The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
Technical Bulletin 677 June 1964
Rudolph Hendricksori James Kesterson
J. R. Beckenbach, Director
" / " -
INTRODUCTION .. ................... ...... ................................ 3
PROCESSING TECHNIQUE AND ANALYSES ................................................ 4
PRODUCTION PROBLEMS ...................... .. ...................................... 8
Clarification of Press Liquor ..-........................... ..... .................... 8
Scale -------................ ..... .. ................... ..... ........... .......... 11
Foam ing ............................................. ............. .............. 14
Storage ,Changes -- --............................ ......................... 18-
UTILIZATION ........ .... ..................................... .......................... 22
Feeding Value ................---- ..................................... .......... 22
Other U ses .............--------........................................................ 24
SUM MARY ......................... ......................................................... ..... 24
ACKNOWLEDGMENTS ---- ---.............. .......... ....................... -----...... 25
LITERATURE CITED ............ .................................................... .............. 25
R. HENDRICKSON AND J. W. KESTERSON 1
Citrus molasses, a by-product from processed citrus peel
residue, became commercially important in Florida during the
1941-42 season. As shown in Table 1, the tonnage increased
rapidly in the next few years and has remained reasonably con-
stant since 1946-47 despite the increasing quantity of processed
fruit. The retrogressively lower yields of molasses since 1946-47
were caused by a 25 percent increase in citrus juice yields (23)2,
an unknown quantity of molasses utilized in pelletizing dried
citrus pulp fines, and an economic preference of some citrus proc-
essors to manufacture only dried citrus pulp from citrus peel
Molasses is made from citrus by curing waste residue with
small quantities of lime, after which continuous presses expell
a press liquor or juice that is concentrated to a syrup. Approxi-
mately 0.15 to 0.30 percent calcium hydroxide is required to
react with the chopped citrus residue to facilitate the release
of bound juices. The expelled press liquor contains 9 to 15
percent soluble solids, of which from 60 to 75 percent are sug-
ars. Without further processing this liquor has a biological
oxygen demand of between 40,000 and 100,000 ppm (25) and
can create a waste disposal problem if pumped into the ground
or dumped into lakes or streams. By concentrating this straw-
colored, bitter liquid in multiple-effect evaporators, a viscous
dark brown molasses is obtained that is readily accepted when
fed to cattle. The final product, as now manufactured in Florida,
is required to meet the following minimum state standards: it
must contain 45 percent total sugars expressed as invert sugar,
and test not less than 35.5 Brix by double dilution (8).
This bulletin has been prepared to assist those in the citrus
industry who are faced with the daily problems of citrus molas-
ses manufacture and to inform potential users as to its known
physical, chemical, and feeding characteristics.
1Associate Chemist and Chemist, Citrus Experiment Station, Lake
2 Figures in parentheses refer to Literature Cited.
4 Florida Agricultural Experiment Stations
TABLE 1.-NUMBER OF BOXES OF CITRUS PROCESSED AND CORRESPONDING
PRODUCTION OF CITRUS MOLASSES AT FIVE-YEAR INTERVALS (5).
Citrus Processed Citrus Molasses
Season (1,000 Boxes) Production (Tons)
1941-42 14,400 2,500
1946-47 36,700 58,000
1951-52 61,700 54,000
1956-57 88,300 59,800
1961-62 109,700 54,800
PROCESSING TECHNIQUE AND ANALYSES
The problem of manufacturing citrus molasses would seem-
ingly involve only that of concentrating expelled citrus press
liquor. The simplicity of this procedure, however, is complicated
by the variable nature of the dilute liquor expressed from the
different varieties of citrus, and further by processing variables
such as quantity of lime added, bin storage time, etc. Press
liquor will also include, at times, quantities of a more dilute
peel-oil-recovery effluent which would otherwise be difficult to
dispose of by customary sanitation procedures. In Table 2 are
shown maximum, minimum, and seasonal average analyses of
press liquor from one processing plant (27). The extent to
which the press liquors of Table 2 have been diluted by less
concentrated effluents in normal plant operation can be estimated
TABLE 2.-APPROXIMATE COMPOSITION OF PRESS LIQUOR FROM A CITRUS
PROCESSING PLANT (27).
