• TABLE OF CONTENTS
HIDE
 Front Cover
 Preface
 Acknowledgement
 Table of Contents
 Introduction
 Review of literature
 Methods of commercial manufact...
 Experimental procedure
 Methods of analyses
 Oil of orange
 Oil of grapefruit and shaddock
 Oil of 'Persian' seedless lime
 Oil of lemon
 Mandarin type citrus oils
 Ultraviolet spectrum of citrus...
 Spectrophotofluorescence of citrus...
 Factors affecting the stability...
 D-limonene (citrus stripper...
 Peel oil content of various citrus...
 Citrus leaf and blossom oils
 Summary
 Literature cited
 Historic note






Group Title: Bulletin - Agricultural Experiment Stations, University of Florida ; 749 (technical)
Title: Florida citrus oils
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027438/00001
 Material Information
Title: Florida citrus oils
Series Title: Bulletin Agricultural Experiment Stations, University of Florida
Physical Description: 180 p. : illus. ; 23 cm.
Language: English
Creator: Kesterson, J. W
Hendrickson, Rudolph
Braddock, R. J ( Robert James )
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1971
 Subjects
Subject: Citrus oils   ( lcsh )
Citrus fruits -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 174-180.
Statement of Responsibility: by J. W. Kesterson, R. Hendrickson, and R. J. Braddock.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00027438
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000361138
oclc - 00698577
notis - ABZ9540
lccn - 72612730

Table of Contents
    Front Cover
        Front Cover
    Preface
        Page i
    Acknowledgement
        Page i
    Table of Contents
        Page 1
        Page 2
    Introduction
        Page 3
    Review of literature
        Page 3
        Page 4
        Page 5
    Methods of commercial manufacture
        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
    Experimental procedure
        Page 23
    Methods of analyses
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
    Oil of orange
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        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
    Oil of grapefruit and shaddock
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
    Oil of 'Persian' seedless lime
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
    Oil of lemon
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Page 103
    Mandarin type citrus oils
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
    Ultraviolet spectrum of citrus oils
        Page 114
        Page 115
        Page 116
        Page 117
        Page 118
        Page 119
        Page 120
    Spectrophotofluorescence of citrus oils
        Page 121
        Page 122
        Page 123
        Page 124
        Page 125
        Page 126
        Page 127
        Page 128
        Page 129
        Page 130
        Page 131
        Page 132
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
        Page 139
        Page 140
    Factors affecting the stability of citrus oil
        Page 141
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
        Page 147
        Page 148
        Page 149
        Page 150
        Page 151
        Page 152
        Page 153
    D-limonene (citrus stripper oil)
        Page 154
    Peel oil content of various citrus cultivars
        Page 155
        Page 156
    Citrus leaf and blossom oils
        Page 157
        Page 158
        Page 159
        Page 160
        Page 161
        Page 162
        Page 163
        Page 164
        Page 165
        Page 166
        Page 167
        Page 168
    Summary
        Page 169
        Page 170
        Page 171
        Page 172
        Page 173
    Literature cited
        Page 174
        Page 175
        Page 176
        Page 177
        Page 178
        Page 179
        Page 180
    Historic note
        Page 181
Full Text
Bulletin 749 (technical)


To Feed Mill


FLORIDA CITRUS OILS

J. W. Kesterson, R. Hendrickson, and R. J. Braddock






Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
J. W. Sites, Dean for Research


December 1971








PREFACE
The present writing is a revision of Technical Bulletin 521,
Essential Oils from Florida Citrus, by the authors. Information
presented in this bulletin has been obtained over a period of
24 years covering the span of development through a period
of phenomenal growth in the Florida citrus processing and
by-product industries.
Many advances in the technology of fruit processing and
subsequent production and processing of the citrus essential
oils have occurred, and much new analytical information has
been developed in recent years. However, all data herein are
basic and fundamental to the production of citrus essential
oils and are considered as applicable to this area of processing
in the present technology as in its early beginning. The authors
sincerely hope this revision will provide a comprehensive source
of knowledge in the production and processing of citrus oils.




ACKNOWLEDGEMENTS
This bulletin is dedicated to all segments of the Florida
Citrus Industry and especially to commercial processors whose
earnest cooperation for the past 24 years has made this contri-
bution possible.








PREFACE
The present writing is a revision of Technical Bulletin 521,
Essential Oils from Florida Citrus, by the authors. Information
presented in this bulletin has been obtained over a period of
24 years covering the span of development through a period
of phenomenal growth in the Florida citrus processing and
by-product industries.
Many advances in the technology of fruit processing and
subsequent production and processing of the citrus essential
oils have occurred, and much new analytical information has
been developed in recent years. However, all data herein are
basic and fundamental to the production of citrus essential
oils and are considered as applicable to this area of processing
in the present technology as in its early beginning. The authors
sincerely hope this revision will provide a comprehensive source
of knowledge in the production and processing of citrus oils.




ACKNOWLEDGEMENTS
This bulletin is dedicated to all segments of the Florida
Citrus Industry and especially to commercial processors whose
earnest cooperation for the past 24 years has made this contri-
bution possible.










CONTENTS


INTRODUCTION ......-- .. ------

REVIEW OF LITERATURE ............................

METHODS OF COMMERCIAL MANUFACTURE .......

Coldpressed Oils ....-- -----. .- .

Distilled Oils ... .... ----- ....

EXPERIMENTAL PROCEDURE ...................

Survey of Commercial Plants ..............--

Collection of Samples ---.......... ....

Experimental Samples ..........--- ...-

METHODS OF ANALYSES ............... --

Physical Constants of the 10% Distillate ............-.....

Optical Rotation .. ..........

Refractive Index ........... ........----

Specific Gravity ...........- .....

Aldehyde Determination .....- ......-

Evaporation Residue .....-- .........

OIL OF ORANGE .........--- -..... .....

Coldpressed Oil of Orange ........----.....................

Distilled Oils ...............-------

OIL OF GRAPEFRUIT AND 'SHADDOCK' .................

Coldpressed Oil of Grapefruit ..........-------

Distilled Oil of Grapefruit ............ .................

Coldpressed Oil of 'Shaddock' ................-.... .....

OIL OF 'PERSIAN' SEEDLESS LIME ................

Coldpressed Oil of Lime ----------------.

Distilled Oil of Lime ----- -............

OIL OF LEMON ........... ......... ..............

Coldpressed Oil of Lemon .......................................

MANDARIN TYPE CITRUS OILS ...............


Oil of Tangerine .........

Oil of 'Murcott' .....

Oil of Tangelo .........

Oil of 'Temple' Orange


Page

..-----...... ...-...-- 3

.....- .............. 3

....-...-...- .. 6

-------- 6

...................... 20

...............---... 23

..........-..- ..-.... 23

-.... ................... 23

................. .... 24

...................... 24

..-........-.....-....... 24

....-..-......-... ..... 24

....-..-.....~........ 25

...................... 26

..-...-...--.....-.... 27

....................... 28

................. ..... 29

............. ... 29

.-........- ...-..... ... 59

........................ 62

. ....---...-.. 62

................... 82

....---... .......... ... 83

----..----- ..- 83

.....-.............--- 87

..--.....----- 91

-.. ....--..- 94

....-...-.............. 95

.......-....-..-.....104


-.. ...... ..................................104

--. --- ----...---- .....105

--... ...................................- ...109

S..............-...-....... ..... 111








CONTENTS (Continued)
Page

ULTRAVIOLET SPECTRUM OF CITRUS OILS .............-..........---....114
U.S.P. Procedure -....- .......- ..--.................. 114
E.O.A. Procedure -......-..........---------------........115
Physicochemical Procedure to Determine Origin and
Method of Extraction ---------...-........ .............-----.117
Typical Ultraviolet Curves for Florida Citrus Oils ...................... ....121
Ultraviolet Absorption Spectrum of Florida Citrus Oils ..............--.....-121
SPECTROPHOTOFLUORESCENCE OF CITRUS OILS .......................121
Experimental Procedure ..............................------ 125
Methods of Analyses .....-........ ...........---- ------..126
Oil of Orange-------- .............-.. ....--- -...127
Oil of Grapefruit ..............------- ....-----------....129
Oil of Lemon ..-.. -----............. -------------- 133
Oil of Lime -...........--- ------.. ... .------ --... 139
FACTORS AFFECTING THE STABILITY OF CITRUS OILS ...........141
Evaluation of Citrus Oils ......---................. -........- 141
Antioxidants for Orange Oils ................ -.....- -----------149
Bacterial Degradation of Citrus Oils ...........---........-- .--------.....152
Autoxidation of D-limonene During Storage .......---......----........--------153
Storage and Handling of Citrus Oils -----.......--......---------------....154
D-LIMONENE (CITRUS STRIPPER OIL) --- ---......... --.... --..-----.--...154
Physical and Chemical Properties of D-limonene .......-..-..----.....-------154
Chemical Constants for D-limonene ...............................---155
PEEL OIL CONTENT OF VARIOUS CITRUS CULTIVARS ...........-155
Historical -.................-.----.......... ----- ---- 155
Quantity of Peel Oil in Various Citrus Cultivars --.......--..-.............------ 155
CITRUS LEAF AND BLOSSOM OILS .........--.............-......------ 157
Historical ....-.....-.... ... ---------.. ---.. 157
Compounds Identified in Citrus Leaf Oils ....-------..... -------.--.-160
Volatile Components from Citrus Flower Parts ..........- --..............-------- 161
Percentage Composition of Leaf Oils from Tangerine, Orange, and
Grapefruit for One Season ....... -------......-....... 168
SUMMARY ...... --..........- --------............. ..169
LITERATURE CITED ..... ------........------- -----..174








FLORIDA CITRUS OILS


J. W. Kesterson, R. Hendrickson, and R. J. Braddock'

INTRODUCTION
Today, the processing of citrus fruits is a vast and important
part of the Florida citrus economy. This industry has grown to
such proportions that approximately 92% of the Florida orange
and 66% of the grapefruit crop is now processed (Table 1).
The principal and primary products that result from the process-
ing of this huge quantity of fruit are canned single-strength
juices, frozen and hot pack concentrated citrus juices, and
canned citrus sections.
After the juice has been extracted, approximately 45%
of the weight of the citrus fruit remains as cannery refuse
consisting of peel, pulp, rag, and seeds (6.5 billion pounds).
During the past 25 years, an entirely new industry has developed
to utilize these enormous quantities of refuse from the canneries
which formerly were considered waste products, but which are
now fundamental in the economy of Florida's citrus industry.
The principal purpose of the investigations presented in this
publication was to determine by what means essential oils of
very high quality could be produced. Through the use of the
information obtained to date, it has been possible for the citrus
industry in Florida to produce citrus oils which consistently meet
the specifications of the United States Pharmacopoeia (106)2, as
well as other quality requirements of essential-oil consumers
throughout the country. Production of oils of highest quality
and uniformity has resulted in a larger consumer market.
Another purpose of the work was to determine the relationship
between the physical and chemical characteristics of the various
types of oils, and such factors as methods of extraction, methods
of processing, fruit variety, fruit maturity, etc.

REVIEW OF LITERATURE
Many investigators have pointed out that the quality of citrus
oils is dependent upon many factors. Some of these are soil,

1Professor (Chemist); former Associate Professor (Associate Chemist)
deceased; and Assistant Professor (Assistant Food Scientist); Agricul-
tural Research and Education Center, Lake Alfred, Florida 33850.
2Figures in parentheses refer to Literature Cited in the back of this
bulletin.








FLORIDA CITRUS OILS


J. W. Kesterson, R. Hendrickson, and R. J. Braddock'

INTRODUCTION
Today, the processing of citrus fruits is a vast and important
part of the Florida citrus economy. This industry has grown to
such proportions that approximately 92% of the Florida orange
and 66% of the grapefruit crop is now processed (Table 1).
The principal and primary products that result from the process-
ing of this huge quantity of fruit are canned single-strength
juices, frozen and hot pack concentrated citrus juices, and
canned citrus sections.
After the juice has been extracted, approximately 45%
of the weight of the citrus fruit remains as cannery refuse
consisting of peel, pulp, rag, and seeds (6.5 billion pounds).
During the past 25 years, an entirely new industry has developed
to utilize these enormous quantities of refuse from the canneries
which formerly were considered waste products, but which are
now fundamental in the economy of Florida's citrus industry.
The principal purpose of the investigations presented in this
publication was to determine by what means essential oils of
very high quality could be produced. Through the use of the
information obtained to date, it has been possible for the citrus
industry in Florida to produce citrus oils which consistently meet
the specifications of the United States Pharmacopoeia (106)2, as
well as other quality requirements of essential-oil consumers
throughout the country. Production of oils of highest quality
and uniformity has resulted in a larger consumer market.
Another purpose of the work was to determine the relationship
between the physical and chemical characteristics of the various
types of oils, and such factors as methods of extraction, methods
of processing, fruit variety, fruit maturity, etc.

REVIEW OF LITERATURE
Many investigators have pointed out that the quality of citrus
oils is dependent upon many factors. Some of these are soil,

1Professor (Chemist); former Associate Professor (Associate Chemist)
deceased; and Assistant Professor (Assistant Food Scientist); Agricul-
tural Research and Education Center, Lake Alfred, Florida 33850.
2Figures in parentheses refer to Literature Cited in the back of this
bulletin.








Table 1.-Number of boxes and per cent of Florida oranges and grape-
fruit utilized in processing channels (19)3.

Oranges Processed Grapefruit Processed
Season
easo 1,000 boxes % 1,000 boxes %

1965-1966 80,518 84 19,823 57
1966-1967 121,624 87 26,319 60
1967-1968 83,404 83 18,198 55
1968-1969 116,396 90 25,833 65
1969-1970 124,437 92 23,138 66


climate, method of extraction of the oil, weather, and maturity
of the fruit.
Citrus oils are contained in oval, balloon-shaped oil sacs or
vesicles located in the outer rind or flavedo of the fruit. Winton
and Winton (111) described the exact location of these oil sacs
in their discussion of the microscopic structure of the flavedo
of the orange. Hood (35) found a wide variation in the oil
yield of Florida oranges, reporting values of 0.11 to 0.58%
calculated on the weight of the whole fruit. He stated that the
oil content does not reach its maximum until the oranges are
fully mature, but is present in commercial quantities before the
fruit is ready for harvest. He also noted that a decrease in oil
content immediately follows a period of rainfall. Bartholomew
and Sinclair (8) studied the effect of age, size, and environment
on the relative amounts of oil in California oranges. Atkins,
Wiederhold, and Heid (3) reported the oil content of cull 'Per-
sian' limes to be 0.32% on a whole-fruit basis. Hendrickson
(32,34) has recently shown that the influence of maturity
brought about an increasing quantity of oil per unit of surface
area as well as per unit of fresh weight for Florida 'Valencia'
oranges. The yield of oil from various citrus cultivars has been
presented.
To secure the oil from the peel of citrus fruits, the oil sacs
must be punctured by either pressure or rasping. Methods of
oil extraction used in Florida were investigated by von Loe-
secke and Pulley (107). They showed that the method of ex-
traction had an effect upon the physical characteristics of the
oil. However, they did not find any relation between the time
of year and the physical characteristics. They reported that
there were no great differences in the properties of the oil from







different fruit varieties or from fruit produced in different
counties.
Atkins, Weiderhold, and Heid (3) extracted oil from cull
limes by using a screw press and a Pipkin (92) press. The
centrifuging of lime oil emulsions has been discussed by Moore,
Atkins, and Wiederhold (80). Guenther (30), in a series of
articles, has reviewed methods of oil extraction used in the
United States and in foreign countries. He stated that the
method of oil extraction and the amount of carrier water used
in a process affect the quality of the oil.
The physical and chemical characteristics of Florida orange,
grapefruit, tangerine, and lime oils have been reported by many
early investigators (3,206,2,27,29,87,88,107). Some of these
reported results are presented in Table 2, which also includes
values for oils from other sources as reported by Poore (93)
and Guenther (24,26). Foote and Gelpi (20) noted variations
in the properties of different lots of Floridian oil of orange.
They also suggested that producers should unite in the blending
and marketing of their oils in an effort to maintain the same
quality from year to year.
Nelson (87), Nelson and Mottern (85,88), and Markley,
Nelson, and Sherman (78) have carried out investigations rela-
tive to the chemical constituents of orange, grapefruit, and tan-
gerine oils produced in Florida.
Guenther (25) stated that Naves found that Guinea orange
oils extracted from fully matured fruit showed a higher spe-
cific gravity, refractive index, aldehyde content, and evapora-
tion residue, but a lower optical rotation, than oils pressed from
green fruit.
When oranges were kept in cold storage for periods longer
than 6 weeks previous to the extraction of the oil, de Villiers
(13) found an increase in the specific gravity, optical rotation,
iodine number, and saponification value, but a decrease in the
aldehyde content of the oil. Kesterson et al. (33,47,48,49,50,51,
54,57,58,59,60,66,67,68,69,89) have carried out studies relative
to the physicochemical and related properties of orange, grape-
fruit, tangerine, lemon, lime, 'Murcott,' and tangelo oils pro-
duced in Florida.
The deterioration of orange oil as well as the effects of anti-
oxidants have been investigated by Kesterson and McDuff (46)
and Kesterson and Hendrickson (52,53) as well as by Proctor
and Kenyon (45,94) and Flores and Morse (18).
Sale (96) developed an ultraviolet absorbance test that has








become a part of the U. S. Pharmacopoeia specifications as a
criterion of quality for orange and lemon oils. Recently, the
authors (69,71) have shown spectrophotofluorescence to be a
most effective tool for the characterization of oils from different
citrus cultivars.
In recent years with the development of gas chromatography,
many investigators (11,40,61,62,64,65,70,79,83,102) have done
extensive work to elucidate the chemical composition of citrus
oils. With this analytical tool, they have found more than 200
different chemical compounds in orange oil, but only 122 have
definitely been identified.
Fundamental information relative to all types of essential
oils produced throughout the world is found in Perry (91) and
in Gildemeister and Hoffman (22). In 1952, Guenther (23)
published six volumes at which time he brought the whole sub-
ject up-to-date. In this work, the authors have attempted to
bring together all of the information and technology that has
been developed and published relative to Florida citrus oils.

METHODS OF COMMERCIAL MANUFACTURE
Coldpressed Oils
General Processing Procedure.-Citrus peel oils have been
expressed in Florida by seven different 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 recent years,
the FMC in-line extractor has been used to produce approxi-
mately 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 been replacing some
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, this
is not true, but rather 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 very similar in most of the commercial
plants. The crude oil emulsion is put through a finisher with a
screen opening of 0.20 to 0.27 inch: 1)screw type, 2) paddle
type, or 3) shaker screen (20 to 80 mesh) to recover substan-








tially all of the oil emulsion present in the slurry. Excessive
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 (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 aque-
ous discharge effluent should not contain more than 0.1 to 0.25%
oil under optimum operating conditions, and the sludge ef-
fluent should be no higher than that of the feed emulsion and
should usually be considerably less.
The oil-rich emulsion is fed directly to a self-thinking type
centrifuge (16,000 to 18,000 rpm) without water addition.
The feed rate to the polisher should not exceed 1 to 1.5 gal-
lons 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 needed to help 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 lo-
cated 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 temperature ranging from -100 to +250 F. De-waxing is a
function of time vs temperature. For orange oil, 5 days at -10o F
is sufficient to de-wax the oil, while it may require up to 3
weeks at +250 F. Oils that contain greater quantities of wax
will require longer holding times. These tanks should have a
capacity preferably 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. Tail-
ings in the settling tank can either be filtered or centrifuged to
remove the wax.















