to those for
hesperidin. When alkali is used to solubilize the naringin, a lower
pH (8.8 to 9.0) is needed than when recovering hesperidin. If the
grapefruit peel is sufficiently immature, it is possible to release
80 to 90% of the recoverable naringin with a plain water extrac-
tion. Extracts are treated later with alkali to degrade the pectin
that inhibits naringin crystallization. The water-extracted peel
is ideally suited for the further recovery of pectin.
When immature whole 'Marsh' grapefruit are extracted, the
equivalent of 52 pounds of pure naringin can be recovered per
ton of fruit. Fruit in this special case should have an equatorial
diameter not greater than 1.5 inches. Peel of mature grapefruit
can yield the equivalent of 4 to 8 pounds of naringin per ton.
There are, however, more problems in crystallizing naringin
than hesperidin, and yields are often disappointing.

Crude naringin is purified most easily by the procedure of
Hendrickson and Kesterson (76) by dissolving the crude naringin
in boiling anhydrous isopropanol. The concentrated naringin
solution (approximately 9%) is filtered from its insolubles and
is allowed to crystallize. Seeding is required sometimes. The
crystallized naringin is separated by filtering and is washed with
more isopropanol before drying. A purified naringin of 98 to
100% purity is produced by this technique. Solvent costs are
reduced by recycling extraction alcohol without much loss in
product purity.

The analytical techniques for naringin closely resemble those
for hesperidin. A comparison of the sensitivity of the more
common analytical techniques has been published by Hendrickson
and Kesterson (76).

The characteristic bitter taste of naringin has been used to
advantage in the preparation of beverage drinks and to enhance


the piquant flavor of high-class confections. Pulley et al. (149)
have described a procedure for recovering the valuable rhamnose
fraction of the naringin molecule. Hendrickson and Kesterson
have a patent (75) on the manufacture of azo dyes from narin-

Dihydrochalcone Sweeteners
The dihydrochalcones of the naturally occurring citrus fla-
vanones naringin and neohesperidin were reported by Horowitz
and Gentili (85, 87, 88) to be intensely sweet. These bitter fla-
vanone glycosides have as their sugar component the disaccharide
neohesperidose. The tasteless flavanone glycosides (hesperidin)
have as their sugar component the isomeric disaccharide ruti-
nose. Neohesperidose and rutinose are composed of one molecule
each of L-rhamnose and D-glucose. In neohesperidose, the rham-
nose is attached to the C-2 hydroxyl group of glucose. In both
cases, the glucose is linked to the flavanone aglycone when the
disaccharides are glycosidically bound. The bitter and tasteless
flavanone glycosides are identical except for the point of attach-
ment of rhamnose to glucose. Consequently, the structure is most
important in determining bitterness or tastelessness in this
group of compounds.
According to Horowitz and Gentili (86), the sweetness of the
dihydrochalcones is many times greater than that of sugar.
When compared with sugar, the sweetness is slow in onset, per-
sistent, and characterized by some as having a licorice-like qual-
ity. Sweet dihydrochalcones have a cooling sensation, frequently
described as a menthol-type after taste (Krbecheck et al. 117).
Efforts to synthesize a sweet dihydrochalcone without this taste
sensation have not been entirely successful. Inglett et al. (93)
and Horowitz and Gentili (86) have compared the relative sweet-
ness of the dihydrochalcones with sugar and saccharin as shown
in Table 19.
The dihydrochalcones are not expected to replace the use of
sugar, but a specialty market may be created where these unique
flavor properties can be utilized for specific requirements.

Miscellaneous Flavonoids
Recently, attention has been given to some of the less known
flavonoids of citrus. Jones et al. (97) have reported that the
natural flavonoid tangeretin has very high cytostatic potency


Table 19.-Dihydrochalcone sweetness value in comparison to other sweet-
eners (86).
Sweetener Sweetness Rating

Sucrose 1
Saccharin 330- 360
Naringin dihydrochalcone 330- 360
Hesperidin dihydrochalcone glucoside 330- 360
Neohesperidin dihydrochalcone 1000-1200

against the zebra fish embryo, while Freedman and Merritt (56)
have demonstrated that nobiletin possesses strong anti-inflam-
matory activity. Tangeretin and nobiletin are known to occur
in tangerines (Citrus reticulata, Blanco) (89), and nobiletin and
sinensetin were found also in peel of 'Valencia' orange (174).
Robbins (150, 151, 152, 153) investigated flavonoids for ac-
tivity on erythrocyte aggregation and sedimentation in blood.
Among the most active are tangeretin, nobiletin, and sinensetin.
Flavonoids act to maintain suspension of the formed elements
in plasma, thereby inhibiting the apparent spontaneous blood
cell adhesion occurring in normal subjects and the increased
blood cell clumping accompanying disease, trauma and stress.
Certain citrus bioflavonoids are natural and potent anti-throm-
bosis agents. Nobiletin was found to be more effective than
heparin in preventing the death of rats from induced thrombosis.
The significance of blood cell aggregation is that it interferes
with micro-circulation causing a variety of adverse effects and
promotes thrombosis and embolism of large vessels. This sug-
gests a dietary role for flavonoids by evidence of a widespread
low-level blood cell aggregation in apparently healthy subjects,
which is inhibited by flavonoids that are normal components of
citrus fruits.
For many years, citrus molasses has been solvent-extracted
to yield a concentrate which is refined to a dried, therapeutically
active product. It is sold in the pharmaceutical trade, and ac-
cording to one related patent (170) is a bioflavonoid mixture of
three substances similar to quercitrin, eriodictyol, and hesperidin.

Citrus seeds have long been recognized as a source of edible
oil with characteristics suitable for human consumption and food


use. At the turn of the century, German researchers determined
many of the chemical and physical properties of the oil and de-
scribed the crude oil as having an intense bitter taste due to the
presence of limonin (143).
It has been an industrial practice to include the seeds from
processed citrus fruit with the peel and pulp portion during the
production of dried cattle feed. However, the amount of seeds
found in the feed is in no way uniform from batch to batch,
since some of the varieties processed have few or no seeds ('Ham-
lin' and 'Valencia' oranges, 'Marsh' grapefruit). Since the seeds
contain valuable oil and protein suitable for human consumption,
it would be much more profitable if they were processed sepa-
rately for this utilization and not included in feed for livestock.
At this writing, no citrus seed oil or meal is produced com-
mercially in Florida, the last manufacturing operation having
ceased production during the 1970-71 season. However, there is
current interest within the citrus industry to produce these
specialty products.

Seed Recovery
A novel procedure for the separation of citrus seeds from
refuse material has been developed by W. A. Kirk (113) of the
Imperial Citrus By-Products Corp., Lakeland, Florida (now de-
funct). This method is preferred since whole refuse consisting of
peel, rag, pulp, and seeds-or, preferably, a mixture of pulp and
seeds-can be separated. The refuse material is transferred by
a screw conveyor to a scrambling device, which throws and dis-
tributes the material evenly onto a slanted (300 slope) moving
belt. At the instant of contact, the seeds bounce off the belt,
striking a baffle which diverts them into a storage bin. The de-
scending refuse is collected at the end of the conveyor. Depend-
ing on the nature of the refuse, wet or dry, a seed removal
efficiency of some 60 to 80% is effected, the most efficient separa-
tion coming from relatively dry refuse. The primary advantage
of this system is a relatively low initial cost, permitting the
removal of seeds without creating the waste water pollution
problem normally encountered in the separation of seeds by
screens or finishers. A sufficient quantity of lime (0.15 to 0.25%0
Ca(OH).) is added to the seeds in the storage bin to prevent
them from solidifying (gel formation). The limed seeds are nor-
mally transported by truck to a central collection point where
they are dried, stored, or processed. Drying is performed in a
conventional citrus feed mill dryer at exit gas temperatures of