Constituent Maximum Minimum Average
pH 6.4 5.4 5.7
Brix at 17.5 C 12.6 6.1 10.1
Total solids, % 11.61 5.64 8.93
Volatile matter, % 94.36 88.39 91.07
Sucrose, % 3.09 1.20 2.40
Reducing sugars, % 5.81 2.82 4.23
Total sugars, % 8.58 4.08 6.63
Protein (N X 6.25), % 0.59 0.40 0.47
Pectin (alcohol ppt.), % 0.88 0.27 0.66
Pentosans, % 0.42 0.23 0.31
Ash, % 0.94 0.43 0.72
Fixed acid, as citric, % 0.30 0.15 0.21
Volatile acid, as acetic, % '0.78 0.01 0.14
Alcohol, % by vol. 0.39 0.00 0.22
Peel oil, % by vol. 0.58 0.12 0.23
Citrus Molasses 5
by comparing the Brix values in this table with those of labora-
tory prepared press liquor from different citrus varieties, as
shown in Table 3. There were approximately 15 percent more
soluble solids in the peel juices than in the fruit juices of the
TABLE 3.-COMPARISON OF FRUIT JUICE BRIX AND PRESS LIQUOR BRIX OF
THE SAME FRUIT.
No. of Fruit Juice Press Liquor
Citrus Variety Samples Average Brix Average Brix
Hamlin 9 11.2 12.3
Pineapple 3 13.0 14.3
Valencia 8 11.9 13.8
Marsh 5 9.2 11.0
Duncan 4 10.7 13.3
The conversion of the released citrus press liquor to citrus
molasses begins usually by passing it over a vibrating screen
(40 to 80 mesh) to eliminate the larger particles. The liquor is
held temporarily in a storage tank until it can be pasteurized
through heat exchangers that flash the liquid under pressure
from 2400 F to atmospheric conditions. This operation serves
four purposes: peel oil is distilled off and recovered as an addi-
tional by-product, the high temperature kills all spoilage organ-
isms, calcium citrate and other calcium salts with inverted solu-
bility are precipitated, and the flocculation and sedimentation
of other suspended matter are aided. Some processors at this
point partially clarify the liquor prior to its entering the evap-
orator by settling out suspended matter in the hot press liquor
storage tank. Multiple-effect evaporators, schematically shown
in Fig. 1, are used in concentrating the hot liquor to 500 Brix,
whereupon it is usually screened (40 mesh)3 to eliminate the
larger scale particles that may have loosened in the evaporator.
A forced circulation finishing pan completes the concentration
to 72 Brix.
A spray evaporator has been used in a few instances to con-
centrate citrus press liquor with hot flue gases. Concentrating
is continued in a second effect, that uses the latent heat of
vaporization of the first effect, and completed in the usual fin-
ishing pan. In this arrangement, stripper oil is not recovered
3 All mesh sizes refer to U. S. Bureau of Standards sieve numbers.
6 Florida Agricultural Experiment Stations
and molasses stability is said to have suffered, presumably by
virtue of the low processing temperatures.
850 G.PM. W after
l221' 173 115' 145*
g; O 1_
Fig. 1.-Flow and material balance for a four-body
The average costs of processing, warehousing, and selling
citrus molasses and other citrus by-products have been published
recently by Spurlock and Hamilton (35).
A typical analysis of citrus molasses compiled from pub-
lished (11, 16, 22) and unpublished data is shown in Table 4.
TABLE 4.-TYPICAL ANALYSIS OF FLORIDA CITRUS MOLASSES.