Property
measured


Specific
gravity
(25C/25C)
Refractive
index
(20C)
Evaporation
residue

Optical
rotation
(25C)

10% Distillate
Optical
rotation
(25C)

Refractive
index
(20C)


Coldpressed
Orange


U.S.P. XVII
specifications
(106)

0.842
to
0.846
1.4720
to
1.4740

43 mg/3 ml

not less than
+94 and not
more than +99
in 100 mm tube
equal to original
oil or not more
than +2*
difference
not less than
.0005 and not
more than .0018
lower than
original oil


Table 2.-Properties of citrus oils as reported by early investigators.

Florida California
Coldpressed Coldpressed Other Florida
Orange Orange Coldpressed Oils


Source 1 Source 2 Valencia Navel Grapefruit Tange-
rine
(107) (20) (93) (93) (29) (29)


0.8434 0.8425 0.8440 0.8455 0.8563 0.845
(200C/20oC)

1.4726 1.4734 1.4735 1.4738 1.4758 1.4748


4.18 2.80 3.61 4.53 7 to 8 3.3


+96.49" +95.5" +97.78 +96.93 +93.28 +92.5
(20C) (200C) (20C)


+97.55" +97.5* +99.21 +98.71
(20C) (20C)


Distilled Oils


Cali-
fornia Flor
orange lin
(24) (2(

0.840
to 0.8(
0.842 (15
1.4717
to 1.4
1.4730

0.5 to 1

+98
to +43
+99.1


Lime

(26)


0.886
(15)C)

1.4855


13.0


+41.26


1.4719 1.4729 1.4723 1.4724


.20*


ida
e
6)


532
C)

759







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 as
compared to 385 pounds. 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 ac-
complished by displacement of the air with nitrogen or carbon
dioxide. The ideal storage temperature is 650 to 70 F. 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 finisher, desludger feed, aqueous effluent from desludger,
sludge effluent from desludger, oil-rich emulsion from desludger,
polisher feed, aqueous effluent from polisher, and sludge ef-
fluent from 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 noncorrosive. Fittings and lines should be of stainless
steel.
Pipkin Roll Method of Extraction.-A Pipkin roll (92) is
shown in Figure 1, and the flow and material balance sheet for
this process is given in Figure 2. 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 adjusted 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, thereby
keeping it out of contact with the peel and thus eliminating to,
some extent its absorption by the albedo of the fruit. The main
disadvantage of this process is extremely low yields of oil.
Screw Press Method of Extraction.-In this method, tap-
pered screws press the peel against a perforated screen, which
ruptures the oil cells, and the oil is washed away by the expul-
sion of surplus water from the press. This operation can be
carried out with the screws in either a vertical or horizontal










'A .


Figure 1.-Pipkin roll (photograph courtesy Essential Oil Producers, Inc.,
Dunedin, Florida).


position. Water may or may not be used in the pressing opera-
tion. In this process, 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. Figure 3 is a flow and material balance
sheet for the manufacture of coldpressed citrus peel oil by the
use of screw presses.










Fraser-Brace Excoriator.-Whole fruit is passed through a
corridor of carborundum rolls in this process, as shown in
Figure 4. As fruit passes through the excoriator, it is turned
over and over, and abrasive rolls rasp the flavedo from the
fruit. Water sprays are directed onto the fruit and rolls to
wash away the oil and grated peel. The oil and water emulsion


PIPKIN ROLL
FLOW AND MATERIAL BALANCE SHEET
COLD PRESSED CITRUS PEEL OIL MANUFACTURE


AQUEOUS PHASE 1.5 GAL./GAL OIL
YIELD 1.8 LB. OIL/TON PEEL
VARIETY LATE SEASON ORANGES


APRIL I,. 1O41


JAMES w. InSTN1ON
OMWEN RDUFFP


Figure 2.-Flow and material balance sheet for process using Pipkin roll.





















































SCREW PRESS
FLOW AND MATERIAL BALANCE SHEET
COLD PRESSED CITRUS PEEL OIL MANUFACTURE
AQUEOUS PHASE 190 GAL./GAL. OIL
YIELD 4,90 LB. OIL/TON PEEL
VARIETY MIDSEASON ORANGES
MAH as, |e4 JAMEs w, ust|raon
rrt. orer a et ourr

Figure 3.-Flow and material balance sheet for process using screw press.



is passed over a screen to remove the suspended solid particles.
Then it is transferred to settling- tanks, where it is held from
3 to 12 hours to effect complete settling and to allow the emul-
sion to rise to the top of the tank. The oil emulsion is decanted
and processed by conventional centrifugation procedures. The
machine is completely enclosed, and very little loss of oil occurs.


12








The capacity of this excoriator is small in terms of processing
and handling fruit. For example, one three-tunnel machine will
handle no more than 60 to 75 boxes of fruit per hour (90
pounds per box). This would necessitate a battery of graters
larger than the juice extraction plant which is not practical
for large operations.
Another disadvantage of the Fraser-Brace excoriator, as
well as all other rasping machines, is the high bacteriological
count of the juice extracted from fruit that has been grated.
The bacteriological count of orange juice is doubled; but in acid
fruits, the effect is not so pronounced. However, oil yields are
exceptionally good by this method. Figure 5 is a flow and ma-
terial balance sheet for this process.
FMC Rotary Juice Extractor.-The Food Machinery Cor-
poration rotary juice extractor (Figure 6) provides a method


CROSS SECTION 3-TUNNEL GRATER


Figure 4.--Cross-section diagram of Fraser-Brace excoriator (courtesy
Fraser-Brace Engineering Co., Tampa, Florida).















































FRASER eRACl ExTRACTOR PRESSED
FLOW AND MATERIAL BALANCE SHEET PEEL
COLD PRESSED CITRUS PEEL OIL MANUFACTURE OIL
AQUEOUS PHA t SE 100 AGAAL./AL OILo
YIELD 70 LI OL /TON PEEL
VARIETY MIDSEASON ORANGES
SPRAY NOZZLE$ I, S 4
EXTRAOTORS ,. T
STORAsE TANKS **,10., II 12,15
1A.IR I USTUSM ONF


Figure 5.-Flow and material balance sheet for process using Fraser-
Brace excoriator.


whereby both the juice and the peel oil from whole fruit are
secured simultaneously, but in such a manner that they do not
come in contact with each other to any great extent. This ma-
chine is of the rotary type and has 24 squeezing heads, which
are all actuated by a common cam. The extractor is furnished
complete with a feeder mechanism and a built-in electric power
unit. Whole fruit is fed into a squeezing cup where just enough
pressure is applied to remove all juice from the fruit and at the

14









same time rupture the oil cells. The juice and oil emulsion are
collected in separate trough assemblies. This machine has been
replaced by a more efficient counterpart called the FMC in-line
extractor. The flow and material balance sheet for this process
is given in Figure 7.
FMC In-Line Extractor.-The FMC in-line extractor (55)
was so named because the series of extraction cups are situated
in a straight line (Figure 8). This unit is used for oranges,
tangerines, lemons, limes, and grapefruit. The upper cups are
mounted on a common cross-bar which by means of a cam-drive
is moved in a fixed up and down path. The corresponding lower
cups are held in a rigid position. The sides of these cups con-
sist 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 hollow tube (or orifice tube) closely


Figure 6.-FMC rotary juice extractor (photograph courtesy FMC, Lake-
land, Florida).






































FMC Rotary Juice Extractor
Flow and Material Balance Sheet
Cold Pressed Citrus Peel Oil Manufacture


U UV3ML. Aqueos Phase= 12.5 Gal./Gal. Oil
Yield = 7.0 LB. Oil/Ton Peel
Variety =Midseason Oranges

JAMES W. KESTERSON
April 13, 1948 OMER R. M DUFF

Figure 7.-Flow and material balance sheet for process using FMC rotary
juice extractor.


fitted inside the strainer tube is caused to slide up and down
inside the cutter. The orifice tubes are fastened to a cross-bar
which is moved in a fixed up and down path by the same cam-
drive which moves the upper cups.
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 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. The inside of the
intermeshing cups is so contoured as to give virtually complete


Figure 8.-FMC in-line extractor (photograph courtesy FMC, Lakeland,
Florida).








support to the outer surface of 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, thus 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 car-
ries it to the by-product operation.
More recently, a new type of cup assembly has been devised
which makes it possible to recover the peel oil expressed during
the juice-extraction operation described above. This is desig-
nated as "oil cup assembly." In such a unit, 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 action,
it is collected on the baffles and directed to one side of the ex-
tractor. Considerable volatilization of the oil accompanies this
operation, as evidenced by the aroma of the surrounding at-
mosphere. 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 run
through a finisher equipped with a fine screen to give an oil
emulsion from which peel oil is separated by means of a centri-
fuge.
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 increased yields of 50% may be obtained by the addition
of sprays. The "mist spray" nozzles deliver from 3 to 6 gallons
of water per minute per extractor. Approximately 6 pounds
of water is absorbed by the peel from each 90-pound box of
oranges.
AMC Scarifier.-The American Machinery Corporation (Fig-
ure 9) method of releasing oil from the peel of citrus fruits by
the use of a scarifier is really only a refinement of the "Avena,"
"Speciale," and other rasping methods used in Italy and other
Mediterranean countries. The modern scarifier is designed for
continuous operation instead of the batch operation of those



























Figure 9.-AMC scarifier (photograph courtesy American Machinery Corp.,
Orlando, Florida).

earlier machines; and because it is placed in the processing
line, it lends itself to modern high-speed citrus installation.
In its design and manner of handling the fruit in a process-
ing line, the scarifier resembles the universally used transverse
brush washer. 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 stainless steel in such a 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 cylinders, 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 castings
to which they have been screwed. Each piece forms approxi-
mately one-quarter of the cylinder. They are so arranged that
they are self-cleaning of the raspings that might become lodged
inside the cylinder and thus promote efficient operation. The
punched holes are also of such size and spacing to prevent clog-
ging or filling up with peel while, at the same time, assuring
maximum piercing action.







The frame in which these rolls are mounted is inclined up-
ward 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
stabbed metal.
The entire interior of the enclosure contains a mist of water
provided by fog-type spray nozzles. This water serves to wash
the released oil from the surface of the fruit, to saturate the
flavedo with moisture and thus restrict the reabsorption of the
oil by the fruit, and to maintain a moisture-saturated atmos-
phere in the area above the fruit that discourages escape of
the oil through openings in the enclosure. 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 in a stain-
less steel pan beneath the machine for clarification and
processing.
Brown Peel Shaver.-The Brown peel shaver (Figure 10)
is a unique new means for extracting the oil from citrus peel.
Peel cups or quarters from juice extractors are fed into this
machine, which splits the peel into flat slices of albedo and
flavedo. The knife blade is wide, and 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 un-
der 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.
Since an easy adjustment of 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 flavenoids, mar-
malade strips, fillers, and many candied or pickled products.

Distilled Oils
Distilled Citrus Oils.-Distilled oil of orange, grapefruit, or
tangerine is secured by some processors as a by-product in the
canning of citrus fruit juices. Some of the citrus peel oil becomes
mixed with the juice as it is extracted by the various types of
juice extractors used in the canneries. Excessive amounts of
peel oil in the juices are detrimental to the quality of the canned
juice; therefore, in most canning plants the oil content of the













































Figure 10.-Schematic of Brown peel shaver (courtesy Brown Interna-
tional Corp., Covina, California).

juice is reduced to a desirable level by passing the juice through
a deoiler. The juice is usually flashed in the deoiler, which is
operated under a vacuum of 11 inches (1900 F) to 25.5 inches
(130 F), and a vapor mixture of oil and water is removed.
Then the mixture of oil and water vapor is condensed, and the
oil is separated from the condensate by decantation or centri-
fuging. Vacuum steam-distilled oils which are manufactured in
this manner have slightly different properties than oils which

21








are obtained by steam distillation at atmospheric pressure.
Essence Oils.-Essence oils are obtained from juice evap-
orators during the concentration of citrus juices. The principle
of essence (112) or volatile component recovery from citrus
juices is based on vaporization 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 and flavor-bearing aqueous com-
ponents. Concentration and removal of the essence and oil is
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 es-
sence and is decanted off. Figure 11 is a schematic for a single-
stage essence recovery system.
D-limonene.-D-limonene, or citrus stripper oil as it is more
commonly referred to by the Florida Citrus Industry, is obtained
as a by-product from the manufacture of citrus molasses.
Citrus press liquor contains from 0.15 to 0.50% peel oil and,
since this oil steam distills readily, some 60 to 80%o of the oil
present in the liquor can be recovered by flashing 240' F to
atmospheric conditions. The oil is recovered in Florentine-


Schematic-Single Stage
Essence Recovery
System


To Essence
Receiver


Figure 11.-Schematic for a single stage essence recovery system.









type separators from the condensate of the flash chamber and
multiple effect evaporators.

EXPERIMENTAL PROCEDURE
Survey of Commercial Plants
Information pertaining to the various processes used in
Florida for the manufacture of expressed and distilled citrus
peel oils was secured through the helpful cooperation of com-
mercial processors. In order to secure the data used in the
preparation of flow and material balance sheets, the authors
visited plants employing the various methods of oil extraction.
Rate of flow measurements were made on each unit process op-
eration for each individual process. Data were taken covering
periods of operation of 4 to 24 hours' duration. Information
obtained from each study was incorporated in a flow and ma-
terial balance diagram for that particular process, and these
are presented in Figures 2, 3, 5, and 7.

Collection of Samples
More than 800 samples of various types of coldpressed and
distilled citrus oils were secured from commercial processing
plants during the course of this study.
Seven-hundred and eleven samples of coldpressed oils of
orange, grapefruit, and tangerine were secured from seven
plants, each of which was using a different method for the
extraction of the oil from the peel. These samples were taken
from lots of oil ranging from 500 to 11,000 pounds, which
represented the production for approximately 1 week.
One plant furnished 12 samples of expressed orange oil,
which were analyzed to determine if storage of the fruit for
several days prior to the extraction of the oil would cause any
change in the physical and chemical characteristics of the oil.
Part of a selected lot of 'Valencia' oranges was processed
through the oil plant on the day it was picked, and an equal
quantity of the same lot of fruit was held in storage bins from
3 to 5 days before the oil was extracted. Each comparative
set of samples was made by the same type of extractor under
exactly the same conditions. These 12 samples were represen-
tative of the 132,000 pounds of oil extracted from approximately
840,000 boxes of fruit.
Samples of distilled oils of orange and grapefruit from 250 to
350-pound batches of oil were collected from five canneries, and
a total of 18 samples were secured.








Fifteen samples of 'Valencia' orange essence oil were ob-
tained from four different plants, each of which used different
processing equipment to recover the oil.

Experimental Samples
Experimental oil samples were prepared at the University
of Florida Citrus Experiment Station's pilot plant utilizing the
FMC in-line extractor with mist spray attachment and auxiliary
equipment previously described (55). Ten-box lots of fruit were
used to prepare oil samples from the orange-type cultivars,
while 15-box lots were used for the grapefruit cultivars.
The Fraser-Brace excoriator was used to prepare oil samples
from small immature fruit, since the immature fruit was not
suitable for processing in the FMC in-line extractor.

METHODS OF ANALYSES
The scientific examination of citrus oils is complex and di-
verse, so for the purpose of this bulletin, only the methods used
to determine those properties required as standards of purity
for the U. S. Pharmacopoeia (106) and Essential Oil Association
of the U.S.A. (15) will be given.

Physical Constants of the 10% Distillate (2)
Place 50 ml of the sample in a three-bulb Ladenburg flask
having main bulb 6 cm in diameter and of 120 ml capacity and
the condensing bulbs of following dimensions: 3.5 cm, 3 cm, and
2.5 cm. The distance from bottom of flask to opening of side
arm should be 20 cm. Distill the oil at a rate of 2 ml per minute
until 5 ml has been distilled. Determine refractive index and
rotation of the distillate as directed.

Optical Rotation (23)
Procedure.-Place the 100 mm polarimeter tube containing
the oil or liquid under examination in the trough of the instru-
ment between the polarizer and analyzer. Slowly turn the analy-
zer until both halves of the field, viewed through the telescope,
show equal intensities of illumination. At the proper setting,
a small rotation to the right or to the left will immediately
cause a pronounced inequality in the intensities of illumination
of the two halves of the field.
Determine the direction of rotation. If the analyzer was
turned counterclockwise from the zero position to obtain the








final reading, the rotation is levo (-); if clockwise, dextro (+).
After the direction of rotation has been established, care-
fully readjust the analyzer until equal illumination of the two
halves of the field is obtained. Adjust the eyepiece of the tele-
scope to give a clear, sharp line between the two halves of the
field. Determine the rotation by means of the protractor; read
the degrees directly, and the minutes with the aid of either of
the two fixed verniers; the movable magnifying glasses will
aid in obtaining greater accuracy. A second reading should be
taken; it should not differ by more than 5' from the previous
reading.
Temperature Correction.-No corrections for temperature
variations are made except in the case of citrus oils which con-
tain large amounts of highly active terpenes. The corrections to
be used, per degree centigrade, are:
Orange oil -- ..-- 13.2'
Lemon oil ...--.....- ..-- 8.2'
Grapefruit oil ...----... 13.2'
The proper correction is to be added if the reading is taken
at a temperature higher than the desired temperature and, con-
versely, to be subtracted if the temperature of the reading is
lower than the desired temperature.
All determinations should be carried out in a dark room.
Monochromatic sodium light should be employed. Some oils are
too dark in color for an accurate determination of the optical
rotation when a 100 mm tube is used. In such cases, a 50 mm
tube may be employed, or even a 25 mm tube, if necessary. Since
the rotation is reported for a 100 mm tube, any experimental
error will be multiplied by 2 for 50 mm tube, and by 4 for a
25 mm tube. Conversely, if a clear, light-colored oil is examined
which is only slightly optically active, the use of a longer tube
(200 mm) may often prove of advantage; the value to be re-
ported will be found by dividing the observed rotation by 2; any
experimental error will also be halved.

Refractive Index (23)
Procedure.-Refractometers offer a rapid and convenient
method for the determination of this physical constant. In our
work, we have used a Bausch and Lomb precision refractometer,
range 1.33 to 1.64, with most satisfactory results. A scale read-
ing (with illuminator) is obtained and converted to refractive
index by means of a conversion table. Refractive indexes are








reported at 200 C using a monochromatic sodium light source
,(5893-sodium yellow). Carefully clean the prisms with alcohol
and circulate water at 200 C. One or two drops of sample are
introduced through the tubulation on the upper side of the prism
case. Allow the instrument to stand for a few minutes before
the reading is made so that the sample and instrument will come
to equilibrium. When the proper illumination has been secured,
move the alidade backward and forward until a sharp dividing
line is obtained. Adjust this line so that it falls on the point
of intersection of the cross hairs. Read the scale by means of
a vernier and convert into refractive index.
After the material has been measured, the prism surfaces
should be carefully cleaned and dried so that no contaminating
material is carried over to subsequent measurements. Occasion-
ally, the instrument should be checked by means of a quartz
plate that accompanies it, or if such a plate is not available, by
means of distilled water at 200 C; the refractive index of pure
water at this temperature is 1.3330.
Temperature Correction.-All observations should be made at
200 C and the use of conversion factors is not recommended.
However, when it becomes necessary to make such corrections,
we have found the change in refractive index per degree for
Florida oils as follows:
Orange oil .....-...... 0.00045
Lemon oil ............ 0.00046
If the refractive index is reported at a temperature above
20 C, the proper correction must be added; conversely, if re-
ported at below 200 C, the correction must be subtracted.

Specific Gravity (23)
Procedure.-Fill the clean, dried pycnometer with the oil
previously cooled to a temperature below 250 C. Place the
pycnometer in a water bath and permit it to warm slowly to
25 C. Adjust the oil to the proper level, put the cap in place,
and wipe the pycnometer dry. Accurately weigh after 30
minutes.
The weight of the oil contained in the pycnometer divided
by the water equivalent gives the specific gravity of the oil at
250/250 (in air).
For a given pycnometer, the water equivalent need be deter-
mined only once; therefore, it is important that this determina-
tion be performed with great care and accuracy.