Table 20.-Percentage (wt/wt) of seeds in citrus and the related percentage in the corresponding dried pulp for a season (28).
Seeds in Grapefruit Seeds in Oranges
Variety and Variety and
Month of Season Whole Dried Month of Season Whole Dried
fruit (%) pulp (%) fruit (%) pulp (%)

Duncan Pineapple
October 6.8 18.7 October 5.2 14.2
December 4.8 15.2 December 3.2 11.2
February 4.3 13.9 February 3.1 11.2
April 2.9 11.2 April 2.7 10.2

Foster Pink Parson Brown
October 5.0 10.4 October 3.5 9.5
December 4.1 11.5 December 2.4 7.5
February 3.1 11.1 February 2.2 8.5
April 2.6 10.9 April 1.7 7.0

Marsh Valencia
October 0.5 1.7 October 1.2 3.5
December 0.3 1.9 December 0.8 3.2
February 0.3 1.8 February 0.7 3.2
April 0.3 2.2 April 0.7 3.2

about 225F. At this temperature, darkening of the seeds is min-
imized, resulting in a lighter colored oil.
The percentages of seeds in the whole fruit and pulp are gen-
erally higher for immature fruit and lower for mature fruit
(Table 20). Variation in the juice weight is responsible for this
difference since the seed weight is rather constant throughout
a season (28).

Seed Oil Composition
Following seed recovery and dehydration, the dried seeds may
or may not be passed through a roller mill to flake and break
apart the hulls, which are removed by screens. Depending on the
previous step, the kernels or whole seeds are pressed mechan-
ically at high pressures in an oil expeller. A turbid oil is recovered
that is clarified in a plate and frame press.
Unrefined citrus seed oil has been sold. This oil is not changed
noticeably in appearance by refining, but it does lose the ex-
tremely bitter taste that at one time almost precluded further
consideration of the product. Refining is carried out by treating
the seed oil with sodium hydroxide solution in a ratio that is
calculated from analysis of the free fatty acid content (1). The
mixture of alkali and oil is stirred and warmed, and the emulsion
so formed breaks in about 10 minutes at 45C.
Percentage of oil in dried citrus seeds is variable and depend-
ent upon fruit maturity. Typically, the oil content of dried 'Pine-
apple' orange seeds varied from 30.2 to 45.2%, while oil content
of dried 'Duncan' seeds varied from 29.2 to 37.3%. Highest oil
content usually coincided with the optimum maturity needed for
processing. Van Atta and Dietrich (187) found 34.2% oil in dry
'Valencia' orange seeds; the kernels alone had 55% oil. The oil
contents of grapefruit, lime, lemon, and orange seeds were stated
by Jamieson (96) to be respectively 30%, 31 to 40%, 30 to 35%,
and 40 to 45%.
Citrus seed oil contains considerable quantities of the poly-
unsaturated fatty acids, linoleic and linolenic acids. The degree
of unsaturation for the various cultivars is exemplified by re-
fractive index and iodine values in a scatter diagram (Fig. 18).
Figure 18 indicates orange seed oil to be the least and lemon
seed oil to be the most unsaturated.
The major fatty acids of various citrus cultivars are listed in
Table 21 (70, 71, 72, 135, 175). The orange seed oils all have
similar compositions, as do the grapefruit. Distinguishing fea-
tures are the generally higher palmitic acid content of the grape-


C 00

G Lemon

S1.470 Mandarin

F20 Grapefruit
") 1.469 00

S Orange

1.468 .
90 100 110 120
Iodine Value
Figure 18.-Unsaturation of citrus seed oils expressed by refractive
index and iodine value.

fruit, lower linolenic acid content of oranges, more linoleic acid
found in mandarin-types, and greater quantities of linolenic and
lesser amounts of palmitic and oleic acids in lemon and lime seed
oils. Additionally, calamondin, kumquat, and Meyer lemon seed
oils were found to have much greater quantities of palmitoleic
acid than seed oils of other varieties (Braddock and Kesterson,
28). The presence of significant amounts of linoleic and linolenic
acid in the seed oils of citrus may be deterrent if long-term stor-
age stability is required.

Table 21.-Range of fatty acid composition in Florida citrus seed oils (28).
Component acids, %
Seed Type Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic
Oranges 26-31 0.1 3-5 24-28 35-37 2-4
Grapefruit 26-36 0.1-0.3 1-4 18-25 32-40 3-6
Mandarins 22-30 0.1-1.0 2-5 20-25 37-45 3-5
Lemons 20-24 0.1-0.3 2-4 26-31 31-38 8-12
Limes 24-29 0.1-0.5 3-5 20-22 37-40 6-11


Seed Meal Composition
The dry, oil-extracted meal obtained during the oil manu-
facturing operation has a high protein content. The composition
of the press cake meal obtained in the preparation of grapefruit
seed oil is presented in Table 22. In addition, Ammerman et al.
(6) found 16.2% protein in the whole seeds, 19.5% in the kernels,
and 6.1% in the hulls. When fed to lambs as 88% of the total
protein in the ration, the protein of citrus seed meal was equal in
digestibility and biological value to the protein of soybean meal.
The amino acid composition of seed meal has been determined
(31) and is listed in Table 23. When values for five amino acids
important in livestock feeding and animal nutritution are com-
pared with soybean, the following ratios of the amino acids in
orange seed to soybean are obtained: glycine 1.2 cystine 1.3,
methionine 1.4, lysine 0.45, and tryptophan 1.6. For animal feed-
ing, the quantities of glycine, cystine, methionine, and trypto-
phan in citrus seed meal would be an important plus. Similarly,
the lower amount of lysine would be a deterrent.
The data in Table 23 indicates some differences if one com-
pares the amino acid composition of orange and grapefruit seed
meals. Notably, the amounts of cystine and methionine were ap-
proximately 1.5 times higher in the grapefruit than in the orange
seed meal, but orange seed meal had about 1.6 times more tryp-
tophan than grapefruit. The values for total sulfur amino acids
of citrus seed meal are higher than for protein from many com-
mon seeds, nuts and grains (179).
There is concern that removal of seeds from citrus pulp would
lower the protein content of cattle feed to the point of not
passing the guaranteed protein analysis (6%). This is not neces-
sarily true, and data have been presented by Braddock and Kes-

Table 22.-Percentage composition of grapefruit seed press cake (36).
Item Content (%) Item Content (%)
Moisture 3.4 SiO2 0.08
Ash 4.0 S 0.09
N as NH:i 4.2 Ca 0.35
N as protein 21.6 Mg (MgO) 0.39
Crude fat 14.0 NaCI + KCI 2.48
Crude fiber 26.5 Phosphates 0.55
Fe 0.001


Table 23.-Amino acids of citrus seed meal and soybeans.
Mg Amino Acid/g Nitrogen in Product
Amino Acid Orange Grapefruit Soybean*

Aspartic acid 548 560 731
Threonine 186 181 241
Serine 239 290 320
Glutamic acid 1594 1623 1169
Proline 256 253 343
Glycine 322 272 261
Alanine 231 230 266
Cystine 110 174 83
Valine 307 333 300
Methionine 112 165 79
Isoleucine 219 224 284
Leucine 394 446 486
Tyrosine 168 166 196
Phenylalanine 306 296 309
Lysine 178 175 399
Histidine 128 108 158
Arginine 695 596 452
Ammonia -
Tryptophan 125 79 80
"Amino acid values for soybean from reference (179).

terson (28) showing that removal of all seeds from commercial
'Valencia' pulp could lower the protein content by only 0.4%.
The meal may be added back to the dried pulp after oil extrac-
Similar reasoning could be presented relative to the concern
that removal of the seeds from dried pulp would lower the fat
content sufficiently to cause failure of a feed to pass the guaran-
teed minimum fat analysis. It has been shown that 65% of the
fat in dried citrus pulp is derived from sources other than seeds,
and that removal of seeds from 'Valencia' pulp would cause the
fat content of the dried pulp to be reduced only about 1.1% (28).
The above discussion relates to the fat and protein contents
of dried pulp from 'Valencia' oranges. The authors agree that the
percentages of fat and protein attributed to seeds in the pulp
will be higher for the more seedy varieties. Complete removal


of all seeds from the pulp of these seedy varieties may cause the
fat or protein content to be lower than the guaranteed analysis.
However, the most efficient commercial process for seed recovery
from pulp can obtain only 60 to 80% of the seeds present, leaving
sufficient seeds so that the pulp can meet the guaranteed analysis
for fat and protein.