Brix ..................------ ........-----... 72.0 Potassium (K) % ................. 1.1
Sucrose % ..--. ...................-........ 20.5 Calcium (Ca) % ...-..........- .. 0.8
Reducing sugars % .-...........-- 23.5 Sodium (Na) % ----............- ... 0.3
Total sugars % ....----------..... 45.0 Magnesium (Mg) c% ............ 0.1
Moisture % ...............--- ---.. ..- .... 29.0 Iron (Fe) % ........ .......... 0.04
Protein (N X 6.25) % ........---.. 4.1 Phosphorus (P) % .................. 0.06
Nitrogen-free extract % ..-.... 62.0 Manganese (Mn) -......-...... 0.002
Fat % ......- -........... .... ......... ... ... 0.2 Copper (Cu) % ...--............. 0.003
Fibre % ...........-.............- ......... 0.0 Silica (SiO) % .-................... 0.04
Ash % ....-...............- .......... ......... 4.7 Sulphur (S) % .........-........ -. 0.17
Glucosides % ........................... 3.0 Boron (B) % ...-..- ... ..... ....----. 0.0006
Pentosans %- ............................-.. 1.6 Niacin (ppm ) ...-.......--.... ........ 35
Pectin %0 ........-- .......................-- .. 1.0 Riboflavin (ppm) --......... --........ 11
Volatile acids % ...................... 0.04 Pantothenic acid (ppm) ....... 10
pH .................--- ............--....... 5.0 Viscosity 25* C (centipoises) 2000
In this table the ash constituents are shown in considerable
detail. A comparison between citrus molasses and blackstrap
molasses is found in Table 5. Blackstrap molasses has a much
Citrus Molasses 7
TABLE 5.-COMPARATIVE DATA ON CITRUS AND BLACKSTRAP MOLASSES.
Citrus Molasses Blackstrap (9)
Analysis Commercial* Laboratory** Louisiana Cuban
Brix 72.0 73.1 90.7 87.2
Sucrose % 19.6 26.1 30.1 37.3
Reducing sugars % 22.9 24.9 26.4 16.6
Total sugars % 43.5 52.4 58.0 55.8
Ash, carbonate % 4.7 3.0 10.8 10.9
Protein (N X 6.25) % 4.1 3.6 1.6 2.1
pH 5.0 5.9 5.7 5.5
Average of 36 samples
** Average of 16 samples
TABLE 6.-CITRUS MOLASSES PREPARED FROM PEEL OF DIFFERENT Citrus
Total Brix Viscosity
Type of Invert Sugar (Refrac- Ash 300 C Apparent*
Citrus Sugar As Invert tometer) Content Centi- Purity
Peel % % 28 C % poises %
Marsh 14.6 44.5 70.3 4.09 186 63.3
Marsh 17.0 48.9' 76.5 3.43 880 63.9
Marsh 17.6 51.3 78.4 4.39 1660 65.4
Marsh 16.6 46.8 73.0 3.26 265 64.1
Avg. 16.4 47.9 72.5 3.79 748 64.2
Duncan 22.7 51.4 70.7 2.72 180 72.7
Duncan 22.9 50.6 71.9 2.38 194 70.4
Duncan 25.2 56.1 77.7 2.76 905 72.2
Avg. 23.6 52.7 73.4 2.62 430 71.8
Pineapple 30.9 52.0 69.7 3.03 129 74.6
Pineapple 32.0 51.2 69.8 2.60 150 73.3
Pineapple 33.7 53.9 73.6 3.03 420 73.2
Avg. 32.2 52.4 71.0 2.89 233 73.7
Hamlin 25.7 55.5 74.2 2.89 510 74.7
Hamlin 27.3 54.3 73.9 2.91 820 73.5
Hamlin 29.3 55.9 73.9 2.40 ...... 75.6
Hamlin 31.0 57.3 73.3 2.36 360 78.2
Avg. 28.3 55.7 73.8 2.64 563 75.4
Valencia 32.0 55.8 72.9 2.52 295 76.5
Valencia 19.4 52.7 70.2 3.11 345 75.1
Avg. 25.7 54.2 71.5 2.81 320 75.8
Apparent purity refers to proportional percentage of soluble solids found to be sugars
by chemical analysis.