Temperature Correction.-Variations in specific gravity per
degree for Florida oils are as follows:


Orange oil .--
Lemon oil..


-. 0.00078
..- 0.00077


Aldehyde Determination
U.S.P. Procedure (106).-Pipet 50 ml of hydroxylamine hy-
drochloride T.S., previously adjusted with 0.5 N alcoholic potas-
sium hydroxide to a pH of about 3.4, into a conical flask
containing the specified amount of oil accurately weighed. Stop-
per the flask and allow to stand for 15 minutes at room
temperature, with occasional shaking. Titrate the liberated
hydrochloric acid with 0.5 N alcoholic potassium hydroxide to
a pH of about 3.4. Each ml of 0.5 N alcoholic potassium
hydroxide consumed in the titration is equivalent to:


1) Oil orange
2) Oil lemon


Oil orange
Oil lemon


% aldeh


78.13 mg aldehydes (decanal)
76.12 mg aldehydes (citral)

Sample size Reaction time Factor (f)
10 ml 15 min 0.07813
5 ml 15 min 0.07612

factor (f) x cc titr. x 100
ydew. s e i
wt. sample in gms


E.O.A. Procedure (15).-Triturate 0.1 gm of bromophenol
blue with 3 cc of twentieth-normal sodium hydroxide. When
solution is complete, dilute to 25 cc with distilled water. Dis-
solve 20 gm of hydroxylamine hydrochloride in 40 cc of dis-
tilled water, dilute to 400 cc with alcohol, add with stirring
300 cc of 0.5 N alcoholic potassium hydroxide and 2.5 cc of
the bromophenol blue solution, and filter the mixture.
ASSAY METHOD Add 75 cc of hydroxylamine solution
prepared as above to W gm (accurately weighed of substance


Oil grapefruit
Oil tangerine
Oil lime
Oil mandarin


Sample size Reaction time
(gm) (min.)
10.0 15
10.0 30
5.0 15
10.0 30


Factor (f)

0.07813
0.07813
0.07612
0.07813








to be tested) and mix thoroughly. Allow to stand at room
temperature for the time shown on the chart (previous page).
Titrate to the greenish-yellow end point of bromophenol blue
using 0.5 N hydrochloric acid. Perform a blank determination
using 75 cc of the hydroxylamine solution. Subtract the number
of cc of 0.5 N hydrochloric acid used in the titration of the
sample from the number of cc used in the blank.

N x .05 x 156.26
% decylaldehyde =
W
N x .05 x 152.23
%citral =
W
N = ml of 0.5 N KOH used in the titration
W = weight in grams of sample used
factor (f) x cc titr. x 100
% aldehyde
wt. sample in gms

The weight of sample W should be such that the cc of hydro-
chloric acid required for the titration of the flask containing
the sample is slightly more than half the cc required to titrate
the blank. This weight W given above is based on the use of
relatively fresh hydroxylamine solution which will give a blank
titration of over 30 cc of one-half normal hydrochloric acid.
The solution has a tendency to lose strength on standing more
than about 10 days.

Evaporation Residue
U.S.P. Procedure (106).-Evaporate 3.0 ml in a tared, 40 x
80 mm glass crystallizing dish on a steam bath for 5 hours.
Continue heating at 1050 C for 2 hours. Cool in a dessicator,
and weigh: Not less than 43 mg of residue remains.

Size sample Period heating Period heating
(steam bath) (oven at 1050 C)
Oil orange 3 ml 5 hr 2 hr

E.O.A. Procedure (15).-Place the quantity of sample speci-
fied in a tared 100 cc glass evaporating dish, previously heated
on a steam bath and cooled to room temperature in a dessicator,
and weigh it accurately. Heat the evaporating dish containing
the oil on a steam bath for the length of time specified. Allow







the dish and contents to cool to room temperature in a des-
sicator and weigh accurately. Determine the weight of the
residue and express as percentage of the oil originally taken.

Size sample Period of heating
(gms) (hrs)
Oil grapefruit 5 5
Oil tangerine 5 5
Oil lime 5 6
Oil mandarin 5 5
wt. of residue in gms x 100
% evaporation residue =---
wt. of sample in gms

Guenther Procedure (23).-Weigh accurately (to the closest
milligram) a well-cleaned Pyrex evaporating dish that has been
permitted to stand in a dessicator for 30 minutes. To this tared
dish, add the requisite amount of oil or solid (weighed to the
closest centigram) and heat on a steam bath for the prescribed
length of time. Then permit the evaporating dish to cool to
room temperature in the dessicator and weigh (to the closest
milligram). Calculate the non-volatile residue obtained, the
so-called "evaporation residue," and express as percentage of
the original oil.

Size samples Period of heating
Oil lemon 5 gms 41/2 hrs

Conventional Pyrex evaporation dishes, 80 mm in diameter and
45 mm deep, are recommended.

wt. of residue in gms x 100
% evaporation residue
wt. of sample in gms

OIL OF ORANGE
Coldpressed Oil of Orange
The physical and chemical properties of samples of cold-
pressed oil of orange, which were secured from four commercial
plants each month from October 1947 through May 1948, are
presented in Table 3. Each of the four plants used a different
method for expressing the oil. These data are also shown graph-
ically in Figures 12 to 17, inclusive.









Table 3.-The physical and chemical properties of coldpressed orange oils produced in Florida during the 1947-48 processing season.
Refrac-
Refrac- tive Optical Aide- Evapo-
Type Variety Specific tive Index Optical Rotation hyde Ester ration
of of Gravity Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Extractor Fruit* 25*C/25,C 7 20 Distillate ence 25 Distillate ence tent tent due
D D 20 D 25 % % %
D D
October 1947
FMC
Rotary 100% H 0.8433 1.4729 1.4714 0.0015 +97.57 +97.75 +0.18 1.17 0.44 2.52
50% H
Screw press 50% PB 0.8419 1.4723 1.4708 0.0015 +97.57 +97.75 +0.18 1.01 0.42 2.20
November 1947
FMC 25% H
Rotary 75% P&S 0.8433 1.4728 1.4715 0.0013 +97.01 +97.05 +0.04 1.31 0.38 2.59
50% H
Screw press 50% PB 0.8422 1.4724 1.4709 0.0015 +97.57 +97.60 +0.03 0.92 0.30 2.02
December 1947
FMC 10% H
Roy 50% P
Rotary 40% S 0.8426 1.4725 1.4712 0.0013 +97.01 +97.06 +0.05 1.63 0.33 2.18
50% H
Screw press 50% PB 0.8420 1.4723 1.4709 0.0014 +97.53 +97.60 +0.07 1.34 0.48 1.77
January 1948
Fraser Brace 50% P
50% S 0.8458 1.4733 1.4709 0.0024 +95.16 +97.12 + 1.96 1.08 1.45 4.81
FMC 60% S
Rotary 35% P
Rotary5% H 0.8426 1.4724 1.4709 0.0015 +96.81 +96.81 0.00 1.74 0.42 1.94
50% P
Screw press 50% S 0.8416 1.4721 1.4707 0.0014 +97.49 +97.52 +0.03 1.55 0.33 1.38





Fraser Brace 50% P
50% S 0.8453
FMC 50% P
Rotary 50% S 0.8430


February 1948

1.4734 1.4703 0.0031 +95.16 +97.12 +1.96

1.4724 1.4710 0.0014 +96.81 +97.37 +0.56


45% P
45% S
Screw press 10% V 0.8420 1.4723 1.4710 0.0013 +97.13 +97.54 +0.41 1.41 0.20 1.68
50% P
Pipkin roll 50% S 0.8424 1.4722 1.4709 0.0013 +97.76 +97.77 + 0.01 1.70 0.15 1.49
March 1948
Fraser Brace 50% P
50% S 0.8449 1.4734 1.4710 0.0024 +95.21 +96.96 +1.75 1.64 0.35 3.70
FMC
Rotary 100% V 0.8428 1.4723 1.4708 0.0015 +96.61 +96.96 +0.35 2.04 0.08 2.08
50% P
Screw press 50% P&S 0.8421 1.4719 1.4711 0.0008 +97.04 +97.24 +0.20 1.52 0.04 1.95

Pipkin roll 100% V 0.8420 1.4718 1.4708 0.0010 +97.34 +98.19 +0.85 1.98 0.34 1.07
April 1948
Fraser Brace
100% V 0.8441 1.4730 1.4713 0.0017 +96.10 +97.61 + 1.51 1.65 0.97 3.12
FMC
Rotary 100% V 0.8431 1.4725 1.4712 0.0013 +96.19 +97.21 +1.02 1.97 0.53 2.09

Screw press 100% V 0.8420 1.4722 1.4711 0.0011 +96.69 +97.25 +0.56 1.52 0.53 1.71

Pipkin roll 100% V 0.8423 1.4721 1.4711 0.0010 +97.16 +97.52 +0.36 2.02 0.39 1.31
May 1948
Fraser Brace
100% V 0.8455 1.4733 1.4713 0.0020 +95.66 +98.10 +2.44 1.45 1.50 3.99
FMC
Rotary 100% V 0.8431 1.4723 1.4710 0.0013 +96.66 +97.83 +1.17 1.77 0.91 2.36

Screw press 100% V 0.8426 1.4721 1.4712 0.0009 +97.59 +98.32 +0.73 1.38 0.95 2.11

Pipkin roll 100% V 0.8425 1.4719 1.4710 0.0009 +97.73 +98.19 +0.46 1.72 1.01 1.57
*H = Hamlin, PB = Parson Brown, P = Pineapple, S = Seedling, V = Valencia.


1.08 1.50 4.93

1.78 0.38 2.19








FMC Rotary Juice Extractor
A Screw Press
Pipkin Roll
o Fraser Brace Excoriator
0.8
.846 U.S.P XVII *
o 0.842
O4 TO *
^ 0.845 0.846 *
I-


a 0.844

u- *-*
u0.843 -
a. *---*
L)
0.842 ------

OCT NOV DEC JAN FEB MAR APR MAY
Figure 12.-Specific gravity of coldpressed orange oils extracted by four
different methods (1947-48 season).



FMC Rotary Juice Extractor
1.474
A Screw Press
Pipkin Roll
Fraser Brace Excoriator

oa

1473






1.472 ---- T- ---- ----
of
LI- TO
cr 1.4740




I.471 i
OCT NOV DEC JAN FEB MAR APR MAY
Figure 13.-Refractive index of coldpressed orange oils extracted by four
different methods (1947-48 season).










FMC Rotary Juice Extractor
A Screw Press
+990 Pipkin Roll ---------- ------
In Fraser Brace Excoriator

5 +980
z U U

+970 -A----


< +960 *


o *--*--- *
+o 950 U.S.P XVII
NOT LESS THAN
+940
NOT MORE THAN
+94 ....................................
+990
I I I I I
OCT NOV DEC JAN FEB MAR APR MAY
Figure 14.-Optical rotation of coldpressed orange oils extracted by four
different methods (1947-48 season).

Data from the various processing plants pertaining to the
yields of oil obtained by the different methods of extraction
are presented in Table 4 and Figures 2, 3, 5, and 7. Table 4
also shows the relationship between the yields of coldpressed
orange oils, which were obtained by the four methods of ex-
traction, and all of the physical and chemical properties of the
oils, except the aldehyde content. Data for all four of the
different methods of extraction are not available for the months
prior to February; therefore, they could not be used to secure
average values for comparison purposes. The data presented
are average values for the 3 months March, April, and May.
They also were obtained during those months when only the
'Valencia' variety of oranges was being processed. Figures
18, 19, and 20 present these results in graphic form.
The relationship between the aldehyde content of expressed
oil of orange and the quantity of aqueous phase which comes
in contact with the oil during processing can be seen in Table
5 and Figure 21. Here, also, the average values for the alde-
hyde content of samples of oil produced during March, April,
and May are used. The results secured for oils extracted during
















Table 4.-Relation of yield to the characteristics of Floridian oil of orange.

Optical Refractive
Yield Specific Evaporation Rotation Index Ester Method
Lb. Oil/Ton Peel Gravity Residue 25 20 Content of
25oC/250C % D D % Extraction

9.70 .8448 3.60 +95.66 1.4732 0.94 Fraser-Brace
FMC
7.00 .8430 2.18 +96.49 1.4724 0.51 Rotary
4.90 .8422 1.92 +97.11 1.4721 0.51 Screw press
1.85 .8423 1.32 +97.41 1.4719 0.58 Pipkin roll








- FMC Rotary Juice Extractor*
A Screw Press
* Pipkin Roll
* Fraser Brace Excoriator










N -OT IEI--- TA -- ------ -- ----
NOT LESS THAN -
43mg/3ml


OCT NOV DEC JAN FEB
Figure 15.-Evaporation residue of coldpressed
four different methods (1947-48 season).


MAR APR MAY
orange oils extracted by


FMC Rotary Juice Extractor
Screw Press
Pipkin Roll
Fraser Brace Excoriator


1.2 TO 2.5 %


4.0


w3.0
z
o
0


0
2.0


rn L-


OCT NOV DEC JAN FEB MAR APR MAY
Figure 16.-Aldehyde content of coldpressed orange oils extracted by four
different methods (1947-48 season).


I


I I I I








FMC Rotary Juice Extractor
1.5 A Screw Press *,
Pipkin Roll
Fraser Brace Excoriator


1-- 1.0- \
S
I-
z
0











OCT NOV DEC JAN FEB MAR APR MAY

Figure 17.-Ester content of coldpressed orange oils extracted by four
different methods (1947-48 season).



4.0

O SPECIFIC GRAVITY
( EVAPORATION RESIDUE *3.5
u .5- A5
tLd





0-0






















o I I A
OCT NOV DEC JAN FEB MAR APR MAY

























t 2 3 4 5 6 7 8 9 10
YIELD- LB. OIL/TON PEEL
Figure 18.-Relation of specific gravity and evaporation residue of cold-
Figure 17.-Ester content of compressed orange oils extracted by fouryield.
different methods (1947-48 season).



-4.0

0 SPECIFIC GRAVITY
EVAPORATION RESIDUE -3.5


) /-3.0'
&i W

8.845. 2.5lW


Z.844- 2.O0


S.843 -1.5


1 .842- 1.0
1 2 3 4 5 6 7 8 9 10
YIELD LB.OIL/TON PEEL
Figure 18.-Relation of specific gravity and evaporation residue of cold-
pressed orange oils to yield.








1.4741


0 OPTICAL ROTATION
REFRACTIVE INDEX +99*
on 0
cL473 +98*

x rI
95 -+97*




o u
1.472 1.+96 4*
L.



1 2 3 4 5 6 7 8 9 10
YIELD LB. OIL/TON PEEL
Figure 19.-Relation of refractive index and optical rotation of coldpressed
orange oils to yield.


January and February by the Fraser-Brace extractor were not
included in these average values, because a basic change was
made in this processing method after these samples of oil had
been obtained. Extremely large quantities of water were being
used with this extractor during January and February. In
March, the amount of water used was reduced to give 100 gal-
lons of an aqueous phase per gallon of oil produced and the oil
extracted in that month contained 52% more aldehyde than
the February sample.
The analyses of samples of expressed oil of orange, extracted
during March, April, May, and June from 'Valencia' oranges
by the Pipkin juice extractor, are given in Tables 6 and 7.
Values in Table 6 are for oil which was extracted from fruit
on the day it was harvested; the data in Table 7 refer to oil
extracted from fruit which was held in storage bins from 3 to
5 days prior to its extraction. The differences between the
average values of the properties of the oils immediately ex-
tracted and the oils extracted from the stored fruit are presented
in Table 8. Significant differences were found only in the
chemical properties of these oils.
The maximum and minimum values for the physical and
chemical properties of samples of coldpressed orange oil from
seven commercial plants are presented in Table 9.













I-
z
I-

ao

I-
0.
W



1 2 3 4 5 6 7 8 9 10
YIELD LB. OIL/ TON PEEL
Figure 20.-Relation of ester content of coldpressed orange oils to yield.


Relation of Yield to Properties and U.S.P. Specifications.-
The factor found to influence the physical and chemical properties
of coldpressed oil of orange to the greatest extent was the
yield of oil secured from the peel. As shown in Table 4 and
Figures 18 and 19, as the yield increased the values of the
specific gravity, evaporation residue, and refractive index also
increased, but the values of the optical rotation decreased. Thus,
the percentage of the total amount of oil in the peel that is
extracted determines the characteristics of the oil and, therefore,
its final quality. As the yield of oil is increased, more high-
boiling, high-molecular-weight constituents are evidently ex-
tracted; the presence of a higher percentage of these compounds
in the oil causes a reduction in the percentage of d-limonene,
resulting in lower optical rotation values, since d-limonene is
the most optically active component in the oil.
Yield of oil obtained by the various methods of processing
varied 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
possible for- them to process and still obtain the maximum
amount of oil recoverable from the peel. This being the case,
the plants are operated in such a manner as 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. By operating in this manner, they may secure very








low yields of oil, despite the fact that they are capable of ob-
taining much higher yields with the use of the same equipment.
The yields of oil using the Pipkin roll and screw press
methods of extraction, shown in Table 4, appear to be low when
compared to the yields obtained by the other methods of ex-
traction, but this is caused by the operation of the equipment
from an efficiency standpoint on an hourly rather than a yield
basis. Quality of the oil is influenced by the yield obtained,
which in turn is determined by operational procedure of the
equipment used and other processing techniques.
Analyses of expressed oils of orange indicate that oil pro-
duced by some manufacturing processes at certain times during
the season did not meet the U.S.P. (106) specifications because
yields were too low or too high. Only one method of extraction
yielded oil that consistently met requirements of the U.S.P.
throughout the season. However, it is apparent that if oil is
extracted in such manner that the yield falls within a certain
range, then it will meet U.S.P. specifications.
By using data obtained during this investigation, it is pos-
sible for any processor to produce an oil meeting U.S.P. spec-
ifications, provided he is willing to change his manufacturing
procedures. He may still use available equipment, operating it
in such manner that he will secure a yield of oil having proper-
ties which are indicative of good quality. Based upon the data
accumulated, it is estimated that a yield of 3.5 to 6.5 pounds
of oil per ton of peel from midseason oranges or the extraction
of 45 to 60% of the total amount of oil in the peel of any
variety of fruit of good maturity will result in a coldpressed
oil of orange that will meet the specifications of the United
States Pharmacopoeia (106).
It might also be added that oil extracted about the middle
of May from 'Valencia' oranges which had passed peak ma-
turity did not meet U.S.P. standards. The reason that this late-


Table 5.-Effect of quantity of aqueous phase on the aldehyde content
of Floridian oil of orange.
Aqueous Phase Aldehyde Content Method of
Gal./Gal. Oil % Extraction
12.5 1.93 FMC Rotary
21.5 1.91 Pipkin roll
100.0 1.58 Fraser-Brace
190.0 1.47 Screw press









season oil was of lower quality was that low yields of oil were
obtained with this type of fruit because the peel had become
soft and pliable, making the extraction of the oil more difficult.
Effect of Aqueous Phase on Aldehyde Content.-The flavor
quality of oil of orange is dependent upon the many constitu-
ents of which it is composed. The aldehyde content of the oil is
indicative of the flavoring qualities of the oil, although other
constituents are also very important from a flavor standpoint.
Data in Table 5 and Figure 21 indicate that the aldehyde
content decreases as the amount of aqueous phase which comes
in contact with the oil during processing is increased.
The average aldehyde content of the expressed oils of orange,
secured during March, April, and May from the four plants at
which material balance studies were made, varied from 1.47 to
1.93%. In one plant-where, at the suggestion of the authors,
the water used in the process was reduced from extremely
large quantities to an amount sufficient to give 100 gallons
of aqueous phase per gallon of oil produced, while other vari-
able factors were kept constant-the aldehyde content increased
from 1.08 to 1.64%, or 52%. Thus, it is evident that to produce
an orange oil of high aldehyde content, the amount of aqueous
phase allowed to come in contact with the oil during processing





2.0

z
.---
z
0









0 50 100 150 200
AQUEOUS PHASE= GAL./GAL. OIL
Figure 21.-Influence of the quantity of aqueous phase which comes in
contact with the oil during processing on the aldehyde content of coldpressed
orange oils.
-I









orange oils.








should be reduced to as small a quantity as is practical under
operating conditions.
Recent work (68) has shown that as the quantity of aqueous
phase is increased, the amount of insoluble solids increases.
These insoluble solids, primarily pulp particles, presumably act
as ion-exchange resins and selectively 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. In addition to the above
there remains the possibility of enzymatic degradation.
Relation of Fruit Cultivar to Properties.-Consideration of
Table 3 and Figures 12, 13, and 14 shows that the oils manufac-
tured by any one process fell within a particular category of
their own and remained there throughout the season. The dif-
ferences in the physical properties of expressed orange oils ob-
tained from different varieties of fruit by any particular process
were not significant-except in the case of the Fraser-Brace
method of extraction where, during the month of April, an ap-
parently erratic variation occurred.
The aldehyde content of coldpressed oils of orange, as can
be seen from Table 3 and Figure 16, was highest when made
from 'Valencia' oranges. Mixtures of 'Pineapple' and seedling
oranges gave an oil with a lower aldehyde content, and mix-
tures of 'Hamlin' and 'Parson Brown' varieties yielded the
lowest aldehyde content oil.
Variety of fruit apparently had very little effect on the ester
content of the orange oils. Oil of orange produced by the Fraser-
Brace excoriator from midseason varieties that were partially
green in color was considerably higher in ester content than that
made by the same process later in the season from the same
varieties when they were completely orange in color, and it was
also higher in esters than oils produced by the other methods.
High evaporation residue values also were found for the oils
produced by the Fraser-Brace excoriator.
Storage of Fruit Prior to Oil Extraction.-Results obtained
indicate that the length of time fruit was stored prior to the
extraction of the oil was another factor which influenced the
characteristics and quality of the oil. This is illustrated by data
presented in Tables 6, 7, and 8, which show the effect storage
of the fruit had upon the physical and chemical properties of
the oil.
There were no significant differences in the physical prop-
erties of coldpressed oils of orange extracted from fruit on the








Table 6.-Properties of oil of orange expressed from fruit on the day harvested.