Refined citrus seed oil is bland and pale yellow in color and
with proper processing could be utilized in much the same way
as the oil of other seeds, such as soybeans and cottonseeds. The
refined oil may be used as a salad or cooking oil, but would need
partial hydrogenation for suitable shelf life, primarily because
of its linolenic acid content. With hydrogenation, the oil could
also be manufactured into margarines (7) and shortenings.
Production of a line of specialty fat products such as mayon-
naise and salad dressings could be made from citrus. For mayon-
naise production, refined seed oil which had not been bleached
would be desired since the yellow color of the oil would give the
desired color in the finished products.
Utilization of the oil and defatted meal flour as a beverage
clouding agent has been proposed (102), and a patent has been
issued. As previously mentioned, the defatted meal and hulls
from the oil processing operation may also be added back to the
pulp. Table 24 shows the estimated annual yield of dried Florida
citrus seed by-products, including crude oil, meal, and hulls.
These data were calculated on the basis of the actual number of
boxes of each variety processed during the 1974 season (191.6
million boxes total), and represents the potential yield of seed
oil, meal, and hulls only if all available seeds were processed for
these products. Table 24 shows potential yields of 33, 46, and 25
million pounds of seed oil, meal, and hulls, respectively, calculated
from 1974 processing data (53).
Glasscock et al. (60) showed citrus seed meal to be as val-
uable as cottonseed meal in meeting protein requirements for
steers. Driggers et al. (48) found citrus seed meal to have a fac-
tor that was toxic to chickens.

The component parts of citrus fruits, flavedo, albedo, mem-
brane, juice vesicles, and core all contain varying quantities of
pectin, mostly as protopectin. Generally, there is a significant


Table 24.-Estimated annual yield of dried Florida citrus seed by-products.
Millions of Ibs.
Oil Meal Hulls
Early and midseason 20.6 28.4 15.5
Valencia 6.6 9.1 4.9
Temple 0.7 0.9 0.5

Duncan 4.7 6.5 3.5
Marsh 0.3 0.4 0.2

Tangerines 0.3 0.4 0.2
Tangelos 0.1 0.2 0.1

variation in the quantity of pectin in these tissues with fruit
maturity. Large variations also occur among the different fruit
varieties in the quantity and types of pectic constituents. Nor-
mally, lemons, limes, grapefruit, and oranges are the citrus
varieties used for most pectin production.

In studying the pectin content of Florida grapefruit and
oranges, Gaddum (58) found: 1, the percentage of total pectic
compounds in the albedo and pulp remains constant over much
of the growth period; 2, the percentage of water-soluble pectins
rises in these tissues to a maximum just prior to the decline in
total pectic content; and 3, the rate of protopectin conversion
into water-soluble pectins is greater in the pulp than the albedo.
California grapefruit peel and rag contained 3.93% pectin as
calcium pectate according to Poore (144). His individual an-
alyses of Florida peel and rag showed, respectively, 3.19 and
3.56% pectin as calcium pectate.
Pectin, as calcium pectate, was determined on a wet and dry
basis by Rouse (162) in the component parts of seven varieties
of mature citrus fruits. On a dry.basis, the rag component had
the highest percentage of pectin in 'Dancy' tangerine, 'Pineapple'
and 'Valencia' oranges, and 'Duncan' grapefruit. Only in the
'Hamlin' and 'Temple' oranges was the albedo the most abundant


source of pectin, while 'Marsh' grapefruit was unusual in having
the highest percentage of pectin in the flavedo.
The effects of maturity upon the physical and chemical values
of extracted pectins from peel, membrane, and juice sacs of 'Va-
lencia' oranges were investigated by Rouse et al. (158). Since
water-soluble pectin fractions always were included, there were
only minor maturity differences. The pectins extracted from the
membrane fraction were highest in yield, jelly grade, purity,
and relative viscosity. Jelly grade for the extracted pectins de-
creased slightly with maturation, but increased later. The aver-
age jelly grade for peel, membrane, and juice sacs was 206, 314,
and 222, respectively. Pectins from the seeds had no jelly grade.
The pectin content of 'Valencia' (159) and 'Pineapple' (157)
oranges of Florida has been studied in detail by Rouse et al. The
percentage of pectin found to be water-soluble, ammonium ox-
alate-soluble, and sodium hydroxide-soluble was determined for
five components of each variety at different stages of maturity
during two seasons. It was found that the ammonium oxalate-
soluble pectin content of the 'Valencia' orange components in-
creased slightly during maturation. This trend was not detected
in 'Pineapple' oranges. Protopectin was greatest in the mem-
brane component of each variety and generally decreased in the
latter part of the sampling period. The five components into
which fruit were separated for study were peel, membrane, juice
sacs, seeds, and juice. The average percent by weight of these
components in 'Pineapple' oranges were, respectively, 22.7, 14.2,
21.9, 3.5, and 37.7. The percentages for 'Valencia' oranges were
20.8, 12.0, 23.7, 0.8, and 42.7, respectively.

Processing Procedure
A general processing procedure for the commercial produc-
tion of pectin from citrus peel has been described by Sinclair
(169). He outlined, first, the preparation of the peel for extrac-
tion by removing the oil, mincing and leaching with water to re-
move soluble sugars and other substances. After leaching, the
protopectin in the peel is solubilized by acid hydrolysis, the solu-
tion is filtered, and the pectin is precipitated by dilution with
isopropyl alcohol. This precipitate is purified and dried to a final
product moisture content of 6 to 10%.
Many procedures exist for extraction and recovery of pectin
from citrus peel. One recent procedure reports the use of ion
exchange resins and critical pH control to produce better yields


and higher gel grades than traditional mineral acid extractions
(Huang (90)).
Following extraction, recovery, and purification, the authors
estimate yields of 2.0 pounds per 90 pound box ('Valencia'
oranges) and 2.2 to 2.5 pounds per 85 pound box ('Duncan'
grapefruit) of 150 grade pectin.

Pectin Pomace
At one time, a type of pectin pomace was manufactured in
Florida (8) by methods described by Pulley et al. (147). A re-
fined pectin pomace of better than 50 grade was produced from
citrus peel residue by scalding, leaching, pressing, and drying.
This product was used by jam, jelly, and marmalade manufac-
The product called pectin pomace made today in Florida is
produced primarily from lemon and lime peel. The waste peel
from the juice extractors is chopped in a shredder, leached with
hot or cold water to remove some of the soluble components, and
dried in the same type rotating drum, direct-fired dryers as used
for manufacturing citrus pulp cattle feed. Dryers should be main-
tained at exit gas temperatures of less than 250F to minimize
darkening and prevent degradation of the product. Product tem-
peratures should not exceed 140 to 145F. The final product (8
to 10% moisture) is usually bagged in 100 pound sacks and
shipped to out-of-state or foreign pectin manufacturers for proc-
essing into pectin products, as there are currently (1976) no
pectin manufacturers in Florida.