8 Florida Agricultural Experiment Stations
higher ash content and a lower protein content, and has been
concentrated to a greater degree than molasses. The difference
in percentage of sugars reflects only that blackstrap has been
concentrated to a greater degree. Standards for citrus molasses
have been established at a lower level of concentration to avoid
a viscosity problem that is aggravated by the increased quan-
tity of insoluble suspended material formed during its conversion
A measure of the differences that can be expected when
citrus molasses is manufactured carefully in the laboratory from
the peel of different Citrus varieties is shown in Table 6. The
press liquor was filtered sparkling clear prior to its conversion,
and the partially concentrated product was decanted from insolu-
ble scale to produce a final molasses that in each case would repre-
sent the ultimate attainable in full-scale production. The orange
samples had a greater proportion of sugars present than the
grapefruit samples. Ash content and viscosity were so greatly
improved that clarification seemed necessary to the general
Clarification of Press Liquor
The need for citrus molasses to have a reasonably low vis-
cosity has been shown previously (13, 14) and will be expanded
upon further. One of the many procedures for accomplishing
this task has been the unique method practiced in one Texas
plant (31). In this installation the citrus press liquor is con-
centrated in two stages with submerged combustion burners
that burn a balanced composition of air and natural gas. Besides
the elimination of the severe scaling that would occur upon the
heat exchange tubes, the submerged burners immediately neu-
tralize any excess lime, automatically adjust the pH to about
6.0, and aid in the precipitation of the calcium salts which can
then be eliminated in a continuous settler.
Other alternate procedures for clarification that have been in-
vestigated are filtration, screening, centrifugation, flotation, and
sedimentation. Filtration was disappointingly slower even when
filter-cel was used to body-treat and to pre-treat the filter sur-
face. In an unpublished pilot-plant test of an Oliver pre-coated
continuous filter with citrus press liquor, the best filtration
rate, 8 gallons per square foot per hour, occurred with the
Citrus Molasses 9
following parameters: 3 minutes per revolution, 0.003 inch cut,
24 pounds of Hyflo filter-eel per 1,000 gallons, and a press liquor
temperature of 1850 F. The results suggested this method to
It is the general practice of the industry to use vibrating
screens of approximately 40 mesh to eliminate the larger parti-
cles in press liquor not withheld by the continuous press. When
citrus press liquor was passed through a series of standard sieve
screens extending beyond 40 mesh down to 200 mesh, it was
found that the filtrate was still turbid and cloudy. Considerable
suspended matter was retained that was well distributed in
particle size. At higher temperatures where particle size is
increased by agglomeration, the screen motion necessary for
filtration was sufficient to break the flocs.
Since press liquor has varying proportions of suspended mat-
ter that both sink and rise, a centrifuge was not able to separate
an adequately high clarity liquor. However, by the addition of
a low density immiscible liquid, such as d-limonene, benzene, or
toluene, an effective flotation of suspended solids could be
The most advisable method for economically producing a
more clarified press liquor nevertheless would seem to be sedi-
mentation. Under the microscope, press liquor appears as a
liquid with a flocculent white precipitate. Throughout the
liquid are distributed minute oil droplets of varying sizes, so
small and scattered as to be physically dispersed in the sus-
pended particle. By removing the peel oil, either by distillation
or flashing, the buoyed particle is allowed to settle. The effec-
tiveness of partial distillation of press liquor upon the settling
rate of suspended matter is shown in Fig. 2. It may be noted
that as distillation proceeds a greater proportion of peel oil is
removed, thereby improving settling rate of suspended matter.
When press liquor is boiled with an excess of peel oil at approxi-
mately atmospheric pressures, water and oil will distill over in
a ratio of approximately 2 parts water and 1 part oil. At lower
oil concentrations and in the presence of suspended matter, the
peel oil distills off at a much reduced rate as in the following
case: a press liquor having 0.41 percent recoverable oil was
distilled; after 6.2 percent had distilled over, the recoverable
oil had decreased to 0.28 percent; after 9.2 percent distilled, it
was reduced to 0.20 percent; and after 21.7 percent, to 0.13
percent recoverable oil.
10 Florida Agricultural Experiment Stations
RATE OF CLARIFICATION
E 24.7 %
40 6.5 %
ED 1.2 %
( 0.0 %
50 70 90 110 130 150
TIME IN MINUTES
Fig. 2.-Influence of partial distillation and its consequent peel oil
removal upon clarification rate.
Citrus Molasses 11
Temperature and pH also have an important effect upon the
clarification of citrus press liquor. When press liquor is first
heated, a gradual increase in insolubles is noticeable as the
temperature rises. The suspended insolubles appear to agglom-
erate as the temperature approaches the boiling point of the
press liquor; then increased convectional turbulence redisperses
the flocs. A scale begins depositing on the inner heat transfer
surface of the vessel and increases with prolonged boiling. The
pH of the press liquor all the while is undergoing a slow decrease.