Refrac-
Refrac- tive Optical Aide- Evapo-
Quantity Variety Specific tive Index Optical Rotation hyde Ester ration
Date of Oil of Gravity Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Sampled Fruit 25*C/25C 20 Distillate ence a 25 Distillate ence tent tent due
Lbs. D 20 D 25 %
D D

3-22-48 11,000* Valencia 0.8428 1.4723 1.4708 .0015 +96.61 +96.96 +0.35 2.04 0.08 2.08
4-8-48 11,000 Valencia 0.8427 1.4725 1.4714 .0011 +96.38 +97.44 +1.06 1.94 0.53 2.07
4-14-48 11,000 Valencia 0.8431 1.4725 1.4712 .0013 +96.19 +97.21 +1.02 1.97 0.53 2.09
5-10-48 11,000 Valencia 0.8427 1.4722 1.4712 .0010 +97.26 +97.76 +0.50 1.84 0.71 1.85
6-1-48 11,000 Valencia 0.8428 1.4719 1.4707 .0012 +97.29 +97.77 +0.48 1.65 0.60 1.98
6-21-48 11,000 Valencia 0.8427 1.4719 1.4709 .0010 +96.97 +98.37 +1.40 1.45 0.45 1.74
Average 0.8428 1.4722 1.4710 .0012 +96.78 +97.58 +0.80 1.82 0.48 1.97
Each 11,000 pounds of oil represents approximately 70,000 boxes of fruit.








Table 7.-Properties of oil of orange expressed from fruit stored in fruit bins for three to five days.

Refrac-
Refrac- tive Optical Aide- Evapo-
Quantity Variety Specific tive Index Optical Rotation hyde Ester ration
Date of Oil of Gravity Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Sampled Fruit 25C/25C 7 20 Distillate ence 25 Distillate ence tent tent due
Lbs. D 20 D 25 % % %
D D
3-19-48 11,000* Valencia 0.8430 1.4723 1.4708 .0015 +96.61 +96.96 +0.35 1.92 0.25 2.07
4-10-48 11,000 Valencia 0.8426 1.4725 1.4710 .0015 +96.39 +97.23 +0.84 1.89 0.60 2.17
4-14-48 11,000 Valencia 0.8432 1.4723 1.4709 .0014 +96.52 +97.20 +0.68 1.89 0.63 2.33
5-10-48 11,000 Valencia 0.8421 1.4722 1.4711 .0011 +96.78 +97.50 +0.72 1.76 0.86 2.18
6-1-48 11,000 Valencia 0.8428 1.4720 1.4709 .0011 +96.89 +98.17 +1.28 1.59 0.77 2.14
6-21-48 11,000 Valencia 0.8426 1.4719 1.4708 .0011 +97.29 +98.37 +1.08 1.40 0.68 2.09
Average 0.8427 1.4722 1.4709 .0013 +96.74 +97.57 +0.83 1.74 0.63 2.16
*Each 11,000 pounds of oil represents approximately 70,000 boxes of fruit.








Table 8.-Influence of storage of fruit, prior to extraction, on the properties of coldpressed oil of orange.
Oil Expressed Oil Expressed
from Fruit Soon from Fruit %
Property After Harvesting After Storage Difference Difference
(Table 6) (Table 7)

Specific gravity 25C/250C 0.8428 0.8427 0.0001 Not significant
Refractive index 7t 20 1.4722 1.4722 0.0000 Not significant
D
Refractive index 10% distillate 20 1.4710 1.4709 0.0001 Not significant

Difference 0.0012 0.0013 0.0001 Not significant

Optical rotation a 25 +96.78 +96.74 +0.04 Not significant
D
Optical rotation 10% distillate a 25 +97.58 +97.57 +0.01 Not significant

Difference 0.80 0.83 0.03 Not significant

Aldehyde content, % 1.82 1.74 0.08 4.6

Ester content, % 0.48 0.63 0.15 31.3

Evaporation residue, % 1.97 2.16 0.19 9.6









same day it was harvested and those extracted from fruit that
was stored in fruit bins for 3 to 5 days before the oils were
extracted. However, significant differences were found in the
chemical properties. The ester content of the oil from stored
fruit was 31.3% higher than that extracted 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.-In the studies of the effect
of fruit storage on oil quality, all samples of oil of orange were
from the same variety of fruit and were extracted by the same
process. Therefore, over a period of 4 months information was
obtained in reference to the effect of maturity on the properties
of the oil. Here, again, differences were noted in the chemical
characteristics 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 gradually increased as the fruit became more ma-
ture. '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 Properties.-Maximum and
minimum values for the properties of coldpressed orange oil
produced in Florida by seven different processes over a period
of 23 years are shown in Table 9.
The 1947-48 fruit season was considered to be a very wet
year; whereas, the 1948-49 fruit season was considered to be
a very dry year. It would be expected that yearly variations
of this kind would result in differences in the physical and
chemical characteristics of the oil. However, only two factors
were affected to any extent. These were refractive index and
aldehyde content. The values for refractive index shown in
Table 10 averaged 0.0008 of a unit higher during the 1948-49
fruit season. Refractive index values for one process obtaining
high yields of oil exceeded the U.S.P. standards due to this
increase; whereas, the values for two processes obtaining low
yields of oil met the U.S.P. requirements due to this increase.
In Table 10, a correlation is shown between ester content and
yield of oil secured from the peel for the 1948-49 season. As








Table 9.-Maximum and minimum values for the properties of coldpressed orange oil produced by various methods.

Method of AMC Brown
Extraction ..... Pipkin Roll Screw Press Fraser-Brace FMC Rotary FMC In-Line Scarifier Shaver
No. of Samples 21 123 52 112 237 2 4
Yield, 0.75 to 1.0 3.5 to 5.0 4.5 to 7.5 2.0 to 3.0 3.0 to 4.5 3.0 to 5.0 3.5 to 6.0
Ibs. oil/ton fruit
Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min.


Property
Sp. gray.
25 C/250 C 0.8432 0.8420

Ref. ind. r 20 1.4734 1.4718

Ref. ind. 10%
20 1.4722 1.4708
dist. 77 D

Difference 0.0013 0.0007

Opt. rot. a25 +98.05 +96.64

Opt. rot. 10%
dist. a 25 +98.31 +97.30
D
Difference +1.28 +0.01
.Aldehyde 2.02 1.63
content, %
Ester content, % 1.01 0.15
Evaporation 2.42 1.07
residue, %


0.8426

1.4733


0.8416

1.4719


0.8458

1.4743


0.8441

1.4730


0.8443

1.4737


0.8420

1.4722


0.8438

1.4731


0.8424

1.4725


0.8449

1.4731


0.8433

1.4728


0.8435

1.4730


0.8427

1.4730


1.4723 1.4707 1.4724 1.4703 1.4727 1.4707 1.4717 1.4715 1.4716 1.4716 1.4723 1.4719


0.0015

+97.80


0.0007

+96.53


0.0031

+96.30


0.0016

+94.54


0.0015

+97.57


0.0010

+94.98


0.0014

+97.08


0.0010

+95.32


0.0015

+96.70


0.0012

+96.36


0.0011

+97.32


0.0007

+97.18


+98.65 +97.24 +98.70 +96.96 +98.73 +96.49 +97.92 +95.74 +98.16 +97.47 +99.11 +98.09


+1.41

1.85

1.09

2.23


+0.03

0.92

0.04

1.37


+3.70

1.65

1.63

4.93


+1.51

0.93

0.35

3.12


+2.00

2.04

1.34

3.22


+0.00

1.17

0.08

1.85


+1.51

1.96


+0.11

1.54


+1.80

1.86


+0.77

1.86


+1.89

1.66


+0.80

0.86


3.08 2.45 4.00 2.80 2.56 2.17
















Table 1O.-Relation of yield to the characteristics of coldpressed orange oil produced in Florida during the 1947-48 and
1948-49 seasons.

Specific Evaporation Optical Refractive Ester
Yield Gravity Residue Rotation Index Content Method
Lb. Oil/Ton 25C/25C % 25 7 20 % of
Peel D D Extraction
1947-48 1948-49 1947-48 1948-49 1947-48 1948-49 1947-48 1948-49 1947-48 1948-49
9.70 0.8448 0.8448 3.60 4.04 +95.66 +95.05 1.4732 1.4739 0.94 1.08 Fraser-Brace
7.00 0.8430 0.8431 2.18 2.46 +96.49 +96.16 1.4724 1.4732 0.51 0.77 FMC Rotary
4.90 0.8422 0.8421 1.92 1.75 +97.11 +97.07 1.4721 1.4729 0.51 0.64 Screw Press
1.85 0.8423 0.8423 1.32 2.06 +97.41 +97.51 1.4719 1.4727 0.58 0.49 Pipkin Roll








yield increased, the values for ester content increased. This
correlation was not evident during the 1947-48 season.
As shown in Table 11, average values for aldehyde content
of oils produced during the 1947-48 and 1948-49 fruit seasons
were 1.73 and 1.49 percent, respectively. The difference between
these two values shows a decrease of 16.1% in the aldehyde
content of oil produced during the 1948-49 fruit season. Ap-
parently, dry weather had some physiological effect on the fruit
which caused the aldehyde content of the oil to be lower.
Data presented in Tables 10 and 11 represent average values
for the months of March, April, and May, during which time
most of the oranges processed were 'Valencia.'

Table 11.-Aldehyde content of coldpressed orange oil produced in Florida
during the 1947-48 and 1948-49 seasons.
Aldehyde Content Method
%_ of
1947-48 1948-49 Extraction
1.93 1.60 FMC Rotary
1.91 1.66 Pipkin roll
1.58 1.23 Fraser-Brace
1.47 1.46 Screw press
1.73 1.49 All methods (average)


Aldehyde Content vs Rainfall.-The aldehyde content of ex-
pressed orange oil will vary considerably from one season to
another. Low aldehyde content oils are generally considered
to be inferior to oils with a high aldehyde content from the
standpoint of flavor and aroma. For this reason, it would be
desirable to always produce an oil with a high aldehyde content.
However, this has not been possible since the factors respon-
sible for this phenomenon have not been fully understood. Data
collected for a period of 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 aldehyde
content will be for any given season.
The aldehyde content of 'Valencia' orange oil shows a posi-
tive correlation with the total rainfall (Table 12), with a cor-
relation co-efficient of 0.603 which is significant at the 5% level.
These data are presented graphically in Figure 22. The aldehyde
content of the oil rose with increased rainfall and diminished
when rainfall decreased. The 1954-55 and 1964-65 seasons are







90-A A RAINFALL 1.8
Cn / \ --%ALDEHYDE



E 70 / 1.6 0


60 -1.5 m

50- -1.4


40 1.3



51-52 55-56 59-60 63-64
SEASON
Figure 22.-The aldehyde content of 'Valencia' orange oil as related to
total rainfall.

exceptions to this rule. This may possibly 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 relationship. The interrelationship of the per-
cent aldehyde content and total rainfall is shown by the re-
gression line in Figure 23. If the rainfall for a particular
season is known, it is an easy matter to look at this chart and
predict in advance oil quality for any given season.
The aldehyde content could possibly be maintained at a
satisfactory level by the proper use of irrigation water. Future
widespread use of irrigation will undoubtedly result in an im-
provement in the overall quality of Florida orange oil.
Budwood and Rootstock as Related to Oil Yield and Quality.-
A comparison (32) of peel oil content (Table 13) from 34 dif-
ferent 'Valencia' budwood selections on a common rootstock
is shown. Peel oil content ranged from 11.1 to 15.7 pounds per
ton of fruit. Differences in yield were found to be statistically
significant. These data suggest that the peel oil yield can be
increased approximately 4.6 pounds per ton of fruit by proper
choice of budwood selection; but, not enough information has
been collected to recommend the ideal selection.
been collected to recommend the ideal selection.









Table 12.-Aldehyde content of Valencia orange oil as
rainfall.


related to total


Season Total Aldehyde Number of
Rainfall* Content* Oil
March May Inches % Samples

51 52 73.65 1.61 8
52 53 68.28 1.61 8
53 54 63.53 1.62 8
54 55 48.10 1.71 18
55 56 43.64 1.41 11
56 57 73.12 1.72 8
57 58 72.13 1.71 8
58 59 72.10 1.80 9
59 60 90.73 1.74 27
60 61 77.25 1.60 8
61 62 45.64 1.55 12
62 63 54.95 1.49 12
63 64 62.91 1.62 8
64 65 49.17 1.67 7
Correlation Coeff. = 0.603 (Significant at 5% level).


* 0


Y =0.00416X+1.36

t = 2.600(n= 14)


1.4 I I I I
40 50 60 70 80 90 100

RAINFALL (15mo) Inches (X)
Figure 23.-Regression line to show the interrelationship of percent
aldehyde content and total rainfall.




Table 13.-Variations in peel oil content of fruit from trees of different budwood selections having a common rootstock.
16-Fruit Sample* Peel Oil*
Fruit Mean Mean ml peel % in Lbs/ Lbs/ton Lbs/
Seedling Yield fruit surface oil/ whole fruit tree fruit acre**
No. Selections Avgt wt (g) area (cm2) 100 cm2
1. VS-1-18-31 1.6 204.8 160.3 0.900 0.62 0.89 12.4 78
2. VS-1-14-1 1.6 208.7 165.5 0.992 0.69 0.99 13.8 86
7. VS-26-1-1 1.5 244.8 183.3 0.908 0.60 0.81 12.0 70
25. VS-1-12-1 1.4 210.4 165.0 0.906 0.62 0.79 12.6 69
26. VS-1-12-5 1.7 223.0 171.6 0.874 0.59 0.90 11.8 78
27. VS-1-16-2 1.7 221.0 169.9 0.907 0.61 0.94 12.2 82
28. VS-1-21-30 1.9 204.6 159.7 0.860 0.58 1.01 11.8 87
29. VS-1-18-3 1.7 189.1 150.8 0.933 0.65 1.00 13.1 87
30. VS-1-19-42 1.7 204.1 160.6 0.920 0.64 0.97 12.7 85
31. VS-1-14-32 1.3 274.4 197.8 1.11 0.70 0.82 14.1 71
Old-line selections
3. V-5-6-1 1.3 172.3 142.7 0.879 0.64 0.74 12.7 64
4. V-10-12-7 1.8 174.8 143.2 0.840 0.60 0.98 12.1 85
5. V-16-6-22 1.4 181.6 148.6 0.848 0.61 0.76 12.1 66
6. V-16-14-22 1.8 143.9 126.0 1.023 0.78 1.27 15.7 111
8. V-29-1-12 1.5 175.1 143.6 0.859 0.67 0.90 13.3 78
9. V-29-2-10 1.6 167.1 141.7 0.878 0.59 0.85 11.8 74
10. V-29-3-10 1.5 158.5 135.7 0.835 0.66 0.90 13.3 78
11. V-29-3-11 1.5 195.2 156.4 0.909 0.61 0.83 12.3 72
12. V-29-6-12 1.4 179.6 145.6 0.823 0.58 0.74 11.7 64
13. V-29-6-24 1.6 186.9 151.0 0.878 0.62 0.89 12.4 77
14. V-29-7-23 1.5 208.4 162.3 0.962 0.65 0.88 13.1 77
15. V-29-8-20 1.5 167.3 138.9 0.870 0.63 0.85 12.7 74
16. V-29-8-23 1.5 210.9 165.5 1.04 0.71 0.96 14.3 84
17. V-29-10-11 1.4 174.9 144.8 0.868 0.63 0.79 12.5 69
18. V-29-10-12 1.4 195.5 154.6 0.896 0.62 0.78 12.4 68
19. V-29-10-13 1.4 168.0 140.1 0.860 0.63 0.79 12.6 69
20. V-29-10-21 1.3 208.2 162.3 0.827 0.57 0.66 11.3 57
21. V-51-1-9 1.6 159.4 134.0 0.970 0.72 1.04 14.5 91
22. V-51-3-3 1.6 178.5 145.4 0.777 0.55 0.80 11.1 70
23. V-51-8-2 1.3 183.6 148.0 0.927 0.65 0.80 13.1 70
24. V-51-15-11 1.7 160.6 134.9 0.924 0.68 1.04 13.6 91
32. V-7-8-6 1.7 181.2 147.5 0.970 0.69 1.06 13.8 92
33. Lue Gim Gong 1.6 144.0 126.5 0.906 0.69 1.00 13.9 87
34. V-23-1-1 1.7* 159.0 135.4 0.888 0.66 1.02 13.3 89
SResults are the average for samples from two duplicate blocks. ""Calculated on basis of 87 trees per acre.
t Boxes per tree, 6-year average from five replicated blocks.