The primary uses of citrus pectin are in the production of
jams, jellies, and preserves. Pectins are also used as thickeners
and stabilizers in foods such as puddings and processed milk
products and salad gels. They are used in the manufacture of
confections and as emulsifying agents in salad dressings and
mayonnaise. Other uses for pectin have been described by Ker-
tesz (111), who mentioned uses of pectin as a hemostatic agent
for wound treatment, as a blood plasma substitute, as a treat-
ment for gastrointestinal disturbances, and in pastes, cosmetics,
soaps, etc.


Citrus juice finisher pulp is composed largely of ruptured
juice vesicles, which still contain some juice and soluble solids.
It has been found economical to recover these materials as liquids
by washing the juice sacs with water. These recovered wash
liquids are now termed "pulp wash" by the industry. The pulp
wash is concentrated by evaporation and the resulting product
is called "pulp wash concentrate."

Processing Procedure
Some aspects of processing technology and equipment con-
cerning soluble solids recovery and pulp washing have been dis-
cussed by Belk (23) and McKinnis et al. (122). A general pro-
cedure used to recover soluble solids and remaining juice from
juice sacs is illustrated in Figure 19 and is described as follows.
The juice sacs are recovered by finishing once extraction is
complete and then moved by screw conveyors to the washing
Washing juice sacs occurs as outlined in the flow diagram
(Fig. 19). Usually, the juice sacs are mixed with water in a series
of mixing tanks and finishers designed to take advantage of the
concentrating effect of countercurrent distribution of the wash
The wash liquid of highest soluble solids content goes to a
surge tank, where if necessary, a small amount of concentrated
wash liquid is blended to raise the degrees Brix sufficiently to
feed the evaporator. It is sometimes necessary to centrifuge diffi-
cult-to-handle wash liquids from the final finisher to remove ex-
cessive particulate material prior to evaporation.
The soluble.solids of pulp wash liquids are concentrated in
evaporators in the same manner as the juice. Pump-out from the
evaporators is close to 500 Brix, because the concentrated pulp
wash is usually traded commercially as a 500 Brix product.
Use of commercially available pectolytic enzymes has been
advocated to increase the yield of soluble solids and reduce vis-
cosity of pulp wash liquids during processing (Braddock and
Kesterson (25, 27). The yield of soluble solids recovered during
pulp washing increased by 20% when enzymes were added to the
pulp prior to the washing operation. Addition of enzymes to
previously recovered high viscosity pulp wash successfully re-
duced the viscosity, enabling concentration to very high (65 to
700 B) solids content.



r 9 t l u r pLU si





Figure 19.-Flow diagram of a theoretical countercurrent pulp washing

Data were published by Olsen et al. (139) which illustrated
Brix/acid ratios, sucrose and reducing sugars, pH, pectic con-
stituents, turbidity, pulp content, ascorbic acid, viscosity, and
flavonoid content of experimental and some commercial samples
of pulp wash liquids and concentrates. Characterization of pulp
wash continued with publication of quality data by Huggart et al.
(91), examination of pectic substances by Rouse et al. (160),
microbiology (Hill and Patrick (83)), and comparison of pulp
wash and orange concentrate by Wenzel (195).
Generally, pulp wash concentrates are similar in composition
to orange juice concentrates. In fact, it is not uncommon for
juice extraction overages to end up in the pulp wash during
commercial operations. True pulp washes in general do not have
the good flavor or color of juice concentrates.
Some characteristic values for commercial pulp wash ob-
tained from various sources are listed in Table 25. Many of the
values fall in ranges acceptable for juice, but generally this prod-
uct does not have all the criteria of juice. Pulp wash viscosities
may be quite high, contributing to problems associated with


Table 25.-Average composition of commercial pulp wash concentrates from
Characteristic Minimum Maximum Average
"Brix 50 50 50
Acid (% citric) 2.1 3.42 2.83
Ratio 14.6 23.8 17.7
Glucose (g/100 ml) 5.5 6.3 5.9
Fructose (g/100 ml) 10.9 14.1 12.5
Sucrose (g/100 ml) 20.6 28.3 24.5
Total pectin (mg/100 g) 50.5 1404 85
Ascorbic acid (mg/100 ml) 145 156 151
Protein (g/100 ml) 0.01 0.04 0.02
Flavonoids (mg/100 ml) 116 971 589
Color score 23 36 27
Apparent viscosity (CPS) 1100 Gel 9500

gelation. Color scores are significantly low enough that, for the
most part, pulp wash color is poor. In fact, color measurements
were used experimentally by Petrus and Dougherty (142) in at-
tempts to distinguish pulp wash concentrates from true juice
The composition of pulp wash is such that, under certain
instances, it may be included as a component of the product called
concentrated orange juice for manufacturing (171). Under Fed-
eral law, the product, frozen concentrated orange juice, may con-
tain water extracts of excess pulp (183). However, in Florida,
the addition of pulp wash solids to frozen concentrated orange
juice is prohibited.
For oranges, there are approximately 4 to 8 pounds of juice
sacs per 90-pound box of fruit. The authors have found that pulp
washing can recover from 125 to 150 pounds solids per ton of
pulp or about 0.3 to 0.4 pound solids per box of oranges.

Pulp wash concentrates are used in a variety of food and
beverage products. In Florida, where the wash solids are ex-
tracted from the pulp coming from the same lot of fruit as the
juice, they may be included in concentrated orange juice for
manufacturing (171). As such, these solids may eventually be
components of certain processed juices and juice drinks. Pulp
wash concentrates may also be used in beverage bases for canned
or bottled ades (fruit drinks and punches). In beverages, pulp
wash concentrate is often used to impart turbidity or cloud to


the product. Pulp wash concentrates are also used in popsicle

The production of three traditional by-products of citrus
processing-dried pulp for cattle feed, molasses, and essential
oils- is firmly established in Florida. However, if the pulp,
sugars, etc. used to make animal feeds were converted into hu-
man foods, and if the essential oils were fractionated and mar-
keted as chemicals, the value of these products would be greatly
enhanced. Many specialty products are possible from citrus fruits
and citrus wastes; some of these possibilities will be described
in the following sections.

Citrus Sections and Salads
Federal (USDA) standards define canned grapefruit (182),
"U. S. Grade A" grapefruit sections, as a canned product pre-
pared from clean, sound and mature grapefruit (C. paradise
MacFayden). The product has an average drained weight of not
less than 53% of the water capacity of the container, of which
not less than 65%/wt of the drained grapefruit consists of whole
or practically whole segments; has a good color; is practically
free of defects; has a good character; has a good flavor and odor;
and scores not less than 90 points. The product is sufficiently
processed by heat to assure preservation in hermetically sealed
Canned grapefruit and orange for salad (181), commonly
known as canned citrus salad, is prepared from sound, mature
grapefruit (C. paradisi MacFayden) and sound, mature oranges
of the orange group (C. sinensis). The fruit ingredients have
been properly washed, segmented, and cored, and seeds and
major portions of membrane have been removed. The product
is packed with a suitable packing medium which may be water,
fruit juice, orange juice, nutritive carbohydrate sweeteners, arti-
ficial sweeteners, or any other safe and suitable ingredients
permissible under the Federal Food, Drug and Cosmetic Act.
The product is sufficiently processed by heat to assure preser-
vation in hermetically sealed containers.
Frozen grapefruit (185) is prepared from the matured fruit
of the grapefruit tree (C. paradisi), after the fruit has been
washed and peeled, and has been separated into segments by


removing the core, seeds, and membrane. It may be packed with
or without packing media, frozen, and stored at temperatures
necessary for the preservation of the product.
The parameters and process for preparing citrus sections
will be discussed as follows.