On the average the press liquor will decrease 0.2 of a unit by
the time it reaches its boiling point and will decrease approxi-
mately one unit when the press liquor has been converted to
citrus molasses. If more calcium hydroxide, such as used in
treating the citrus residue initially, is added to boiled-clarified
press liquor, considerable quantities of new flocculent-suspended
matter are precipitated. Although the quantity of suspended
matter in press liquor increased as lime was added, in the pH
range of 3.3 to 7.7 there was an improved settling rate of the
insolubles at the higher pH conditions.
The quantity of peel oil in press liquor is usually from 0.15
to 0.50 percent and is normally recovered by Florentine-type
chambers from the distillate of the flash chamber and multiple-
effect evaporators as an additional by-product. Press liquor
from oranges usually has a higher peel oil content than that
from grapefruit. The removal of peel oil by distillation was
accomplished more slowly from press liquors having higher pH
conditions, as shown in Fig. 3.
When citrus press liquor is clarified and subsequently con-
centrated to molasses, a much darker product is obtained. The
darker color of this improved product is sufficient to prejudice
some into believing the product has been burnt or overcooked,
whereas it appears dark only because there are fewer suspended
particles to reflect the incident light.
Although all heat transfer equipment is subject to the for-
mation of scale, few other industries meet with difficulties equal
those encountered in evaporating citrus press liquor to citrus
molasses. In Fig. 4 is shown a sample of citrus molasses evap-
orator scale. The thickness of the scale, 5 mm, is not unusual
and represents a serious heat transfer barrier. The dried scale
12 Florida Agricultural Experiment Stations
Cr RATE OF OIL REMOVAL
Recoverable Oil 0.36 %
10 pH 8.2
0 20 30 40
% PRESS LIQUOR DISTILLED
Fig. 3.-Influence of pH upon rate of peel oil removal from
press liquor by distillation.
press liquor by distillation.
Citrus Molasses 13
had a density of 0.75 and a 44 percent ash content on a dry
matter basis of which 61 percent was calculated to be calci-
um oxide. Spectrophoto-
graphic analysis showed.
magnesium, iron, silicon, 'l
and copper to be present
in more than trace quan-
tities. Quantitative esti-
mates by chromatogra-
phy and titration sub-
stantiated that at least
80 percent of the scale
was calcium citrate, the
remaining portion being
a less accurately deter-
mined mixture of pyro-
lyzed organic matter, cal-
cium phosphate, silica,
and other insoluble salts.
There was no hesperidin
in the scale, and if pec-
tates were present, the
quantity was less than 1
The industry has solved
in different ways the
vexing problem of seri-
ous scale formation on
heat exchange surfaces.
Most processors have
found it advantageous to
encourage scaling in the
press liquor preheaters,
which are more readily
cleaned than the main
tor. Simliarly, a parallel
arrangement of two iden-
tical preheaters allows a
more continuous process-
ing of c press liquor b Fig. 4--An enlarged cross-section of
ing of press liquor by citrus evaporator scale.
14 Florida Agricultural Experiment Stations
permitting the preheaters to be cleaned alternately without a
shutdown. Kilburn (17) suggested a more refined method
of decreasing the rate of scale build-up which involved sub-
stituting sodium hydroxide in part for lime in obtaining peel
liquor release. Waste lye from the lye peelers and other alka-
line solutions such as the molasses plant boil-out solutions have
been used with the additional advantage of decreasing the load
on the waste disposal system. The frequency of evaporator
boil-out was changed from every 48 hours to every two or three
weeks. The authors suggest that an improved rate of scale
formation might be obtained merely by using a less pure dehy-
drated lime, such as one having a higher quantity of magnesium.