Table 14.-Comparison of peel oil content of fruit from trees with a different rootstock having a common scion.
16-Fruit Sample* Peel Oil*
Fruit Mean Mean ml peel % in Lbs/ Lbs/ton Lbs/
Yield fruit surface oil/ whole fruit tree fruit acre**
No. Rootstock Avgt wt (g) area (cm2) 100 cm2


FlC Sour Orange
F9U Carrizo Citrange
F9Q Trifoliate
F36F Citremon
FID Swt. Pineapple
F9R Willits Citrange
F9P Rusk Citrange
F36A Troyer Citrange
F9"O" Uvalde Citrange
FIH Cleopatra Mandarin
F9E Rangpur Lime
F9N Trifoliate (S.F.)
F36D Cunningham Citrange
F36C Sacaton Citrumelo
F9S Morton Citrange
F9C Rough Lemon
F1P Orlando Tangelo
F9K Grapefruit
F36C Sacaton Citrumelo


155.2
133.5
135.1
162.4
160.5
165.7
146.2
159.8
162.9
143.7
151.8
151.0
123.4
146.6
147.8
182.7
178.4
164.6
178.5


134.8
119.5
120.2
135.6
136.6
136.8
124.2
134.4
135.7
124.9
130.2
133.3
110.7
129.2
127.9
145.2
146.0
139.3
145.3


1.080
0.900
1.043
0.973
1.053
1.155
0.904
1.049
0.966
1.111
0.964
1.158
0.910
1.119
1.113
1.079
1.002
1.000
0.916


0.82
0.70
0.82
0.71
0.78
0.84
0.67
0.77
0.70
0.84
0.73
0.89
0.72
0.86
0.84
0.75
0.72
0.74
0.86


0.59
0.51
0.22
0.58
0.71
0.30
0.30
0.56
0.63
0.61
1.0
0.24
0.39
0.70
0.68
0.88
0.84
0.60
0.54


16.4
14.1
16.3
14.2
15.7
16.7
13.5
15.5
14.1
16.9
14.5
17.9
14.3
17.3
16.9
15.0
14.4
14.8
17.2


1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
OD 12.
13.
14.
15.
16.
17.
18.
19.


Results are the average for fruit picked from two duplicate blocks.
* Calculated on basis of 87 trees per acre.
t Boxes per tree, 6-year average from five replicated blocks.







Data in Table 14 show that the peel oil content of 'Valencia'
fruit, from a common scion grown on 19 different rootstocks,
ranged from 13.5 to 17.9 pounds of oil per ton of fruit. The
particular scion used (Val. 16-14-22), gave the highest yield
of oil in the budwood selection (15.7 pounds per ton of fruit),
and it can be seen that some rootstocks seem to suppress oil
yields while others increased oil yields. Mean fruit weight and
mean surface area did not show any significant relationship to
peel oil content. Analysis of variance showed a significant dif-
ference in peel oil content. Rootstock F9N trifoliate (S.F.) gave
the best yield of oil on a per ton of fruit basis, but further
work is necessary before a recommendation can be made as to
a preferred rootstock.
The aldehyde content of the three Brazilian 'Valencia' oil
samples obtained from the same budwood on different root-
stocks were 1.26, 1.44, and 1.73%, respectively, for trifoliata
orange, sweet orange, and 'Rangpur' lime. Aldehyde content of
citrus oils has been considered one of the more important indi-
cators of high quality oil, and rootstock apparently has a pro-
found influence on the aldehyde content of orange oil.



E SURFACE VARIATION IN
0 PEEL OIL CONTENT
0O0.60
en
0
0
S0.55-


S0.50- .--:--o '-
Ld I
U ,--South
a- 045 North
3 045- I
2 -East
I 3 Valencia oranges ...,West
1 4 I I I I i
Stem-end Equator Stylar-end
SURFACE LATITUDE OF DISC REMOVAL

Figure 24.-Variation in peel oil content of peel discs from different por-
tions of the surface of Florida 'Valencia' oranges.

53







Peel oil production has been combined with fruit production
to calculate the pounds of peel oil produced per tree and per
acre so as to further evaluate the rootstock (Table 14) and
budwood (Table 13) studies. On this new basis, budwood selec-
tion seemed to have the greatest influence on yield of peel oil.
The overall best result was obtained with the 'Valencia' seed-
ling selection, Val. 16-14-22, which had one of the better fruit
production records, and also produced a calculated equivalent
of 1.27 pounds of peel oil per tree or 111 pounds per acre.
Considerably greater yields of fruit and peel oil could probably
be expected in the Ridge area of Florida, since Indian River
fruit yields have a history of lower production.
Figure 24 illustrates the variation in peel oil content at
different sampling positions on a Florida 'Valencia' orange by
showing both the sampling latitude and the side of the fruit that
was sampled vs oil content. The stylar end and the south side
of the fruit appeared to have a greater quantity of oil than
the other latitudes or quadrants.
Bitter Orange Oil.-The authors have examined one lot
of bitter orange oil produced by the FMC in-line extractor
and report these values:

Sp. gray. 250/250 0.8467
20
Ref. ind. 77 1.4739
D
20
Ref. ind. of 10% dist. 7 D 1.4720
Difference 0.0019
25
Opt. rot. a +94.23
25
Opt. rot. of 10% dist. a +96.37
Difference +2.14
Aldehyde content % 0.74
Evaporative residue % 4.12

The bitter orange oil possessed a somewhat bitter flavor and
slightly tangerine-like odor.
Juice Oil vs Coldpressed Oil.-During the manufacture of
baby or infant juices, it is customary to centrifuge the juice
in order to lower the oil content. 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 that is
typical of fresh orange juice and quite different from cold-
pressed orange oils. The physicochemical properties for these
oils are shown in Table 15 and compared with a typical cold-
pressed 'Valencia' orange oil.
The ratio of the oxygenated components, Table 16, show that
the juice oils are low in aldehyde content and high in ester
content as compared to a coldpressed oil. The ester content of
the juice oils is some 7 to 18 times greater than that of a cold-
pressed oil, and this change in ratio of flavor components is

Table 15.-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 In-Line FMC In-Line
Property
Sp. gray. 25 C/25 C 0.8427 0.8501 0.8427

Ref. ind. 1t20 1.4730 1.4740 1.4730
D
Ref. ind. 10% dist. 7 2 1.4723 1.4724 1.4718

Difference 0.0007 0.0016 0.0012

Opt. rot. a 2D +97.22 +90.82 +97.42

Opt. rot. 10% dist. ac +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 16.-Ratio of the oxygenated components of Valencia juice oils as
compared with coldpressed Valencia orange oil.
Type oil ..... Juice Oil Coldpressed Oil
Extractor ....... Brown Reamer FMC In-Line FMC In-Line
Compound % % %
Aldehyde 36.5 11.9 59.6
Ester 28.8 68.9 3.7
Alcohol 22.2 12.2 31.9
Acid 12.7 7.0 4.8
100.0 100.0 100.0

probably responsible for the fruity note in the juice oils. The
two juice oils are quite different in chemical composition, which
is undoubtedly due to the difference in the type of equipment used
to express the juice.
The Chemical Composition of Coldpressed 'Valencia' Orange
Oil.-The isolation and identification of the flavor components
found in orange peel oil has been a subject of considerable re-
search by many investigators (11,36,37,38,40,61,71,79,81,82,83,
102,105) since the development of gas chromatography as an
analytical tool particularly adapted for the rapid evaluation of
citrus oils. More than 200 different flavor compounds have been
found in coldpressed orange oil, but only 122 have been positively
identified, as shown in Table 17.
Aldehydes A, B, C, D, and E are a, /3-unsaturated R-CH =
C-CHO, R, and R' straight chain CH3(CH2)n; N is 5, 6, 7, or 8.
Comparison of Commercial Orange Oils Made by Seven Dif-
ferent Processes.-It is apparent from the data in Table 9 that
each method used to extract the oil gives a product that is
slightly different in its overall physical and chemical character-
istics. The oils obtained by the various methods of extraction
can be randomly divided into each of three groups or cate-
gories as follows: 1) Pipkin roll, screw press, and FMC rotary,
2)FMC in-line and Brown shaver, and 3) Fraser Brace ex-
coriator and AMC scarifier. The oils in group 1 are generally
considered to have much better top-note and bouquet than the
oils in group 3, while group 2 is intermediate between the two.
The Fraser-Brace excoriator and AMC scarifier use rasping or
abrasion to obtain the oil, which seems to result in higher
values for evaporation residue and specific gravity than oils
recovered by procedures that rupture the oil cell by pressure.











Table 17.-The chemical composition of coldpressed Valencia orange oil.


TERPENES:

a-thujene
a-pinene
camphene
2,4-p-menthadiene
sabinene
myrcene
5-3-carene
a-phellandrene
a-terpinene
d-limonene
p-terpinene
p-cymene
a-terpinolene
a-p-cubebene
a-p.-copaene
p-elemene
caryophyllene
farnesene
a-p-humulene
valencene
a-cadinene

ALDEHYDES:

formaldehyde
acetaldehyde
n-hexanal
n-heptanal
n-octanal
n-nonanal
n-decanal
n-undecanal
n-dodecanal
citral- neral
r geranial
citronellal
a-sinensal
p-sinensal
trans-hexen-2-al-1
dodecene-2-al-1
furfural
perillyldehyde
Aldehyde A
B
C
D
E

OXIDES:

trans-limonene oxide
cis-limonene oxide


ALCOHOLS:


KETONES:


methyl alcohol carvone
ethyl alcohol methyl heptenone
amyl alcohol a-ionone
n-octanol acetone
n-decanol piperitenone
linalool 6-methyl-5-hepten-2-one
citronellol nootkatone
a-terpineol
n-nonanol a,p-DIALKYL ACROLEINS:
trans-carveol
geraniol a-hexyl-p-heptyl acrolein
nerol a-hexyl-p-octyl acrolein
heptanol a-heptyl-p-heptyl acrolein
undecanol a-octyl-p-heptyl acrolein
dodecanol a-hexyl-p-nonyl acrolein
elemol a-octyl-p-octyl acrolein
cis-trans-2,8-p-menthadiene-l-ol
cis-carveol a-heptyl-p-nonyl acrolein
1-p-methene-9-ol
1,8-p-menthadiene-9-ol
8-p-methene-1,2-diol PARAFIN WAXES:
isopulegol
borneol
methyl heptenol n-C21H44
hexanol-1 2-methyl-C2,H43
terpinen-4-ol 2-m


ESTERS:


n-C,,H4.,
2-methyl-C22H45


perillyl acetate n-C.2H48
n-octyl acetate
bornyl acetate 3-methyl-C,3H4,
geranyl format
terpinyl acetate n-C24H30
linalyl acetate
linalyl propionate 2-methyl-C24H49
geranyl acetate n-CH,,
nonyl acetate -
decyl acetate 3-methyl-C25H,5
neryl acetate
citronellyl acetate n-C2,H.4
ethyl isovalerate methyl
geranyl butyrate 2-methyl-C2,H,
1,8-p-menthadiene-9-yl-acetate
n-C,7Hs,


ACIDS:

formic
acetic
caprylic
capric


3-methyl-C27H,,
n-C2,H.8
2-methyl-C28H57
n-C2,,H,











Table 18.-Comparison of Florida coldpressed orange oil with oils from other sources.
U.S.P. XVII Florida California Italian Guinea Brazilian
Specifications Coldpressed Orange Coldpressed Coldpressed Coldpressed Coldpressed
Property Coldpressed (all methods) Orange Orange Orange Orange
Orange
Orange Max. Min. Avg. Max. Min. Max. Min. Max. Min. Max. Min.

Specific 0.842
gravity to 0.846 0.842 0.843 0.846 0.843 0.846 0.843 0.845 0.840 0.847 0.842
(25C/25C) 0.846
Refractive 1.4720
index to 1.4743 1.4718 1.4724 1.4742 1.4731 1.4740 1.4729 1.4742 1.4721 1.4747 1.4723
(20C) 1.4740
Evaporation not less than
residue 1.7% (43 mg/ 4.9 1.1 2.2 5.1 3.5 4.3 1.4 2.4 1.1 4.8 2.2
% 3 ml)
Optical not less than
rotation +94 and not +98.05 +94.98 +96.75" +98.330 +94 +97.170 +95.5 +980 +94 +97.87" +95.0
(25C) more than +990
in 100 mm tube







Since the method of extraction not only affects the physico-
chemical properties of the oil but the flavor qualities as well,
it therefore becomes an important consideration in the selection
of an oil for any given use or purpose.
Comparison of Florida Coldpressed Orange Oil with Oils
from other Sources.-Data presented in Table 18 show how
Florida orange oil compares with similar types of oils from
California and various foreign countries. Data in these tables
for Florida oils are based on results obtained from seven dif-
ferent processes for oil extraction. The data for the oils from
other sources are those given by Guenther (24,25,28) and are
based upon analyses of many samples of these oils in the labora-
tories of Fritzsche Brothers, New York.
From the comparison of the properties presented in this
table, it is evident that Florida citrus oils can be equal or
superior to essential oils from any other source.

Distilled Oils
Distilled Orange Oil.-In Table 19 maximum and minimum
values are presented for nine samples of vacuum steam distilled
orange oils, which were secured from cannery deoilers. A com-
parison is made with California distilled orange oil. From this
comparison it is evident that the values for specific gravity,
refractive index, evaporation residue, and optical rotation are in
close agreement. A comparison between the aldehyde content


Table 19.-Comparison of Florida and California distilled orange oil.
Florida California
Property Max. Min. Average Max. Min.

Specific gravity 0.846 0.840 0.842 0.842 0.840
(250C/25C)
Refractive
index 7 20 1.4732 1.4715 1.4720 1.4730 1.4717
D

Evaporation 1.24 0.08 0.47 1.0 0.5
residue, %
Optical
rotation 25 +98.56 +95.92 +97.62 +99.1 +980
D
Aldehyde
content, % 2.48 1.72 1.99 -
(decyl)








of these two oils cannot be made, since values are not available
for the California oils.
By considering the values for coldpressed orange oil obtained
from all methods studied, it can be seen that the distilled oil
had an aldehyde content about 24% higher and an ester content
about 10% lower than the corresponding values for the best
quality coldpressed oils.
From these results, it was evident that large quantities of
aldehydes were removed from the citrus juice itself by the de-
oilers during commercial canning operations. Also, it is indi-
cated that removal of oil from the juice by the deoilers results
in fractionation of the peel oil originally present; so the small
quantity of oil which remains in the canned juice will have
different characteristics from either expressed or distilled oils.
Oil distilled from citrus fruit juice would seemingly have better
flavoring qualities than oil obtained by steam distillation.
Orange Essence Oil.-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 20.-Physicochemical properties of orange essence oils.
Property Maximum Minimum Average

Sp. gray. 250 C/25 C 0.8428 0.8403 0.8415
Ref. ind. 1 20 1.4725 1.4721 1.4723
D
Opt. rot. a 25 +99.16 +97.68 +98.42
D
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 acetylation 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









Table 20 shows the physicochemical properties for 15 essence
oils analyzed during 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 char-
acteristic 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 (39) and used as
a flavor enhancer.


Table 21.-Chemical composition of terpeneless Valencia orange essence oils.
Peak Peak
No. Compound % No. Compound %


1 acetaldehyde
2 hexane
3 hexanal
4 acetone, methanol
5 ethyl acetate
6 ethanol
7 ?
8 ?
9 ?
0 a-pinene
1 ?
2 ?
3 ?
4 ?
5 ?
6 /-myrcene
7 heptanal
8 ?
9 d-limonene
0 ?
1 ?
2 ?
3 ?
4 ?
5 octanal
6 ?
7 ?
8 hexanol
9 methyl heptenone
0 ?
1 ?
2 ?
3 ?
4 ?
5 nonal
6 ?
7 ?
8 ?
9 ?
0 ?
.1 heptanol
-2 ?
* a-limonene form


citronellal-a*
octyl acetate
?fuural
furfural
7


decanal
linalool
octanol
linalyl acetate
citronellyl acetate-b *
?

nonyl acetate
terpinene-4-ol
undecanal,
linalyl propionate
geranyl formate-b
?7


5.2 60 ?
0.3 61 ?
0.3 62 nonanol, citronellol-b
tr 63 citronellyl acetate-a,
0.2 geranyl acetate-b
0.4 64 ?
11.5 65 ?
0.1 66 decyl acetate
tr 67 a-terpineol
0.3 68 a-terpinyl acetate-d
0.1 69 borneol, geranyl
0.2 formate-a,
0.2 a-terpinyl acetate
tr 70 ?
0.1 71 dodecanal
0.1 72 neryl acetate-b
2.1 73 geranial
0.2 74 -carvone
tr 75 geranyl acetate-a,
0.2 neryl acetate-a
0.1 76 ?
0.4 77 trans-carveol
0.3 78 undecanol
0.4 79 cis-carveol
** b-terpinolene form


0.3
1.0
1.8
0.5
0.1
12.1
22.4
0.8
0.3
1.3
0.7
1.2
0.9
2.7

0.7
3.0
0.9
0.2
0.1
0.2

1.9
0.2
0.8
1.9
1.9
0.6


:4:







Terpeneless oils were prepared from three different blends
of 'Valencia' essence oil, and the average chemical composition
of these three oils is shown in Table 21. The compounds are
listed in the order in which they emerged from a carbowax
20 M column. The ratio of the oxygenated components of these
oils is approximately as follows: aldehydes 45%, esters 30%,
alcohols 24%, and free acids 1%.
In the early stages of essence production it was not unusual
to obtain an oil with an off-odor commonly referred to as "wet-
dog" aroma. By chemical analyses, the "wet-dog" essence oils
were found to have 28.2% less esters and 27.6% more alcohols
than good essence oils. Two of the most noticeable chemical
differences were a greater quantity of terpinen-4-ol and a de-
crease in geranyl format. This suggested that one of the rea-
sons for the "wet-dog" aroma was too much heat in the essence
recovery units which broke down the esters, under the acidic
conditions of the juice, to alcohols and acids. Subsequently,
this problem was corrected by lowering the temperature in the
essence recovery units and keeping them flooded to prevent
localized overheating.
Good quality essence oils possess an unusual rich fruity
flavor and aroma that merits their consideration for use in oil
add back to juice, perfumes, beverages, chewing gum, condi-
ments, etc.
OIL OF GRAPEFRUIT AND SHADDOCK
In recent years, the demand for Florida coldpressed grape-
fruit oil has increased phenomenally due to the popularity of
carbonated grapefruit beverage drinks. Two general types of
grapefruit oil are currently manufactured in Florida: white
and red. White grapefruit oils are produced primarily from
'Duncan Seedy' and 'Marsh Seedless'. Red grapefruit oils are
made from 'Ruby Reds' and occasionally from 'Foster' and
'Thompson' pinks. The odor and flavor of grapefruit oil is ex-
tremely delicate and characteristic of the fruit from which it is
extracted. Therefore, the greatest care is exercised to avoid
admixture with other citrus peels or fruits. With present day
methods for handling fruit only pure oils are produced in
Florida.
Coldpressed Oil of Grapefruit
Genetic Relationship of the Common Types of Grapefruit.-
Since readers may not be familiar with the genetic relationship










Citrus grandis


SHADDOCK
or
PUMMELO





Citrus paradise



SEEDED GRAPEFRUIT
Thought to be a sport or
variant of the shaddock





MARSH SEEDLESS VARIETY FOSTER PINK VARIETY
A sport or variant (Seeded)
of a seeded type
Sport of Walters




THOMPSON PINK VARIETY
Sport of Marsh Seedless





RUBY RED AND OTHER RED MEATED VARIETIES

(Seedless)
Sport of Thompson Pink
Figure 25.-Genetic relationship of the common types of grapefruit.


of grapefruit, a schematic (Figure 25) is given to show the
family tree of common grapefruit cultivars. It has been com-
monly accepted that grapefruit was a sport from the 'Shaddock,'
and probably for this reason oil of 'Shaddock' has beein included
with oil of grapefruit. Actually, this relationship of 'Shaddock'
to grapefruit has not been established, but rather surmised since
the grapefruit resembles the 'Shaddock.' The grapefruit and
shaddock may not be related, or the grapefruit may be a natural
hybrid.







Methods of Expressing Grapefruit Oil and Yield of Oil.-
The same general processing techniques are used to extract
grapefruit oil from residual peel and whole fruit as described
in methods of commercial manufacture. It should be noted that
the oil glands are located deeply in the peel, and that, in addition,
the peel contains a very thick spongy albedo layer, which has
a tendency to absorb the oil as soon as it is released from the
fruit. The authors (34) have found the yield of oil to vary
from season to season, as shown in Table 22. The quantity of oil
contained in grapefruit is approximately one-half that found in
'Valencia' oranges. In commercial practice, actual yields fall
far short of theoretical and range from 1.5 to 3.0 pounds of oil
per ton of fruit.