Storage of Fruit
Fruit are normally stored and cured in holding bins for 4
to 6 days before sectionizing. This holding time causes the fruit
to soften, making peeling and membrane separation easier dur-
ing sectionizing.

Whole fruit are subjected to a hot water treatment, prior
to peeling, commonly called hot peel process, for a specified length
of time: grapefruit 196 to 210F for 5 to 8 minutes and orange
196 to 210F for 4 minutes. This heat treatment softens the peel
of the fruit and facilitates peeling.
In recent years, a so-called double scalding process has been
developed which reduces the holding time of the fruit by 2 or
3 days. Fruit are passed through an enclosed slot-type drag
elevator and subjected to low pressure steam for a few seconds.
Just enough heat is applied to penetrate the peel. The fruit is
then conveyed to holding or curing bins. This process reduces
fruit rot and gives a less cooked flavor to the finished product
as scalding time can be reduced by 30%. However, when this
procedure is used more gentle handling of the fruit is required.

In commercial practice, fruit are peeled either by hand (5%)
or mechanical peelers (95%). Sometimes fruit may be peeled
without scalding, and this can only be accomplished by hand.
The cold peel process gives a superior flavored product (less
cooked flavor). Figure 20 shows a commercial peeler for grape-
fruit. It is important that the interval between peeling and lye
peeling be kept to a minimum, as it becomes harder to lye peel
the fruit with increased holding time between these two oper-

Lye Peeling
The main purpose for lye peeling (186) is to remove the
outer membrane of the sections from fruit that have been peeled.



Figure 20.-FMC Mechanical Peeler. (Courtesy FMC Corporation,

Baskets of peeled fruit are passed through a hot caustic spray
(190 to 212F), 1/2 to 2-1/2% solution of sodium hydroxide and
sodium carbonate, for 12 to 25 seconds; followed by 15 to 25
seconds without treatment to solubilize the albedo and section
membrane; and then passed through a 40 foot conveyor section
of water sprays to rinse the fruit. All lye solutions are collected
and recycled. Fruit solids gradually build-up in the alkali solu-
tion, so it is necessary to start each day with a fresh solution.
These waste lye solutions pose a considerable problem in the
treatment of waste effluents. The lye peeled fruit is then chilled
by one of the following methods: 1, water flooding; 2, spray
nozzles; or 3, counter current flow in trays at a temperature of
35 to 40F for 10 to 15 minutes. The cold water is recycled.
Chilling firms up the sections, makes them easier to sectionize,
and lessens off-flavor due to heat.

The peeled fruit is conveyed in baskets to the sectionizing
tables. The fruit is held by hand and placed on a revolving
spindle inserted in the core of the fruit. The segments are re-
moved with a special sectionizing-knife which is inserted be-
tween the fruit cells and membrane of each segment. Seeds are
removed from sections by brushing or tapping two segments
against each other. Approximately 50 to 60% of all grapefruit
sections are produced by this method.
There are two commercial types of mechanical sectionizers
used in Florida to sectionize fruit. One is produced by Brown
International Corporation, Covina, California and the other by
the FMC Corporation, Lakeland, Florida. Figure 21 shows a
Brown Sectionizer for grapefruit. A description of the FMC
citrus sectionizer (18) will be used to illustrate how fruit is
sectionized mechanically. Fruit is placed at approximately 30
per minute by hand into a cup on the feeder table. The operator
places the fruit blossom end up and centers the end under a
small beam of light. The blossom end is placed up because the
partitions between sections are more mature and are stronger
than at the stem end of the fruit. Precision centering devices
now accurately center the fruit, and a transfer assembly trans-
fers the fruit to a spindle with the center of the core precisely
aligned with the center of the spindle. The fruit is then carried
through 11 unit operations, supported externally by an inflated
latex cushion. A right and left hand path maker mechanism


Figure 21.-Brown Sectionizer for grapefruit. (Courtesy Brown Interna-
tional Corp., Covina, Calif.)

provides a path in the fruit in which probes can seek partitions
between sections. The fruit now moves through a six-blade head
station. The first three of these seek the partitions on the right
side of the sections, and the next three seek the partitions on
the left side of the sections. Each of these blade head stations
is provided with five blades. These blade head assemblies also
have probes which guide the blades to the partition. A highly
complex, mechanical system within the blade head assembly
permits a probe for each individual blade to independently seek
a partition. When the probes are aligned with the partitions,
they lock in place and move down through the fruit, separating
the sections from the partitions. The fruit next moves to a seed
shaker where probes are inserted into the seed area and vigor-
ously shake the sections back and forth to loosen the seeds and
separate the sections from the core. A spinner device, rotating
approximately 1-1/ revolutions, positively separates any re-
maining sections from the partitions or core and wraps the
partitions tightly about the spindle. The sections drop onto a
conveyor belt, where they are conveyed to a slotted vibrating


screen to remove the seeds and bits of fruit. The sections are
graded by hand and screened again to remove remaining seeds
and juice. At this point, they are inspected for final quality and
passed over a shaker screen to remove stray seeds and disperse
sections evenly over a filler belt.
The appearance of sections made mechanically is similar to
hand sections. A higher yield of sections is obtained mechanically
as hand sectionizers tend to cut out the seeds at the core of the
fruit, thus lowering yield. Fruit bits, juice, etc. are finished to
give 10 gallons of juice per hour per machine. This juice can
be processed into normal channels and eliminated from the
waste treatment plant.

Sections are filled into cans or glass containers by hand or
mechanical fillers. USDA Standards (181, 182) recommend that
each container be filled as full as practicable without impairment
to quality; but container fill as such is not a factor of quality.
Once the segments are filled into the container, they are covered
with a syrup or sweetened juice as follows: low density 12 to
160 Brix, medium density 16 to 180 Brix, and high density 18
to 35' Brix in compliance with Federal Standards. The container
is vacuum closed and hermetically sealed. Can size has an in-
fluence on the size of fruit used for sectionizing. For example,
size 70 and 80 grapefruit are normally filled into 8 ounce and
303 cans, while the larger sized grapefruit (size 54 and 64) are
reserved for 404 cans. The current industry trend is toward
a 26-ounce glass container as a standard size for segments.

Two types of sections are produced commercially. These are
chilled sections and canned or heat processed sections. Processing
data and methods for each process will be discussed individually,
as follows.

Chilled Sections
Segments directly from the sectionizer are filled into con-
tainers at room temperature, vacuum closed, and hermetically
sealed. They are then passed through a cooler (submerged water
bath or water sprays) at 35 to 40F to rapidly cool the product.
The containers are then blown with air to eliminate adhering
water, packed into containers, and placed in a cold warehouse


Table 26.-Boxes of grapefruit and oranges used in the production of segments and salads (173).