Table 22.-Peel oil content of grapefruit cultivars as related to seasons.
Cultivars Lbs Oil/ % Oil
Studied Season Ton Fruit in Whole Fruit

Duncan 1968-69 5.1 7.1 0.26 0.36
1969-70 4.8 6.8 0.24 0.34
Marsh 1968-69 6.2 7.8 0.31 0.39
1969-70 5.1 7.5 0.26 0.38
Foster Pink 1969-70 5.3 7.5 0.27 0.38

Characteristics of Coldpressed Grapefruit Oil Prepared in
Pilot Plant from Various Cultivars.-The physical and chemical
properties of grapefruit oil expressed from five different culti-
vars are presented in Table 23. These samples represent pure
grapefruit oil from known cultivars of grapefruit prepared in
the Citrus Experiment Station's Pilot Plant using an experi-
mental model of the Fraser-Brace excoriator. These data re-
vealed significant differences in the physicochemical properties
of oils prepared from five different cultivars.
Comparison of Commercial Grapefruit Oils Mode by Seven
Different Processes.-Table 24 shows the physicochemical prop-
erties for 100 commercial samples of grapefruit oil expressed
by seven different methods. Samples were taken from lots of
oil ranging from 3,500 to 11,000 pounds. These oils can be
randomly grouped into three general types or categories as fol-
lows: 1)Pipkin roll, screw press, and FMC rotary. 2) FMC
in-line and Brown shaver, and 3) Fraser-Brace and AMC scari-
fier. Values for evaporation residue and specific gravity seem
to be highest for those processes utilizing scarifying or rasping







methods to remove the oil, while values for optical rotation seem
to be lower. However, each particular process gives an oil with
individual and characteristic properties that sets it apart from
oils made by each of the other processes.
Comparison of Red and White Grapefruit Oils.-The red and
white grapefruit oils used in this study (64) were obtained from
three different commercial plants employing either a screw press
or FMC in-line extractors for oil recovery. These oil samples
were dried over anhydrous sodium sulfate and stored in glass
one year under nitrogen at 40' F.
The physical and chemical properties for the six grapefruit
oils are shown in Table 25. It can be seen from these data that
the values for specific gravity, refractive index, difference be-
tween original oil and 10% distillate for refractive index and
optical rotation, and evaporation residue without exception were
highest for red grapefruit oils, while the values for optical ro-
tation and aldehyde content were lower than those for white
grapefruit oils.
Terpeneless oils were prepared, by the method of Kirchner
and Miller (72), to better study the composition of the oxygen-
ated components and eliminate the high percentage of terpene
from the coldpressed oils. The approximate relative concentra-
tions of the various components are shown in Table 26.
The compounds are listed in the order in which they emerged
from the Carbowax 20M column. From these data, it can be
seen that the chemical composition of the oils was quite variable
and that the two main components present in these oils were
octyl and decyl aldehydes. In white grapefruit, the ratio of
octyl to decyl aldehyde was found to range from 1:1.1 to 1:1.4.
In red grapefruit these values were reversed and ranged from
1.2:1 to 1.3:1. Compositional changes of this magnitude would
undoubtedly alter the flavor characteristics of the oils.
The red grapefruit oils contained a small quantity of linalool.
Linalool was apparently absent in white grapefruit oils and
would therefore offer the best criterion for resolving the type
fruit from which the oil was manufactured.
The spectrophotometric analyses of the coldpressed grape-
fruit oils in ultraviolet are shown in Table 26. The CD and
peak absorption values for the red grapefruit oil are slightly
higher than those for white grapefruit.
On the basis of these findings, a procedure has been devel-
oped whereby it is possible to differentiate between red and
white Florida grapefruit oils as follows:
















Table 23.-Characteristics of coldpressed grapefruit oil prepared in pilot plant from various cultivars.
Refrac-
Refrac- tive Optical Aide- Evapo-
Variety Specific tive Index Optical Rotation hyde Ester ration
of Gravity Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Fruit 25C/25C r 20 Distillate ence 25 Distillate ence tent tent due
D 20 a D 25 % % %
D YD


Duncan
Marsh Seedless
Thompson Pink
Ruby Red
Foster Pink


0.8560 1.4773 1.4716 0.0057 +90.25 +97.23 +6.98 1.30 3.59 10.50
0.8570 1.4772 1.4715 0.0063 +88.61 +97.23 +8.62 1.58 3.55 10.64
0.8558 1.4773 1.4715 0.0058 +90.04 +96.03 +3.99 1.46 3.47 10.29
0.8556 1.4771 1.4714 0.0057 +89.38 +97.03 +7.65 1.54 4.41 9.73
0.8588 1.4779 1.4711 0.0068 +86.74 +96.23 +9.49 1.66 3.70 13.46


a1








1. Ratio of octyl to decyl aldehyde
White-1:1.1 to 1:1.4
Red-1.2:1 to 1.3:1
2. Quantity of linalool
White-absent
Red-present

It would seem advisable to manufacture and store red and
white grapefruit oil separately. This procedure would give the
essential oil trade a choice or preference between these two dif-
ferent and distinct types of oil.
Nootkatone Content of Expressed 'Duncan' Grapefruit Oil
as Related to Fruit Maturity.-Nootkatone, a sesquiterpene ke-
tone with a carbon skeletal structure identical to valencene, is
found in expressed grapefruit oil and in peel-oil-free juice. It
is the present feeling in the flavor industry that good grapefruit
flavor is related to the nootkatone content of expressed grape-
fruit oil.
'Duncan' grapefruit (17) were processed throughout the
1963-64 season from the date the fruit first reached legal matur-
ity and at 6-week intervals thereafter. Oil samples were dried,
using anhydrous sodium sulfate, and were put into amber glass
bottles, which were filled completely under nitrogen and sealed
with cork stoppers as well as screw caps. The samples were
stored at 400 F until the last oil sample was aged for 6 months.
A progressive increase in the nootkatone content of the ex-
pressed grapefruit oil from 0.065 to 0.810% was observed as the
fruit became more mature (Table 27). The nootkatone content
of the oil could probably be used as a measure of fruit maturity.
This is greater than a tenfold increase, and it then follows that
the most advantageous time for the processor to recover grape-
fruit oil in order to obtain an oil with the maximum concentra-
tion of nootkatone would be in May or June (or at the end of
the processing season).
The seriously lower yield of oil obtained when processing
grapefruit of greater maturity requires careful inquiry by the
processor as to the importance of nootkatone or good grapefruit
flavor to the potential buyer of his oil. The yield of oil recovered
from the fruit diminished from 2.55 pounds per ton fruit to
0.50 pounds per ton fruit as the fruit ripened. There is the
likelihood that a compromise can be made between yield and
good flavor quality in order to make oil production economically
feasible.








Table 24.-Maximum and minimum values for the properties of coldpressed grapefruit oil produced by various methods.


Method of
Extraction Pipkin Roll Screw Press Fraser-Brace FMC Rotary FMC In-Line AMC Scarifier Brown Shaver
No. of
Samples 4 13 32 5 36 4 6
Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min.
Property
Sp. grav.
25*C/25oC 0.8537 0.8508 0.8552 0.8483 0.8610 0.8539 0.8649 0.8515 0.8576 0.8476 0.8715 0.8520 0.8583 0.8531

Ref. ind. r120 1.4767 1.4746 1.4769 1.4749 1.4785 1.4764 1.4777 1.4752 1.4784 1.4751 1.4836 1.4762 1.4775 1.4766

Ref. ind.
10% dist. 7 20 1.4714 1.4702 1.4721 1.4713 1.4716 1.4706 1.4713 1.4698 1.4722 1.4715 1.4719 1.4714 1.4721 1.4713

Difference 0.0053 0.0038 0.0051 0.0030 0.0072 0.0052 0.0064 0.0054 0.0068 0.0033 0.0117 0.0048 0.0062 0.0047

Opt. rot. a25 +92.96 +92.03 +95.56 +91.07 +90.68 +85.14 +91.97 +88.92 +93.95 +90.60 +93.74 +87.02 +93.04 +90.49

Opt. rot.
10% dist. 25+97.77 +96.29 +98.53 +96.60 +98.05 +96.03 +98.14 +95.52 +98.91 +96.55 +98.82 +97.86 +98.28 +97.33

Difference +4.81 +3.68 +6.10 +2.96 +11.29 +5.99 +6.60 +4.03 +6.40 +3.44 +14.56 +4.12 +6.88 +4.60
Aldehyde
content % 1.61 1.49 1.57 1.30 2.06 1.01 1.67 1.12 1.75 0.74 1.91 1.02 1.56 1.17
Ester
content % 4.38 2.77 3.68 2.48 5.25 2.91 4.66 2.11 -
Evaporation 7.18 10.45 7.23
residue % 7.72 2.82 8.24 4.57 .14.59 9.59 10.12 -7.85 9.39 5.22 18.16 7.18 10.45 7.23














Table 25.-Physical and chemical properties of coldpressed red and white grapefruit oils.


Extractor .....................
Type O il ......................
Property
Sp. grave. 250C/25C
20
Ref. ind. 77 2
D
Ref. ind. 10% dist. 7 22
t Difference
25
Opt. rot. a D

Opt. rot. 10% dist. a2D

Difference

Evaporation residue, %

Aldehyde content, %


FMC In Line Screw Press
White Red White Red


0.8539

1.4759

1.4719

0.0040

+92.87

+97.02

+4.15

6.69

1.69


0.8539

1.4761

1.4719

0.0042

+93.27

+97.22

+3.95

5.99
1.42


0.8604

1.4786

1.4718

0.0068

+90.67
+96.82

+6.15
9.39

1.23


0.8576
1.4778

1.4719

0.0059

+90.87

+97.02

+6.15

8.02

1.23


0.8534

1.4759

1.4718

0.0041

+92.67

+ 97.04

+4.37

6.32

1.56


0.8552

1.4766

1.4718

0.0048

+91.07

.+96.84

+5.77
7.12

1.38









Compound
Extractor ......
Type Oil ......
a-pinene
?

f-myrcene
heptanal

d-limonene
octanal
?
methyl heptenone
nonanal

methyl heptenol
?
octyl acetate
citronellal
decanal

linalool
octanol
linalyl acetate
nonyl acetate
undecanal

nonanol
geranyl acetate
decyl acetate
decanol
dodecanal

citral
terpineol
carvone
neryl acetate
nerol
geraniol


Table 26.-The composition of terpeneless red and white grapefruit oils.
% Composition
FMC In Line
White Red White


0.75
0.37
0.37
0.75
2.62

3.75
17.99
0.75
2.25
4.49

1.87
0.37
4.12
1.50
25.85


0.90
0.72
0.72
0.90
1.44

2.71
19.51
2.35
2.35
5.23

1.44
0.90
4.15
1.08
26.01


1.62
3.61
4.87
4.69

0.36
0.90
0.72
1.81
3.61

3.25
3.07
0.90
0.18
tr
tr


0.29
0.36
0.36
0.71
0.89

2.14
20.52
1.07
2.14
4.10

1.78
0.54
4.10
1.43
16.41

3.92
1.25
2.50
4.46
4.82

0.36
1.78
0.71
1.78
4.46

3.57
4.10
7.31
2.14
tr
tr


0.45
0.23
0.36
1.13
1.35

1.35
25.66
0.68
0.90
3.15

0.90
0.45
2.48
1.13
21.38

2.93
0.27
2.25
1.58
3.38

0.45
0.41
0.09
1.13
6.76

4.28
7.21
5.86
1.80
tr
tr


0.47
0.05
0.09
0.14
0.23

0.70
29.52
0.94
0.94
3.75

1.17
0.70
1.64
0.42
31.87


0.70
2.11
3.05
4.92

0.37
0.47
0.14
0.19
3.28

2.11
6.33
2.34
0.14
0.05
1.17


Screw Press
Red
0.62
0.04
0.42
1.66
1.04

3.12
25.81
1.04
1.46
3.75

0.83
0.62
2.70
1.25
20.81

2.08
1.25
2.91
2.08
4.16

0.42
0.83
0.29
0.42
4.37

1.66
6.66
5.41
1.25
0.83
0.21












Ratio: octyl/decyl


CD


CD
Peak
MP
* tr trace


1/1.4


0.285
0.325
319.2


1/1.3 1.3/1

U.V. Spectrum Mg loge 0.25 g
100 ml
0.318 0.533
0.368 0.653
319.0 319.2


1.2/1



0.323
0.393
319.0


1/1.1



0.258
0.305
319.0


1.2/1



0.260
0.330
320.0


--







Table 27.-Nootkatone concentration and physicochemical properties of expressed
maturity.


'Duncan' grapefruit oil as related to fruit


Sample No. ............. ... 1 2 3 4 5 6
Processing Date .............. 11/19/63 12/31/63 2/11/64 3/24/64 5/5/64 6/16/64
Oil yield Ibs/ton fruit .......... 2.25 2.38 1.25 1.33 1.23 0.50

Sp. gray. 25oC/25C 0.8538 0.8518 0.8517 0.8514 0.8515 0.8531
20
Ref. ind. 7 2 1.4765 1.4761 1.4760 1.4759 1.4761 1.4764
D

20
Ref. ind. 10% dist. D1 1.4714 1.4716 1.4717 1.4718 1.4720 -
D
Difference 0.0051 0.0045 0.0043 0.0041 0.0041 -

Opt. rot. a25 +92.77 + 92.97 +93.17 +93.57 +93.13 +92.71
D

Opt. rot. 10% dist. x 25 +97.64 +97.84 +98.24 +98.64 +98.55
D
Difference + 4.87 + 4.87 +5.07 +5.07 +5.42 -
Aldehyde content, % 1.43 1.62 1.80 1.76 1.79 1.61
Evaporation residue, % 7.89 6.87 7.48 7.25 7.26 8.42
Acid no. 1.33 1.14 1.54 1.46 1.40 1.66
Free acid, % 0.34 0.29 0.39 0.38 0.36 0.43
Ester no. before acetylation 10.88 9.97 9.34 8.51 9.36 9.62
% ester before acetylation 3.80 3.48 3.26 2.97 3.27 3.36
Ester no. after acetylation 15.45 13.33 13.17 13.24 13.08 12.65
% ester after acetylation 5.40 4.66 4.60 4.63 4.57 4.42
Free alcohol, % 1.26 0.93 1.06 1.30 1.03 0.83
Total alcohol, % 4.24 3.66 3.62 3.64 3.59 3.48
Nootkatone, % 0.065 0.285 0.503 0.693 0.750 0.810








It can be seen from these data that the values for specific
gravity, refractive index, optical rotation, evaporation residue,
acid number, per cent free acid, per cent ester before acetyla-
tion, and per cent free alcohol remained more or less constant
throughout the processing season. There was a tendency for
the per cent total alcohol and per cent ester after acetylation
to decrease, but this is due to aging of the oil samples rather
than to fruit maturity. If the per cent nootkatone, a ketone,
is deducted from the aldehyde content, a gradual decrease occurs
in the aldehyde content which is characteristic for the aldehyde
content of orange oil. However, nootkatone increases at a faster
rate than the aldehyde decrease, so the net effect is an overall
increase in total carbonyl content.
Flavor of 'Duncan' Grapefruit Oil vs Fruit Maturity.-The
expressed 'Duncan' grapefruit oils (Table 28) were submitted
to three different panels of experts for organoleptic evaluation
(66). In consideration of these data, it can be seen that there
is no clear-cut preference for any particular sample. Sample
No. 1, prepared from early season fruit, was rejected by two
panels and accepted by one.
One panel was influenced by the nootkatone concentration,
while the other panel was influenced by the aldehyde concentra-
tion. The third panel was intermediate between the two.
Majority opinion would indicate that Samples No. 3 and 4 are
preferred. These samples contained the highest aldehyde con-
tent, and the nootkatone concentration varied between 0.50 and
0.70%. On the basis of these findings, it would seem advisable
to manufacture grapefruit oils during the months of February,
March, and April to obtain oils with the best odor and flavor
characteristics. The production of early season oils should be
avoided, since they appear to have less desirable odor and flavor
qualities.
Curing Florida Grapefruit Oils.-Commercial practice (62,
65, 66) has shown that expressed grapefruit oils should be care-
fully aged for 6 to 12 months to develop their full, rich-bodied,
distinctive grapefruit character. Since there was no published
information which explained this flavor improvement, a study
was made to determine if grapefruit oils undergo chemical
transformations that could effect a beneficial flavor change.
Oil samples used in this study were obtained from commer-
cial processors utilizing the FMC in-line extractor with mist
spray attachment. The grapefruit were of the 'Duncan' variety.
Samples were collected directly from the centrifuge and dried















Table 28.-Organoleptic evaluation of expressed Duncan grapefruit oil as related to fruit maturity.

TEST PANEL ............ A B C
Participants ............. 4 3 15
Processing % %
date No. Nootkatone Aldehyde Odor Flavor Odor Flavor Odor Flavor

11/19/63 1 0.065 1.43 Accept Accept 2-Reject 1-Accept 3-Reject Reject Reject
12/31/63 2 0.285 1.62 Accept Accept 1-Reject 2-Accept 2-Reject 1-Accept Superior Superior
2/11/64 3 0.503 1.80 Accept Accept 3-Accept 1-Reject 2-Accept Superior Superior
3/24/64 4 0.693 1.76 Accept Superior 1-Reject 2-Accept 3-Accept Accept Accept
5/5/64 5 0.750 1.79 Accept Superior 1-Reject 2-Accept 1-Reject 2-Accept Reject Reject
6/16/64 6 0.810 1.61 Accept Superior 1-Reject 2-Accept 2-Reject 1-Accept Accept Accept









using anhydrous sodium sulfate. Each sample was subdivided
immediately by filling into amber glass bottles which were sub-
sequently flushed with nitrogen and sealed with cork stoppers
as well as screw caps. One sample was analyzed immediately,
while the others were stored at 40' F and analyzed at storage
intervals of 3, 6, 9, and 12 months.
A second set of samples was prepared later from a similar
freshly separated grapefruit oil which was again analyzed im-
mediately. The subsamples were stored at 0, 40, 60, and
800 F for 6 months, at which time the samples were analyzed.
Composition of Expressed Grapefruit Oil as Related to
Curing at 400 F.-In this portion of the study, the subdivided
samples of expressed 'Duncan' grapefruit oil were stored at
400 F. An aliquot was analyzed immediately and each of the
sealed samples reanalyzed at consecutive 3-month intervals. The
physical and chemical properties of these samples are shown
in Table 29. These data show that the values for specific gravity,
refractive index, optical rotation, evaporation residue, aldehyde,
acid number, per cent free acid, ester number before acetylation,
per cent ester before acetylation, and per cent total alcohol
remained relatively constant while the values for ester number
after acetylation, per cent ester after acetylation, and per cent
free alcohol decreased with aging or curing of the oil. This is


Table 29.-Physical and chemical properties of expressed grapefruit oils
cured at 40* F.
Storage Time
Property Initial 3 Mos. 6 Mos. 9 Mos. 12 Mos.
Sp. gray. 25*C/25C 0.8489 0.8489 0.8489 0.8487 0.8489
Ref. ind. 20 1.4756 1.4753 1.4755 1.4754 1.4755
D
10% dist. 1.4721 1.4719 1.4721 1.4721 1.4721
Difference 0.0035 0.0034 0.0034 0.0033 0.0034
Opt. rot. 25 +94.72 +95.13 +95.16 +94.86 +94.47
D
10% dist. +98.27 +98.33 +98.56 +98.26 +98.47
Difference +3.55 +3.20 +3.40 +3.40 +4.00
Evap. res., % 5.14 4.95 5.12 5.04 5.04
Aldehyde, % 1.31 1.26 1.27 1.25 1.30
Acid no. 0.61 0.46 0.46 0.47 0.47
Free acid, % 0.16 0.10 0.12 0.12 0.12
Ester no. before acetylation 6.14 6.56 6.28 6.93 6.56
% ester before acetylation 2.15 2.29 2.19 2.42 2.29
Ester no. after acetylation 10.27 9.70 9.35 9.01 8.52
% ester after acetylation 3.47 3.38 3.26 3.15 2.98
Free alcohol, % 1.14 0.86 0.85 0.57 0.54
Total alcohol, % 2.46 2.66 2.58 2.47 2.35









associated with the decrease in per cent free alcohol which is
primarily related to the disappearance of linalool. Ultraviolet
and infrared data were collected on these oils. The absorption
characteristics of all oil samples remained virtually the same
and did not reflect any of the observed chemical changes.
Terpeneless oils were prepared from these same samples
and used for the gas chromatographic comparisons as shown in
Table 30. It can be seen from these data that Peaks No. 4, 5,
7, 11, 13, 21, 30, and 32 decreased while Peaks No. 16, 18, 33,
34, 35, 38, 40, 41, 42, and 43 increased. When grapefruit oils
are freshly prepared, they possess an orange-like by-note that
disappears on storage. The most striking change in the com-
position of these samples was the complete loss of linalool (Peak
21, Table 33). This change is very likely responsible for the
disappearance of the orange-like character. This study was
concerned only with the oxygenated components, since they were
thought to contribute most to the flavor of an oil. However,
since many changes have been shown to occur which were not
anticipated, it is quite likely that the terpene fractions undergo
similar changes that could contribute to flavor. There are sev-
eral possible ways in which these xearrangements or changes
in chemical composition could be explained; it is not the intent
to explore these possibilities with the limited data at hand, but
rather to show that expressed grapefruit oils during storage
do undergo compositional changes which apparently improve the
flavor of the oil.
Composition of Expressed Grapefruit Oil as Related to Dif-
ferent Storage Temperatures.-When it was found that the
chemical composition of expressed grapefruit oil actually
changed with length of storage at 400 F, another experiment
was undertaken to determine if increased storage temperatures
would shorten the time necessary to effect these changes. Con-
sequently, a second commercially prepared sample was obtained
and aliquots were stored for 6 months at temperatures of 0,
40, 60, and 800 F. Initially and at the end of this curing
interval, terpeneless oils were prepared and analyzed. Gas
chromatographic comparisons are shown in Table 31. These
data show that Peaks No. 5, 10, 14, 24, 27, 33, and 35 decreased,
while Peaks No. 18, 21, 39, 40, 42, and 43 increased. Here again,
almost the same changes occurred, except at the higher storage
temperatures of 60 F and 80 F the changes were greatly ac-
celerated and linalool (Peak 24, Table 34) completely disap-
peared in 6 months at 80 F. In the first study, carvone was








found to increase with time of storage, but in this experiment
there was no change. Also, nonyl acetate remained constant in
the first study, but decreased in the second study. It then be-
comes apparent that each oil is slightly different and cannot,
therefore, be expected to follow an exact pattern. In each study,
however, methyl heptenone, methyl heptenol, neryl acetate, nerol,
and geraniol were found to increase, while linalool, citral, and
terpineol decreased. In both studies, linalool completely disap-
peared. There are several unidentified peaks that either de-
creased or increased, and it is not known if these are comparable
for the two oils.
If the linalool content was used as a criterion to determine
the proper curing procedure for expressed grapefruit oil, it
would follow that the most ideal storage temperature lies some-
where between 600 F and 80 F and is most probably in the
range of 65 F to 70 F. At this temperature, the holding time
could be reduced to 6 months or one-half of that at 40 F.
Recommendations for the Production and Proper Handling
of Expressed Grapefruit Oils.-Previous work by the authors
(66) has shown that expressed grapefruit oils should be made
during the months of February, March, and April to obtain
oils with the best odor and flavor characteristics. The production
of oil from grapefruit when it first reaches legal maturity should
preferably be avoided, since the odor and flavor is less desirable.
Taking this information into consideration, the following gen-
eral recommendations are made in regard to the production and
handling of Florida grapefruit oils:
1. Manufacture oil during the months of February, March,
and April.
2. Dewax at a temperature of -10 F to +-300 F.
3. Cure for 6 months at 65 F to 70 F prior to marketing.
If this procedure is followed, oils of superior quality will
result and customer acceptance should improve, thus favoring
a more profitable market for this commodity.
On standing or chilling, a yellowish to brown flocculent pre-
cipitate forms which may entirely disappear on warming. Grape-
fruit oils differ from orange oils in that this sediment will con-
tinue to precipitate for a period of about 60 days, and may
continue for a period of 2 years, but at least 95% of the wax
is removed within 2 months. The lower the temperature, the
more rapid the precipitation of the sediment. Although ap-
pearing voluminous, the precipitate is of light weight, amount-
ing to only about 1 or 2% of the total weight of the oil.







Table 30.--Change in composition of expressed Duncan grapefruit oil as related to storage at 40o F.

% Composition
Peak Compound Initial 3 Mos. 6 Mos. 9 Mos. 12 Mos.


1
2
3
4
5
6
7
8
9
10
11
12
S 13
oo 14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30


?
7
a-pinene
?
?
p-myrcene
7
7
?7
?7

heptanal
?
d-limonene
octanal
methyl heptenone
nonanal
methyl heptenol
octyl acetate
decanal
linalool
octanol
linalyl acetate
nonyl acetate
undecanal
nonanol
geranyl acetate
decyl acetate
dodecanal
citral


0.03
0.03
0.12
0.52
0.20
0.81
0.23
0.09
0.17
0.06
0.61
1.33
1.02
1.25
16.00
1.22
5.86
0.36
4.41
24.24
2.32
3.45
0.96
5.77
7.45
1.68
2.52
1.03
3.45
0.65


0.07
0.02
0.11
0.22
0.16
0.78
0.23
0.11
0.16
0.16
0.47
1.01
0.76
0.96
17.56
1.34
5.37
0.42
3.94
26.99
1.79
2.24
0.94
3.99
9.09
1.03
1.97
0.67
3.64
0.63


0.03
0.02
0.02
0.14
0.11
0.30
0.25
0.06
0.14
0.19
0.22
1.45
0.25
0.82
15.05
1.39
5.80
0.48
3.97
25.11
0.84
2.18
1.10
5.20
8.26
1.21
1.48
0.50
3.92
0.45


0.02
0.01
0.01
0.18
0.04
0.29
0.14
0.11
0.16
0.07
0.11
1.37
0.29
1.01
15.34
1.37
6.00
0.53
3.98
26.69
0.57
2.31
1.13
5.66
7.34
1.35
1.62
0.77
3.81
0.43


0.07
0.02
0.05
0.07
0.03
0.33
0.08
0.10
0.10
0.20
0.07
1.05
0.07
0.03
16.27
1.46
4.74
0.59
3.75
26.21
0.00
2.24
0.99
5.99
8.82
1.42
5.15
1.02
3.54
0.28







terpinyl acetate
terpineol
carvone
?
neryl acetate
?7
?
nerol
?
?
?
geraniol
?


4.18
3.82
2.68
0.46
0.53
0.01
0.00
0.38
0.00
0.00
0.01
0.08
0.01


Trend index: (+) increasing peaks
(-) decreasing peaks


4.30
3.70
3.14
0.48
0.89
0.04
0.00
0.41
0.01
0.00
0.01
0.18
0.01


4.03
3.59
4.90
0.61
1.54
1.18
0.39
1.31
0.68
0.30
0.27
0.18
0.08


3.49
3.22
4.46
0.72
1.44
0.82
0.31
1.35
0.30
0.37
0.35
0.33
0.13


3.58
1.70
4.75
0.73
1.53
0.01
0.03
1.38
0.12
0.39
0.40
0.50
0.14











Table 31.-Change in composition of expressed Duncan grapefruit oil. as related to storage temperature for six months.
% Composition
Peak Compound Initial 0* F 40* F 60 F 80* F


1
2
3
4
5
6
7
8
9
10
11
12
13
oo 14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30


? 0.01 0.01 0.01 0.02 0.01
? trace trace 0.04 0.04 0.04
? 0.02 0.01 0.01 0.01 0.01
? 0.06 0.02 0.02 0.03 trace
- ? 0.06 0.05 0.02 0.04 0.01
? 0.08 0.04 0.08 0.11 0.04
? 0.04 0.06 0.03 0.05 0.05
? 0.03 0.03 0.01 0.02 0.06
a-pinene 0.28 0.18 0.15 0.23 0.15
- ? 0.07 0.11 0.05 0.02 0.02
- ? 0.02 0.04 0.02 0.02 0.02
p-myrcene 0.09 0.09 0.17 0.15 0.12
? 0.02 0.07 0.05 0.08 0.05
? 0.13 0.15 0.12 0.11 0.09
heptanal 1.06 0.56 0.90 0.80 0.70
d-limonene 0.47 0.41 0.48 0.50 0.38
octanal 14.17 11.71 14.07 13.59 12.22
+ methyl heptenone 0.75 0.93 0.95 1.07 1.22
nonanal 4.74 4.44 4.66 4.67 4.22
? 0.13 0.39 0.29 0.23 0.23
+ methyl heptenol 0.22 0.29 0.33 0.54 0.59
octyl acetate 6.02 5.07 5.75 6.12 6.04
decanal 25.49 23.54 23.78 25.45 28.65
- linalool 1.77 1.75 1.52 1.38 0.00
octyl alcohol 2.66 3.46 3.14 3.02 2.81
linalyl acetate 0.97 1.32 1.14 0.99 0.82
- nonyl acetate 5.80 5.61 5.42 4.97 4.98
undecanal 6.33 6.44 7.23 6.43 6.33
nonanol 1.51 1.71 0.76 1.22 0.76
geranyl acetate 1.52 1.95 1.70 1.97 1.70










31 decyl acetate
32 dodecanal
33 citral
34 terpinyl acetate
35 terpineol
36 ?
37 carvone
38 ?
39 + neryl acetate
40 + nerol
41 ?
42 + ?
43 + geraniol
Trend index: (+) increasing peaks
(-) decreasing peaks


2.09
5.63
1.06
7.27
5.56
1.48
2.20
0.98
0.79
1.10
0.67
0.39
0.34


1.61
5.05
0.76
6.18
4.97
1.09
1.74
0.90
0.82
1.39
0.19
0.50
0.92


1.41
5.41
0.56
7.05
4.84
0.82
1.85
1.04
1.06
1.69
0.23
0.73
1.03







Chemical Composition of Grapefruit Oil.-Grapefruit oils
have been extensively analyzed (16, 17, 41, 42, 62, 64, 67, 69, 78,
108, 109) by improved electronic devices to detect the more
subtle flavor components, as shown in Table 32. More than 100
different components have been detected in coldpressed grape-
fruit oil; but, to date, only 80 have been definitely identified.

Table 32.-Chemical composition of coldpressed grapefruit oil.
TERPENES: ACIDS: ESTERS:
a-pinene acetic acid octyl acetate
sabinene caprylic acid linalyl acetate
p-myrcene capric acid nonyl acetate
d-limorlene geranyl acetate
*y-a-terpinene decyl acetate
p-ocimene ALCOHOLS: neryl acetate
a-p-cubebene methyl heptenol citronellyl acetate
a-p-copaene linalool geanyl butyrate
b-elemene octanol
carophyllene nonanol OXIDES:
? decanol trans-linalool oxide
a,p-humulene a-terpineol cis-linalool oxide
cadinene nerol
? geraniol COUMARINS &
A-cadinene nerolidol PSORALENS:
C15H24 elemol bergamottin
auraptene tranc.9---n.menthadiene-1- nl 7-geranvloxvcoumarin


ALDEHYDES:
heptanal
octanal
nonanal
citronellal
decanal
undecanal
dodecanal
citral ( neraal



PHENOLS:
o-phenylphenol


cis-2-8-p-menthadiene-l-ol
citronellol
trans-carveol
cis-carveol
dodecanol
l-8-p-menthadiene-9-ol
8-p-menthene-1,2-diol


TRITERPENOIDS:
b-sitosterol
citrostadienol
campesterol
stigmasterol
cycloartenol
24-methylene
cycloartenol
24-methylene lophenol


osthol
limettin (citroptene)
bergapten
bergaptol
7-methoxy-8-(2-formyl-2-
methylpropyl)-coumarin
7-((6,7-dihydroxy-3,7-
dimethyl-2-octenyl)oxy)-
coumarin
5-((3,6-dimethyl-6-
formyl-2-heptenyl)oxy)-
psoralen
Umbelliferone

KETONES:
nootkatone
methyl heptenone
carvone


Distilled Oil of Grapefruit

In Table 33, maximum and minimum values are included
for nine samples of vacuum steam distilled oil obtained in the
deoiling of grapefruit juice. It is interesting to note that, when
compared with the coldpressed oils, the distilled oils are much
higher in aldehyde content. Distilled grapefruit oils from juice
will generally run 90% higher in aldehydes and 60% lower in
esters than the expressed oils.








Table 33.-Maximum and minimum values for the physical and chemi-
cal properties of distilled grapefruit oil.
Property Maximum Minimum
Specific gravity 25*C/25*C 0.8539 0.8415
20
Refractive index T1 2 1.4746 1.4714

Optical rotation a 25 +96.50 +91.50
D
Aldehyde content, % 4.06 2.30
Ester content, % 2.52 0.08
Evaporation residue, % 3.66 0.19


Coldpressed Oil of 'Shaddock'
A sample of expressed oil was made from the true 'Shad-
dock' and the constants were determined as follows:

Sp. grave. 250C/250C 0.858
20
Ref. ind. D 1.4779


25
Opt. rot. a +81.14
D
Aldehyde content % 0.46
Ester content % 4.22
Evap. res. % 12.99

Both the aldehyde content and optical rotation are considerably
lower than those of grapefruit oil. The authors have not found
in the literature any data relative to pure oil of 'Shaddock', and
it is recommended that the synonym be eliminated, since oil
of 'Shaddock' might at some future time become an article of
commerce.

OIL OF 'PERSIAN' SEEDLESS LIME
The complete utilization of the peel from 'Persian' or 'Ta-
hiti' limes (Citrus aurantifolia Swingle) canned in Florida in-
volves the recovery of expressed and distilled oils. The 'Persian'
or seedless lime, which represents the bulk of the present com-
mercial crop in Florida, should not be confused with the 'Key'
or seedy lime produced in the southern part of the state. The









'Persian' lime is approximately twice the size of the 'Key' (or
'West Indian') lime. Today, most of the limes grown in Florida
are sold on the fresh fruit market. However, surplus and cull
fruit are available for juice and oil recovery. Cull fruit is of
good quality but unsuitable for shipment as fresh fruit because
of size and grade restrictions.
The primary products resulting from processing of this fruit
are single-strength and concentrated juice. The oil found in the
peel of the fruit is the first product recovered from the cannery
refuse, and both coldpressed and distilled lime oils are obtained.
The coldpressed oil is considered superior to the distilled oil
but, because of the relatively high price of the distilled oil, it
becomes economically feasible to recover both types of oil.
Lime oil was expressed with two different types of commer-
cial equipment in Florida during the 1948 season. These were
the Pipkin roll and Fraser-Brace extractor. Figure 26 shows
an installation for the manufacture of expressed and distilled
lime oil, and the flow diagram for this commercial process is
given in Figure 27.


Figure 26.-Installation for the manufacture of Florida expressed and dis-
tilled oil of lime.







































STEAM
JACKET


Figure 27.-Flow sheet for the manufacture of Florida expressed and dis-
tilled oil of lime.


A total of 26 samples of coldpressed and distilled 'Persian'
lime oils was obtained. Fifteen of the samples were coldpressed
oil secured from two plants, each of which used a different
method for the extraction of the oil from the peel. These sam-
ples were taken once a week from lots of oil which represented
the production for approximately one week. These samples rep-
resented coldpressed oil which was expressed from 11,232 stan-
dard field boxes of 'Persian' limes.
After the removal of some coldpressed oil from the peel, the
peel was then steam distilled to obtain the distilled lime oil.
Eleven distilled samples were secured and analyzed by methods
previously described.

85










Table 34.-Physical and chemical properties of coldpressed Persian lime oils in Florida during the 1948 season.
Refrac-
Refrac- tive Optical Aide- Evapo-
Type Specific tive Index Optical Rotation hyde Ester ration
Date of Gravity Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Extractor 20DC 20 Distillate ence 20 Distillate ence tent tent due
/200C D 20D 20 % % %
7- D Oa D (Citral)
7-15-48 Pipkin Roll 0.8810 1.4847 1.4730 0.0017 +40.60 +47.60 +7.00 5.52 7.98 13.36
7-24-48 Pipkin Roll 0.8798 1.4842 1.4730 0.0112 +41.00 +48.20 +7.20 4.86 7.42 12.95
8- 6-48 Pipkin Roll 0.8799 1.4845 1.4729 0.0116 +41.52 +49.24 +7.72 4.95 4.95 14.03
8- 9-48 Pipkin Roll 0.8823 1.4853 1.4731 0.0122 +41.80 +49.24 +7.44 5.35 8.13 13.44
8-13-48 Pipkin Roll 0.8816 1.4851 1.4730 0.0121 +39.76 +48.84 +9.08 3.66 8.08 14.67
8-20-48 Pipkin Roll 0.8821 1.4853 1.4730 0.0123 +38.60 +48.48 +9.88 5.19 8.03 13.97
9- 4-48 Pipkin Roll 0.8780 1.4839 1.4729 0.0110 +41.12 +48.72 +7.60 5.40 7.46 12.39
9-11-48 Pipkin Roll 0.8811 1.4846 1.4730 0.0116 +42.12 +49.92 +7.80 6.14 7.11 12.71
9-28-48 Pipkin Roll 0.8807 1.4847 1.4732 0.0115 +44.08 +52.20 +8.12 5.65 7.66 13.04
10- 4-48 Fraser-Brace 0.8792 1.4849 1.4732 0.0117 +54.60 4.46 7.28 13.23
10-13-48 Fraser-Brace 0.8786 1.4844 1.4734 0.0110 +51.80 5.20 7.11 12.62
10-16-48 Fraser-Brace 0.8796 1.4847 1.4725 0.0122 +50.52 5.17 6.78 13.04
10-23-48 Fraser-Brace 0.8789 1.4841 1.4724 0.0117 +49.32 4.74 7.02 13.24
10-16-48 Pipkin Roll 0.8777 1.4837 1.4731 0.0106 +43.36 +51.12 +7.76 5.50 6.80 11.88
10-23-48 Pipkin Roll 0.8769 1.4834 1.4731 0.0103 +43.00 +49.20 +6.20 5.83 7.15 11.01
Too dark to read in 25 mm tube.









Coldpressed Oil of Lime
The physical and chemical properties of samples of cold-
pressed lime oil, which were obtained from two commercial
plants from July through October 1948, are presented in Table
34. The factor found to influence the physical and chemical
properties of coldpressed 'Persian' lime oil to the greatest ex-
tent was the yield of oil secured from the fruit.
Yield data on the two methods of manufacture were deter-
mined and are as follows: (1) Pipkin roll 0.4 pound of oil per
ton of fruit and (2) Fraser-Brace extractor 1.22 pounds of oil
per ton of fruit. The Fraser-Brace extractor obtained three
times more expressed oil than the Pipkin roll. Oil manufactured
by the Fraser-Brace extractor was so dark in color that optical


Table 35.-A comparison between the physical and chemical properties
of coldpressed Persian lime oil manufactured by two methods of extraction
(1948 season).

Method of Extraction
Property
Fraser- Pipkin Difference
Brace Roll

Yield of Oil/Ton of Fruit 1.22 lb. 0.40 Ib.