Boxes Fruit (1000 boxes)
Product 1973-74 1972-73 1971-72 1970-71 1969-70
Chilled grapefruit sections 466.7 510.0 444.7 463.4 468.1
Chilled orange sections 193.8 189.6 189.2 257.6 377.2
Chilled citrus salad 414.0 466.8 345.9 446.0 464.1
S Canned sweetened grapefruit sections 1,869.7 1,709.5 1,603.6 1,927.2 2,145.6
Canned dietetic grapefruit sections 310.0 231.7 171.9 293.7 227.8
Canned broken grapefruit sections 152.8 144.3 155.4 111.9 100.4
Canned citrus salad:
Oranges 48.7 53.3 92.9 77.4 101.8
Grapefruit 68.0 63.9 122.4 101.6 142.7
Canned orange sections 16.3 18.7 5.4 13.8 14.7
TOTAL 3,540.0 3,387.8 3,131.4 3,692.6 4,042.4

at 36 + 2F. When long conveyors are used, a small quantity of
dry ice is sprinkled into each package so that the product will
be delivered cool to the warehouse. Generally, less than 0.1%
benzoate of soda is used to help preserve chilled sections. The
optimum range is 0.04 to 0.05% but should never fall below
0.04%. In recent years, chilled sections in glass have become
more popular due to eye appeal. The boxes of fruit that have
been used to produce citrus sections and salads for the past 5
years is summarized in Table 26. It is evident from these data
that chilled orange sections and chilled salads have been pre-
ferred over the canned product. While the consumption of canned
sweetened grapefruit sections has been greater than chilled
grapefruit sections, the present trend is for chilled grapefruit
segments to increase at the expense of canned grapefruit seg-

Heat Processed Sections
Cooking is done in a water immersion bath at a temperature
of 185 to 190F. The size of the container dictates the holding
time which may vary from 20 to 45 minutes. The larger the
container the longer the time required for processing. Regardless
of container size, the center temperature should never fall below
146 to 175F. After cooking, the containers are put through a
refrigerated water bath (60 to 75F) and exit at a temperature
of 90 to 100F, with enough residual heat to dry the cans before

Once the product has been processed and placed into packages
it should be handled as gently as possible. It is customary to
let the finished product stand in storage for a period of 2 weeks
before shipping. This holding time permits the degrees Brix in
the syrup and the degrees Brix in the sections to reach equilib-
rium by osmosis.

Gelled Citrus Products
New gel type citrus products, citrus salad and dessert gels,
gel whips, gelled sauces, and edible gels for filling the center
cavity and sealing the cut surface of fresh pre-prepared ready-
to-serve grapefruit halves have recently been developed by
Moore et al (127) and Rouse and Moore (155).


All purpose gel blend formulations can be tailor-made for
any given product. Two examples are as follows:

Grapefruit Gelled
Salad Orange
Gel Sauce
Gel blend (Sea gel PCL-2)4 1.000% 1.000%
Sugar 10.309 21.799
Potassium chloride (if needed) 0.175 0.175
Water 39.865 48.728
Calcium chloride (anhyd.) 0.015 0.015
Grapefruit concentrate (60.85 OBrix) 8.480
Orange concentrate (60 OBrix) 28.220
Grapefruit sections 40.000 -
Citrus oil emulsion (12% oil w/w) 0.156 0.063
100.000% 100.000%

The above gel systems will withstand processing in the acidic
range of citrus juices and sections and remain stabilized with
little or no separation of the liquid (minimal syneresis) during
storage. Gel systems can be modified for special mouth-feel re-
quirements. The gels may be prepared from either whole, broken,
or crushed (broken into small particles) sections of grapefruit
and oranges. They may be gelled in either orange or grapefruit
juices. Grapefruit gels with added mint or lime flavor and green
food color are attractive and tasty. Individual servings can be
packed for cafeteria and restaurant use. Gelled sauces and salad
gels can be made as either a store shelf or chilled type product.
Gel formulations used for the salad and sauce products can
be used as an edible coating for pre-prepared ready-to-serve
fresh grapefruit halves (156). Cored grapefruit halves with the
resultant cavity filled (32) and the cut surface coated with a
grapefruit juice gel and then wrapped in polyethylene shrink
film have a storage life of 2 weeks at 40F. Other fruit combina-
tions such as diced mango-orange salad (154) can be prepared
utilizing these gels.

4 Sea Gel PCL-2 commercially available from Marine Colloids, Inc., Spring-
field, New Jersey.


Frozen Juice Sacs
Both washed and unwashed juice sacs can be frozen and
stored at -10F for use as a stock material in various types of
beverages and food products. Frozen juice sacs are normally
produced from orange, grapefruit, tangerine, lemon, and lime
and possess the natural flavor of these fruits. Two methods have
been used for freezing juice sacs. The more common procedure
is to place juice sacs directly from the juice finisher in poly-
ethylene lined 5-gallon cans which are then sealed and placed
in -10F storage. Containers larger than 5-gallons, especially
55-gallon drums, have proved to be unsatisfactory, since they
are slow to freeze at the core of the drum, and enzyme activity
causes the product to darken and go off-flavor.
In the other process, juice sacs are evenly distributed over
a moving belt and CO: horns fog dry ice directly onto the belt,
resulting in instant freezing of the product. The frozen juice
sacs are removed from the belt and packaged in 5-gallon square
cardboard cartons with polyethylene liners and stored at -10F.
It has been estimated by the authors that approximately 18,000
tons of frozen juice sacs were marketed during the 1974 proces-
sing season.

Dried Juice Sacs
Juice sacs account for about 10 to 20% of the total refuse
from citrus juice plants and are considered to be one of the
major contributors to air pollutants from citrus feed mill stack
gasses (100). The segregation and recovery of juice sacs which
may be dried and utilized in human foods could result in substan-
tial economic returns to the citrus processing industry with ac-
companying reduced air pollution.

Raw Material Preparation
Dried juice sacs may be produced from either unwashed or
washed juice sacs. Due to the presence of invert sugars, the
unwashed juice sacs tend to caramelize during drying, resulting
in a dark colored product. Special drying equipment is needed
for processing unwashed juice sacs and will be discussed under
the section on drying procedures.
Washed juice sacs can be obtained from fruit which has been
processed by either the Brown Reamer or FMC-In-Line Extrac-
tor. The juice sacs are passed through a conventional three or
four stage pulp wash system to remove sugar and soluble solids.


Table 27.-Typical yield of juice sacs from grapefruit and oranges.
Extractor Finisher Wt Wt Unwashed Juice Sacs/
Type Fruit Strainer-Tube Screen Whole Fruit Juice Sacs Box Fruit Whole Fruit Peel Refusea
Extractor Variety Opening (in) (in) (Ib)b ) (I). (Ib) (%) (%)
FMC-In-Line grapefruit 0.040 0.020 518 28.2 4.6 5.5 10.7
"FMC-ln-Line grapefruit 0.090 0.020 495 47.8 8.4 9.7 18.2
FMC-In-Line grapefruit 0.090 0.020 2123 170.9 6.8 8.1 15.6
Brown reamer orange 0.018 451 15.1 3.0 3.3 7.5
Brown reamer orange 0.018 453 20.0 4.0 4.5 10.0
SPeel refuse: 44 lb/85 Ib box grapefruit 40 lb/90 Ib box of oranges.

This washing operation is sufficient to prepare the juice sacs for
drying. The fruit solids which have been washed from the pulp
are concentrated in conventional temperature evaporators to a
concentration of 50 Brix, stored in 55-gallon drums, and sold
to the beverage and related industries.
A typical yield of juice sacs from grapefruit and oranges is
shown in Table 27. Data for recovery of juice sacs using FMC
equipment show that the manner in which juice is finished has
a direct bearing on the yield of juice sacs recovered from grape-
fruit. Processing variables, such as rpm, screen size, and back
pressure, with any given piece of finishing equipment have a
direct bearing on the yield of juice and juice sacs. Other factors
that may influence yield are fruit variety, fruit size, fruit ma-
turity, and growing season.
Drying Procedures
Foam-mat drying and freeze-drying are two methods which
have been used for drying unwashed juice sacs. In foam-mat
drying, a foaming agent is mixed with the juice sacs and
homogenized to produce a foam. Then the foam is evenly dis-
tributed over a moving stainless steel belt and dried to the
desired moisture content by hot air as the belt passes through
humidity controlled drying chambers. The end product is hygro-
scopic and must be removed from the belt in dehumidified rooms
and packed in suitable containers. Freeze-drying of juice sacs is
a vacuum-drying method in which the sacs are kept frozen
during dehydration. Juice sacs dried in this manner are of very
good quality but are relatively high in cost.
Washed juice sacs have been dried commercially with drum
dryers and triple pass indirect fired dryers. During drum drying,
washed juice sacs are applied to a steam-heated, stainless steel
roll or drum. The drum speed and temperature are regulated to
give a thin film of the desired moisture content. The triple pass
indirect fired dryers are conventional dryers used for the dehy-
dration of livestock feed and must be operated at product tem-
perature below 140F to give a satisfactory finished product.
The yield of dried unwashed juice sacs can vary from 0.3 to
1.4 pound/box of fruit depending on the finishing operation. A
typical material balance for processing and drying orange and
grapefruit juice sacs is shown in Table 28. Washed juice sacs
yield approximately 1/; that of unwashed sacs and range from
0.1 to 0.5 pound/box of fruit with a mean average yield of ap-
proximately 0.4 pound/box of fruit. A product having satisfac-


Table 28.--Typical processing data for dried washed juice sacs.
Fruit Variety
Process Variables
Orange Grapefruit
Unwashed juice sacs, Ib 211.5 170.9
Washed juice sacs, Ib 157.3 146.2
Dried juice sacs, Ib 10.2 10.1
% moisture dry juice sacs 4.5 9.0
Drying ratio: wet/dry 15.7/1 14.6/1
Drying rate: Ib/ft2/hr 0.20 to 0.24 0.20 to 0.24

tory appearance, storage stability, and reconstitutability can be
produced by dehydrating the washed juice sacs having 92 to
97% moisture to approximately 8 to 10% moisture.
Citrus juice sacs may also be dried with solvents such as
acetone. Using this procedure, the dried juice sacs are light and
fluffy and when reconstituted with water appear as individual
juice cells.

By proper milling techniques, the dried juice sacs can be
sized to any consistency desired by the customer. The more
common forms of dried juice sacs are grits, flakes, and flour.
Flakes have the appearance of oatmeal and are usually prepared
from drum dried sheets or films of juice sacs by grinding in a
Hobart mill to pass a -4 sieve (Tyler). Grits and flour are
manufactured by grinding dried flakes in a hammer mill. Grits
have the consistency of corn meal with a particle size range
between -16 to +30 mesh (Tyler); while the flour is ground
to pass a 100 mesh screen (Tyler).

Properties of Dried Juice Sacs
Dried juice sacs prepared from both oranges and grapefruit
have a very mild, bland flavor and aroma that in no way resem-
bles the fruit from which they are prepared. The color of dried
grapefruit juice sacs is white. Those prepared from oranges
have a characteristic orange color which is very unstable and
fades rapidly when exposed to light. Color, however, is not an
important factor for most uses of this product. When stored in
opaque containers, the color will disappear in 3 to 4 months and
become white, making it difficult to distinguish between juice
sacs from either oranges or grapefruit.


Table 29.-Physicochemical characteristics of dried washed juice sacs (100).
Fruit Variety
Orange Grapefruit

% Crude fiber 18.9 -
% Protein 9.0 -
% Pectin 20.6 -
% Ash 3.1 -
% Moisture 8-10 8-10
% Fat
Pet. ether 1.2-1.6 0.7-0.8
Acetone 1.7-2.1 -
Bulk density Ib/ft3 9.3 9.3
Water holding capacity 10/1 to 13/1 14/1 to 15/1
Fat holding capacity 4/1 to 5/1 4/1 to 5/1

Table 29 shows the physicochemical properties of dried
orange and grapefruit juice sacs. The fat content of dried grape-
fruit juice sacs is approximately 1/2 of that for oranges.

Antioxidant Treatment
Dried juice sacs develop rancidity that is characteristic of
the off-flavor that sometimes develops during storage of con-
centrated orange juices. This problem may be due to the break-
down and autoxidation of fatty acids and phospholipids in the
cellular tissue. The decomposition of the pigments may also con-
tribute to this flavor change.
It was found (100) that antioxidants could be added to the
juice sacs before drying to give a storage life of more than 1
year. Data showed that if juice sacs were not processed imme-
diately, they should be treated with an antioxidant before placing
in cold storage. It was found that when 600 ml of an antioxidant
solution containing 0.33 g of BHA and 3.3 g of TWEEN-80
(Atlas Chemicals Div., ICI American Inc.), is thoroughly mixed
and dispersed in 30 pounds of washed juice sacs, a dried product
with excellent keeping qualities results.
Sulfur dioxide gas and bisulfite treatments to destroy the
color of dried juice sacs has no beneficial effect. There is an
indication that S02 may give some improvement to the keeping
qualities of dried juice sacs, but there are not enough data to
make a valid judgement.


Handling and Storage
Dried juice sacs are normally filled into 55-gallon fiber-board
drums with polyethylene liners. Nitrogen pack is not necessary
but would be a good precautionary measure for prolonged stor-
age. The drums can be stored in a warehouse at ambient room
temperature with no apparent adverse effect. Precautionary
measures should be taken to prevent weevils in products that
are stored for more than 1 year.

Dried orange and grapefruit juice sacs have a potential use
in a variety of foods for human consumption. Such products
include meat products, breading mixes for dried foods, pie fill-
ings, economy fruit cakes, dehydrated beverage mixes, synthetic
juice products, beverage bases, canned gravies, sauces and pud-
dings, dehydrated pudding, sauce and gravy mixes, preserves,
cookie fillings, and pet foods. Because of their exceptional water
and fat absorptive properties, dried juice sacs could be used as
emulsifiers or binders. Since juice sacs are natural food products
rather than synthetic additives, they should prove to be valuable
food adjuncts for specialty food processors. Braddock and Kester-
son (29) have demonstrated that dried juice sacs can be colored
and flavored to resemble various products such as: grape, straw-
berry, blueberry, raspberry, chocolate, etc.

Citrus Purees
In the past, citrus purees were made from the whole macer-
ated fruit. Today, this practice no longer exists and purees are
generally prepared from concentrated citrus juice 60 to 650
Brix, juice sacs (heat stabilized), sugar, color if necessary, flavor
as specified, and citric acid to adjust pH. The most popular
citrus purees are orange, lime, lemon, and tangerine. For the
most part, purees are used as flavors for sherbets, bar mixes,
bakery products, etc. (168). Citrus sherbets by law must contain
a minimum of 2% juice by volume in the final product. Sherbet
bases are generally prepared as 50-fold concentrates.
The oil content of purees (0.030 to 0.035% on a reconstituted
basis) is normally 50 to 100% higher than that used in the pro-
duction of beverage bases. Citric acid is used to adjust pH, which
can vary from 2.2 to 3.5, but is more normally about 3.0. Color
is added if necessary, but is usually withheld until the time of
manufacture. In some products, the addition of sugar is also


withheld to give a more concentrated flavor and reduce shipping
costs. When pulp or juice sacs are used, they amount to no more
than 6 to 12.5%. Actually, this is about the same pulp content
as if a pulpy juice were used to prepare the concentrate.
As a rule, purees are frozen and maintained at a temperature
of -10F by the processor. Under these conditions, it is not
necessary to pasteurize the product. The flavor of the frozen
product, due to the high oil content, is far superior to a pasteur-
ized product. When shipped to the consumer, purees are main-
tained at a temperature of 35 to 40F and have a satisfactory
shelf-life of 3 to 4 months.
Purees are filled as cold as possible into the following con-
tainer sizes: 46 ounce cans, No. 10 cans, 4.5 gallon pails, or 55
gallon drums and hermetically sealed prior to freezing. The more
popular container sizes are No. 10 cans and 4.5 gallon pails.
When it becomes necessary to prepare a pasteurized product
for storage at ambient temperature, the puree is homogenized,
pasteurized at 180F for 17 seconds, and immediately cooled on
the regeneration side of the pasteurizer. Pasteurized purees may
not possess a fresh fruit flavor and are inferior in flavor to the
frozen product.