Specific gravity 20C/20C 0.8793 0.8773 0.0020

Refractive index 1t20 1.4844 1.4835 0.0009
Refractive index
Refractive index
of 10% distillate 20D 1.4724 1.4731 0.0007

Difference 0.0120 0.0104 0.0016

Optical rotation a 0 +43.18 -

Optical rotation
of 10% distillate a2D +49.94 +50.16 +0.24

Difference 6.98 -

Aldehyde content (citral), % 4.95 5.66 0.71

Ester content, % 6.90 6.98 0.08

Evaporation residue, % 13.14 11.44 1.70














Table 36.-Col

Property


Sp. gray. 200C/20C
Ref. ind. 7720
D
Ref. ind. 10% dist. r12
S Difference
oo 00
0 Opt. rot. a

Opt. rot. 10% dist. aD2
Difference
Aldehyde (citral), %
Ester content, %
Evap. res., %


mparison of commercial coldpressed 'Persian'
Pipkin roll (11)*
Max. Min.
0.8823 0.8769
1.4853 1.4834


1.4732
0.0122
+43.36

+52.20
+9.88
6.14
8.08
14.67


1.4729
0.0103
+38.60

+47.60
+6.20
3.66
4.95
11.01


lime oils made by three different processes.
Fraser-Brace (4) FMC in-line (15)
Max. Min. Max. Min.
0.8792 0.8786 0.8947 0.8533
1.4849 1.4841 1.4907 1.4744


1.4734
0.0122
**

+54.60
**
5.20
7.28
13.24


1.4724
0.0110
**

+49.32
**
4.46
6.78
12.62


1.4734
0.0177
+49.01

+51.71
+10.27
6.66


16.67


1.4730
0.0053
+39.85

+48.33
+689
4.30


11.50


* No. of samples.
*Too dark to read in 25 mm tube.







rotation determinations could not be made in a 25 mm tube. The
average values for two composite samples of oil made by each
of two processes from October 13 to 16 and October 20 to 23
from different lots of fruit are presented in Table 35.
Relation of Yield to Properties.-It can be seen from Table
35 that the higher the yield of oil obtained from the fruit, the
higher the value for specific gravity, refractive index, and
evaporation residue. As the yield of oil is increased, more high-
boiling, high-molecular-weight constituents are evidently ex-
tracted, and the presence of a larger percentage of these com-
pounds in the oil results in higher values for specific gravity,
refractive index, and evaporation residue.
The total quantity of recoverable oil in whole limes for this
season ranged between 0.20 and 0.22%. This value is on the
basis of 11,232 standard field boxes of limes.
Effect of Aqueous Phase on Aldehyde Content.-As shown
in Table 34, relatively small variations in composition of cold-
pressed 'Persian' lime oil were noted throughout the processing
season. As the season progressed, limes were continually be-
coming mature, resulting in a mixture of fully mature and par-
tially mature fruit. This factor probably accounts for the fact
that properties of the oil remained fairly constant. However,
the last two samples taken, representing the last 2 weeks' run
of the season, gave significant differences for specific gravity
and evaporation residue. In each case, these values were lower;
whereas, all the other values remained practically the same.
It was impossible to make a material balance on the aqueous
phase for each of the two processes because of irregularities in
processing operations. However, a significantly larger quantity
of water was used in the Fraser-Brace process than in the
Pipkin roll process. Data in Table 35 indicate that the aldehyde
content of oil produced by the Fraser-Brace process was lower
than that for the Pipkin roll process. This would indicate that
aldehyde content decreases as amount of aqueous phase which
comes in contact with the oil during processing is increased.
Comparison of Commercial 'Persian' Lime Oils Made by
Three Different Processes.-Data in Table 36 show that each
method used to extract the oil gives an oil that is slightly dif-
ferent in its overall physiochemical properties. The aroma and
flavor of the oils will differ slightly and therefore becomes an
important consideration in the selection of an oil for any given
use or purpose.








Chemical Composition of Lime Oil. -Many investigators (26,
27, 41, 98, 103, 104) have worked on the isolation and identifi-
cation of the flavor components in coldpressed 'Persian' lime oil.
Approximately 100 different flavor constituents have been found
in the coldpressed oil, but only 50 have been positively identified,
as shown in Table 37.

Comparison of Florida Coldpressed 'Persian' Lime Oil with
Coldpressed 'West Indian' Lime Oil.-Florida coldpressed 'Per-
sian' lime oil is compared with coldpressed 'West Indian' lime
oil in Table 38. These small seedy limes are known by various
names: 'Mexican', 'Dominican', and 'Key' limes. The values
shown in the table for 'West Indian' lime are those given by
Guenther (26). These data show that the two oils are quite
different. 'Persian' lime oil generally has a higher value for
optical rotation and a slightly lower value for aldehyde content
than those for 'West Indian' lime oil. Since these two types of


Table 37.-Chemical composition of coldpressed 'Persian' lime oil.

TERPENES: ALCOHOLS: PHENOLS:
a-pinene octanol 1,4-cineole
p/-pinene nonanol 1,8-cineole
/-myrcene a-terpineol
d-limonene linalool
y-terpinene p-terpineol
p-cymene borneol
camphene geraniol
terpinolene bergaptol
tetradecane decanol
A-elemene
C15H4 OXIDE: ESTERS:
pentadecane
C1jH2, (2) monoterpene- Methyl anthranilate
a-bergamotene oxides C1oHO70
caryophyllene
a-elemene ALDEHYDES: ACIDS:
Ci5H24
a,p-humulene nonanal acetic
C15H24 decanal octylic
p-bisabolene dodecanal decylic
Cneral
C15H24 citral eranial
CI5H24 geranial

COUMARINS:
5,7-dimethoxy coumarin (limettin)
5,8-dimethoxyfurano-2',3',6,7-coumarin (isopimpinellin)
7-methoxy-5-geranoxy coumarin
5-hydroxy-7-methoxy coumarin
4,6-dimethoxy-2-geranoxycinnamic acid
5,-Hydroxyfurano-2',3',6,7-coumarin (Bergaptol)








Table 38.-Florida coldpressed 'Persian' lime oil compared with cold-
pressed 'West Indian' lime oil.

Property 'Persian' Lime* 'West Indian' Lime
Max. Min. Max. Min.
Specific gravity 0.8947 0.8533 0.886 0.878
20 C/20 C (15" C) (15 C)
Refractive Index
20 C t72 1.4907 1.4744 1.4860 1.4800

Optical Rotation
S20 +49.01- +38.60 +40 +35

Aldehyde (control), % 6.66 3.66 8.5 4.5

Ester Content, % 8.08 4.95 -

Evap. Res., % 16.67 11.01 13.5 10.0
*All methods.

oil represent two distinct varieties of lime, a fair comparison of
their qualities cannot be made.

Distilled Oil of Lime

The properties of steam-distilled 'Persian' lime oil are given
in Table 39. These samples were obtained from peel which was
first expressed to obtain some coldpressed oil, and subsequently
steam-distilled to produce the distilled oil of lime. In Table 40,
a comparison is given of two samples of distilled 'Persian' lime
oil made from the same lot of fruit. One sample was made by
the Pipkin roll process, while the other was made by the Fraser-

Table 39.-Physical and chemical properties of distilled Persian lime oils
produced in Florida during the 1948 season.
Specific Refractive Optical Aldehyde Ester Evapo-
Gravity Index Rotation Content Content ration
Date 20*C 4 20 o20 % % Residue
/20C D D (Citral) %
7-31-48 0.8556 1.4745 +50.52 1.61 2.41 0.18
8- 6-48 0.8579 1.4751 +46.84 2.32 3.49 0.88
8- 9-48 0.8562 1.4746 +47.24 2.71 3.10 0.42
8-13-48 0.8572 1.4749 +47.44 1.77 3.04 1.23
8-20-48 0.8561 1.4743 +48.08 1.76 2.54 0.29
9- 4-48 0.8560 1.4748 +48.92 2.31 2.63 0.48
9-11-48 0.8569 1.4748 +48.92 2.27 2.24 1.17
9-28-48 0.8596 1.4757 +47.60 2.37 2.49 1.70
10-15-48 0.8546 1.4747 +52.60 4.58 1.75 0.25
10-16-48 0.8565 1.4749 +49.60 2.27 2.38 0.83
10-23-48 0.8555 1.4749 +50.00 2.34 2.15 0.70







Brace process. In the Pipkin roll process the peel, after passing
through the Pipkin roll, is crushed and mashed in an Enterprise
meat chopper; water is added, and the oil is then distilled. In
the Fraser-Brace process, the effluent from the centrifuge is
distilled to obtain the oil.
From Table 40 it can be seen that there is a considerable
difference in these two oils. The oil obtained from the Fraser-
Brace process had a lower value for specific gravity and a higher
value for optical rotation. The aldehyde- content was 101%
higher. The ester content and the evaporation residue were 36
and 232% higher, respectively, for the Pipkin roll process. The
loss of aldehydes which occurred in the Pipkin roll process was
considered to be due to the degradation of the aldehydes by
steam in the presence of citric acid. The still charge in the
Pipkin roll process was much more acidic than that in the
Fraser-Brace process. Guenther (27) has shown that the com-
bination of heat and acid on lime oil has a marked effect on the
aldehyde content of the oil.
Effect of Coldpressing the Peel Prior to Distillation.-In
Table 41, a comparison is made of the physical and chemical
properties of oils distilled from fruit that had been coldpressed
and from fruit that had not been coldpressed. Each of these
samples was prepared by the Pipkin roll process.
As can be seen from the data in Table 41, there are no
significant differences in the values for specific gravity, refrac-
tive index, optical rotation, and aldehyde content. However, the

Table 40.-A comparison of two samples of distilled Persian lime oil
made by two processes.
Process
Property Fraser-Brace Pipkin Roll Difference

Specific gravity 20OC/20"C 0.8546 0.8565 0.0019

Refractive index 720 1.4747 1.4749 0.0002

Optical rotation (20 +52.60 +49.60 +3.00

Aldehyde content (citral), % 4.58 2.27 2.31

Ester content, % 1.75 2.38 0.63

Evaporation residue, % 0.25 0.83 0.58








Table 41.-Distilled Persian lime oil made from peel which was cold-
pressed prior to distillation as compared with oil made from peel which was
not coldpressed prior to distillation.

Peel Was Peel Was not
Coldpressed Coldpressed
Property Prior to Prior to Difference
Distillation Distillation

Specific gravity 20oC/20C 0.8569 0.8560 0.0009

Refractive index r2D 1.4748 1.4748 0.0000

Optical rotation 20 +48.92 +48.92 0.00

Aldehyde content (citral), % 2.27 2.31 0.04

Ester content, % 2.24 2.63 0.39

Evaporation residue, % 0.48 1.17 0.69


oil made from peel that had not been coldpressed
values for ester content and evaporation residue.


had higher


Comparison of Florida Distilled 'Persian' Lime Oil with Dis-
tilled 'West Indian' Lime Oil.-Table 41 gives a comparison of
Florida distilled 'Persian' lime oil with distilled 'West Indian'
lime oil. The physical and chemical properties shown in the
table for 'West Indian' lime oil are those given by Guenther (26)


Table 42.-Florida distilled 'Persian'
'West Indian' lime oil.


lime oil compared with distilled


Persian Lime West Indian Lime
Property Maximum Minimum Average Maximum Minimum
Specific gravity
(20C/20C) 0.860 0.853 0.857 0.868 0.862
Refractive index (15C) (15C)
(20C) 1.4757 1.4743 1.4749 1.4770 1.4750
+52.60 +46.84 +48.91
Optical rotation (20C) (20C) (20C) +46 +35
Aldehyde con-
tent, % 4.6 0.72 2.4 1.5 0.5
(as citral)
Ester
content, % 3.5 1.8 2.6 -
Evaporation
residue, % 1.7 0.3 0.7 -








It will be noted that the 'Persian' lime oil produced in Florida
has higher values for optical rotation and aldehyde content;
whereas, the values for specific gravity and refractive index
are lower than those of the 'West Indian' lime oil.
Guenther (26) states that a high grade lime oil should have
a specific gravity of not less than 0.864 at 150 C. It can be seen
from the data in Table 42 that the 'Persian' lime oil produced
in Florida is quite different from the 'West Indian' lime oil and
cannot be expected to meet the same requirements, since it is
made from a different variety of lime. The maximum and mini-
mum values for Florida lime oil as given in Table 41 are con-
sidered to represent a high quality distilled 'Persian' lime oil.
Since these two types of oil are made from two distinct varieties
of limes, they probably should have different quality standards.

OIL OF LEMON
According to Knorr (73), Florida is today the largest citrus-
growing area in the world. Yet, oddly enough it has long been
dependent on California for its lemons. Florida's average con-
sumption of California lemons over the past 10 years has
amounted to 160,300 boxes annually. However, this failure to
produce lemons sufficient to meet its own needs has not always
been true of Florida. In the years before the Great Freeze of
1894-95, Florida supplied not only its own population but shipped
as many as 140,000 boxes of lemons per season-roughly 5%'
of the citrus then moving out of the state.
But with the Great Freeze, the production of lemons in
Florida came to a stop. Most of the lemon groves, then lying
north of where citrus is grown today, were killed by the cold,
and Florida lemons disappeared from the nation's tables-both
dinner and statistical.
It is true that lemons are more tropical in their temperature
requirements than oranges, grapefruits, and tangerines-but the
Great Freeze cannot solely be blamed for the disappearance of
Florida's lemon industry. If cold had been the only limiting
factor, lemon growers could have moved south and prospered
along with the rest of the industry. The Freeze simply triggered
a gun that had already been aimed before the Freeze of 1894.
Florida's lemon industry was being menaced by competition from
California. It is axiomatic among lemon growers and shippers
that the best lemons came from areas that are hot and dry, for
only in such areas is there freedom from the fruit-blemishing








scab fungus, and sufficient absence of humidity to facilitate the
curing that is so essential for prolonged storage, shipment, and
shelf-life. The pessimism among Florida lemon growers that
followed the Freeze of 1894 was well expressed by Hume many
years ago: "In the growing of lemons there is always a double
problem; first, the production of high-grade fruit, and then
the coloring and curing of it for market. It is questionable
whether lemon growing will ever become a stable and profitable
industry in any citrus region where scab is prevalent and where
the harvesting and curing season is moist."
Florida's recent comeback as the world's leading citrus pro-
ducer was made possible through a technological advance-the
manufacture of frozen concentrated citrus juice. Coupled with
Florida's low growing costs, the stimulus provided by the con-
centrate process has been so great that today Florida sends to
market as frozen orange concentrate more oranges than were
grown in the state the year this product was first introduced.
With respect to lemons, it is this same technological advance
-frozen concentrate-that bids fair to resurrect Florida's old-
time lemon industry. Already approximately 8,000 acres of
lemons have been planted to help supply the nation's demand for
frozen lemonade concentrate. With this revolution in the use
of lemons, old arguments against Florida-grown lemons lose
their pertinence. Commercial juice extractors, without the
housewife's picky concern over external appearances, do not
cast out fruits blemished by scab, nor are processors worried
about keeping quality of fruits that are juiced upon picking.
With scab and keeping quality no longer limiting considerations,
efforts can now be directed toward producing lemons that are
superior in acid production and quality of peel oil. An advantage
can be taken of what once used to be a source of embarrassment
in the fresh-fruit market-the overlarge size of Florida's lemons.

Coldpressed Oil of Lemon
Physicochemical Properties of Coldpressed Lemon Oil from
42 Lemon Selections.-In 1958 Knorr (73) made a search for
varieties of lemons that would supply the highest yield of acid
per acre and a high quality peel oil in good yield, with desirable
tree characteristics such as longevity, freedom from disease, and
high yield of fruit. Never before had lemons been selected for
these characteristics.
The physicochemical properties of coldpressed lemon oils









Table 43.-The physicochemical properties of coldpressed lemon oil. (From 40 lemon selections.)
Refrac- Optical
Refrac- tive Opti- Rotation
Specific tive Index cal of 10% Aide- Evapo- U. V. Spectrum
Selection Gravity Index of 10% Differ- Rota- Distil- Differ- hyde rative 315 mp log E 0.25 g
25C/25C 77 20 Distil- ence tion late ence Con- Residue 100 cc
No. Name D late a 25 25 tent %
T20 D D
CD Peak M
CD Peak My


1. Avon Commercial
2. Perkin
3. Harvey #3
4. Avon #3
5. Cowgill #2
6. Avon #1
7. Harvey #1
8. Bearss #1
9. Avon #2
10. Harvey #2


0.849 1.4744 1.4729 0.0015 +63.18 +59.58 -3.60 2.31 2.6
0.850 1.4745 1.4729 0.0016 +63.22 +60.22 -3.00 2.13 2.4
0.850 1.4743 1.4729 0.0014 +62.67 +59.27 -3.40 2.32 2.0
0.849 1.4742 1.4729 0.0013 +63.91 +61.31 -2.60 2.31 2.1
0.849 1.4743 1.4729 0.0014 +62.62 +60.22 -2.40 2.68 2.2
0.850 1.4742 1.4730 0.0012 +62.07 +58.38 -3.69 2.54 2.0
0.849 1.4741 1.4730 0.0011 +60.67 +58.58 -2.09 2.81 1.9
0.850 1.4742 1.4731 0.0011 +60.98 +58.82 -2.16 3.45 1.9
0.850 1.4743 1.4731 0.0012 +61.98 +58.82 -3.16 2.63 2.1
0.850 1.4742 1.4729 0.0013 +60.85 +59.22 -1.63 2.90 2.0


11. Bearss #2 0.850 1.4741 1.4729 0.0012 +60.58 +56.98 -3.60 3.08 2.0
12. Hogsette 0.849 1.4740 1.4729 0.0011 +62.02 +58.42 -3.60 2.27 1.9
13. Carney 0.849 1.4740 1.4728 0.0012 +66.07 +63.67 -2.40 2.73 2.0
14. Moreland 0.849 1.4740 1.4729 0.0011 +63.51 +60.51 -3.00 2.45 1.9
15. Schultz 0.849 1.4740 1.4728 0.0012 +64.58 +60.18 -4.40 2.28 2.0
16. Edwards 0.849 1.4740 1.4729 0.0011 +63.58 +59.98 -3.60 2.27 2.0
17. Lisbon (USDA) 0.848 1.4740 1.4728 0.0012 +63.82 +60.02 -3.80 2.72 2.0
18. Eureka (USDA) 0.848 1.4740 1.4728 0.0012 +64.87 +62.07 -2.80 1.99 2.1
19. Corregia 0.849 1.4740 1.4728 0.0012 +63.91 +60.51 -3.40 2.45 2.1
20. Cowgill #1 (USDA) 0.849 1.4740 1.4728 0.0012 +62.80 +59.80 -3.00 2.45 1.9
21. Des 4 Saisons (USDA) 0.849 1.4739 1.4728 0.0011 +63.65 +60.45 -3.20 2.99 1.8
22. Mexican (USDA) 0.848 1.4739 1.4728 0.0011 +65.22 +62.42 -2.80 2.27 1.7
23. Bernia (USDA) 0.849 1.4740 1.4729 0.0011 +57.82 +55.42 -2.40 2.17 1.9
24. Kusner (USDA) 0.848 1.4739 1.4728 0.0011 +65.20 +63.00 -2.20 2.45 1.9
25. Sturrock 0.848 1.4743 1.4725 0.0018 +68.98 +74.78 +5.80 3.00 3.0


0.43 0.94 312.5
0.47 0.96 312
0.40 0.84 315
0.41 0.82 315
0.48 0.92 315
0.42 0.86 312.5
0.35 0.74 315
0.44 0.86 315
0.46 0.89 315
0.39 0.82 315
0.38 0.83 315
0.28 0.66 315
0.23 0.72 315
0.33 0.72 315
0.32 0.74 315
0.36 0.75 315
0.31 0.68 315
0.37 0.76 315
0.34 0.72 315
0.35 0.73 315
0.33 0.72 315
0.22 0.52 315
0.28 0.67 315
0.34 0.74 315
0.25 0.66 315


---




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