Beverage Bases and Popsicles
Beverage bases have been produced for many years by Florida
citrus processors. Orange has proved to be one of the most
popular drink flavors for beverage purposes. With the advent of
pulp wash solids, which are ideally suited for the manufacture
of beverages, the base for drinks has been expanded to include
such flavors as grape, cherry, strawberry, etc. These bases are
manufactured for: 1, carbonated fruit base drinks; 2, noncar-
bonated fruit base drinks; and 3, popsicles.

Carbonated Drinks
Juice used for the preparation of these drinks should be
pasteurized at 195 to 205F from 4 to 6 seconds to inactivate
pectic enzymes, thus stabilizing the juice cloud, giving a fruit-like
appearance to the final drink. The pasteurized juice is then con-
centrated under vacuum to 60 to 65' Brix. These concentrated
juices are mixed with the desired amount of sugar, citric or
malic acid, color, flavoring agent, salt, vitamin C, and benzoate
of soda, and homogenized to completely disperse the added oil.


The base is repasteurized at 180F for 17 seconds (160F if ben-
zoated) and then cooled in the same pasteurizer unit; heat stab-
ilized juice sacs may or may not be added at this point. The
product is filled into the appropriate container size (46 ounce
to 55 gallon drums) and hermetically sealed. Current practice is
to withhold the addition of sugar and water until the time of
manufacture of the finished drink. The small containers should
be stored cool at 55 to 60F or frozen at --10F to prevent brown-
ing and maintain good flavor. The 55 gallon drums are stored at
-10F. One gallon of these bases will produce from 20 to 100
gallons of a carbonated beverage. A 50-fold base is the more
commonly accepted concentration. Carbonated beverages nor-
mally contain less than 10% natural fruit solids and range from
3 to 7% in order to impart a satisfactory cloud and avoid exces-
sive sedimentation in the final carbonated drink.

Noncarbonated Drinks
Bases for noncarbonated drinks are prepared in accordance
with the procedure outlined for the carbonated drinks except
the natural fruit solids are usually higher. Citrus ades and drinks
can vary from 3 to 30% natural fruit solids; however, the cus-
tomary amount is 10%. The exact juice content of the drink
must be declared on the label. Table 30 shows typical formulas

Table 30.-Typical formulas for high juice content orange ade bases.
% Juice in Finished Drink
15% 20% 25% 30%
Orange concentrate 1.31 gal 1.75 gal 2.18 gal 2.62 gal
(9 650 Brix
MO Sugar" 21.45 Ib 18.30 Ib 15.23 Ib 12.09 Ib
m Citric acid'' 1.70 Ib 1.43 Ib 1.17 Ib 0.91 Ib
Salt 0.31 Ib 0.31 Ib 0.31 Ib 0.31 Ib
Vitamin C' 0.067 Ib 0.067 Ib 0.067 Ib 0.067 Ib
M Oil emulsion 60 cc 60 cc 60 cc 60 cc
o (10% by vol)
SBenzoate soda 0.05 Ib 0.05 Ib 0.05 Ib 0.05 Ib
< (0.1%)

1 5 gal 320 Be 53.50 Ib 53.50 lb 53.50b 53.50 Ib
cSu (59.10 Brix)
50 gal of water makes 60 gal of 11.9" Brix drink a 25/1 ratio
5.4 Ib sugar required to raise final drink 1 Brix.
b Citric acid in concentrate calculated as 0.085% per degree Brix.
c Vitamin C-added to give 180 mg/46 oz can.


for the preparation of high juice content ade bases. Ade bases
are customarily mixed with five parts of water to give a finished
beverage of about 10 to 120 Brix with a sugar to acid ratio of
20:1 to 30:1.

Popsicle bases are prepared in a fashion similar to the car-
bonated and noncarbonated bases except for the inclusion of
gelatin. A typical orange juice popsicle formula is as follows:

6 oz. 650 Brix orange concentrate
192 gm Crystalline sugar
1.5 gm Salt
7.0 gm Gelatin dissolved in 50 cc water
4 drops Food color
6 cc Oil emulsion (10% by vol.)

The above formula yields 12 ounces of popsicle base and when
mixed with 30 ounces of water gives 42 ounces of final product.
This formula makes fourteen 3-ounce 230 Brix popsicles.

Brined and Sulfited Peel
For an unknown number of years, curing and preserving
citrus peel with brine has been a well established practice in
other citrus growing regions of the world. In Florida, the practice
is quite limited and is used primarily to preserve the peel for
candying at a later date.
Fruit that are bright and free from scale, melanose, or wind
scarring are ideal for this purpose and preferably should be
reamed to a clean half-cup containing a minimum of rag. Ac-
cording to one source (186), these cups of peel are washed,
nested in 52-gallon fir barrels, and completely covered with a
10% salt solution. The brine solution is maintained at a 10%
salt content until the peel is cured, which is judged by appear-
ance. When peel is translucent but not mushy or mealy, it is
covered by a fresh 15% brine solution and is ready for storage.
Quite often, 500 to 600 ppm of sulfur dioxide is added to prevent
Currently, about 1,500 tons of diced peel are preserved an-
nually with sulfur dioxide for use in making candied peel. Diced
peel is filled into polyethylene lined steel drums, and a weighed
amount of sulfur dioxide is added directly to each drum to give


a final concentration of 1,000 to 1,200 ppm. Excellent preserva-
tion of the peel is obtained. The high concentration of sulfur
dioxide tends to bleach the peel, but this presents no problem,
since the peel is colored when candied.
Alternatively, citrus peel can be preserved for later candying
by tray-drying the half cups (or diced peel) at moderate tem-
peratures. Preliminary experience has shown that this type peel
reconstitutes well, candies without toughness, and avoids the
sulfur dioxide bleaching effect. The high drying costs are offset
by the cheaper storage.

Candied and Glycerated Citrus Peel
Candied citrus peel is made from either fresh or brined peel.
Fresh peel, free of blemishes, is sought. It must be cooked until
tender, changing the water to remove some of the bitterness
and a portion of the peel oil. At times, the peel is roughened to
help release excess peel oil. Brined peel is soaked in hot or cold
water, depending on the thickness, to remove the salt prior to
The tenderized peel from either process is drained, diced, and
immersed in a sugar syrup made from mixtures of sucrose and
dextrose. Sugar concentration is increased gradually to approx-
imately 500 Brix over many days to permit thorough penetration
of sugars. The partially candied peel is cooked finally with a
more concentrated sugar solution (76 Brix) to complete the
candying operation. Food colors are added during the candying
operation to impart pleasing colors to the product. The candied
peel is finally drained, dried, and dusted with powdered sugar or
corn starch. Candied peel is prepared sometimes by a so-called
"quick process." Tenderized peel is cooked in a low Brix sugar
syrup that penetrates the peel and increases in concentration by
evaporation. Cooking tenderized peel with a sugar syrup in a
vacuum allows it to be candied in 30 to 40 minutes. Breaking the
vacuum intermittently, during the cooking, prevents the forma-
tion of bubbles in the candied peel. The lower cooking tempera-
ture imparts a better color to the product. In Florida, it is
customary to produce red and green candied peel from grape-
fruit while candied orange peel is the natural color of the orange.
A so-called glycerated peel (176) can be prepared by using
a 60% glycerol and 40% corn syrup solution (these percentage
limits are important to produce a noncrystalline amorphous
product) in ratio of 3:1 or 4:1 of corn syrup-glycerol solution


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