Once the scale is formed, some method is needed to clean
the heat exchange tubes and evaporator surfaces. Dilute hydro-
chloric acid will dissolve all but 9 percent of the scale and has
been used to clean cane sugar evaporators; however, it may
be too corrosive even with corrosion inhibitors because of the
necessity for more frequent cleaning. A very effective method
of dissolving this scale is the use of a 5 percent solution of alka-
line ethylenediaminetetraacetic acid. Although expensive, it was
suggested as useful when conventional methods of cleaning an
evaporator fail (30). Citrus molasses evaporators are usually
cleaned of scale by a boiling alkaline solution of caustic or a
mixture of caustic and soda ash which is circulated over the
heat exchange surfaces. Under laboratory conditions a 10 per-
cent soda ash solution appeared to be as effective as a 3 to 7
percent caustic solution, and caustic by itself became increasingly
effective at higher concentrations. Tests with various phosphate
cleaning solutions failed to achieve the desired result, while
phosphate glasses that can sequester calcium were too expensive.
The use of these same compounds at economically lower dosage
rate was found to be ineffective, since the precipitation of cal-
cium citrate was delayed rather than prevented.
The froth fermentation or spontaneous foaming of molasses
has been the subject of much inquiry, and even though it hap-
pens infrequently, it can be a serious economic loss. This phe-
nomenon occurs when molasses spontaneously heats to such
high temperature as to boil and foam out of its storage tank,
leaving sometimes only a charred mass. More usually the molas-
Citrus Molasses 15
ses foams to some multiple volume that is greater than the
storage space available. All attempts to correlate this instabil-
ity with some other chemical or physical analysis have been
futile to date. Owen (28) corroborates this and has stated that
in blackstrap molasses the actual deterioration involving loss of
sugars was accompanied by gas evolution, but it was also true
that this cannot be taken as an indication of the destruction of
sugars. Hucker and Brooks (15) demonstrated that gas was
produced by mixtures of nitrogen compounds and glucose, a
reaction which has more commonly been known as the Maillard
In the laboratory the spontaneous foaming of citrus molas-
ses can be anticipated many times when the samples have shown
sub-surface gas formation during the first months of storage.
These samples foamed more readily when disturbed, much like
a carbonated beverage. It appeared significant that of 20 sam-
ples of clarified citrus molasses made in the laboratory, only
two showed any sign of sub-surface gas formation, and both
of these samples had an excessive precipitation of insolubles
during storage. None of these samples showed any sign of
surface foaming, but all had the advantage of a less stable
foam system. Among the conditions contributing to stable
foams are high viscosity and finely divided solids, both of which
were reduced by clarification. Shearon and Burdick (31), re-
ported that foaming in Texas citrus molasses was eliminated
when the insoluble solids were removed or reduced as much
as possible. Hucker and Brooks (15) demonstrated that high
viscosities increased the chances of spontaneous foaming and
that high storage temperatures further aggravated this con-
dition, with 40 to 450 C being a particularly critical temperature
range. The same authors proposed that microorganisms can
be considered only a minor cause in the production of foam.
In contradiction to the premise that microorganisms were
only a minor cause of molasses instability, citrus molasses pro-
ducers have successfully avoided this troublesome condition by
measures that suggested microorganism control. It has been
found advisable to avoid unduly prolonged storage of peel resi-
due, to inactivate microorganism and enzyme activity in press
liquor as quickly as possible, to hold press liquor in steel tanks
rather than wood, and to dispose of doubtful lots of press liquor.
After conversion to molasses, continuous recycling has been
used to avoid isolated pools of microorganism activity on the
16 Florida Agricultural Experiment Stations
surface edges where condensed water can dilute the product in
the larger storage tanks. Also it is possible that the infrequent
occurrence of foaming in recent years has coincided with unrec-
ognized processing changes. Clarification of press liquor has
been more prevalent both by settling in the storage tanks and
by the more judicious use of screens. Continuous recirculation
has reduced greatly the build-up in molasses viscosity.
All processors should be aware of and avoid the hazards of
high alkaline processing conditions, storing too warm a molasses,
and of mixing newly processed molasses with a molasses that
has been stored for any period of time.
Once the foaming or frothing has begun, there are a few
procedures that have been found helpful without any one being
a consistent remedy. Some form of agitation is always needed.
Compressed air has been tried, and although it is helpful by
both cooling and stirring the molasses, it has been replaced by
recirculation with the delivery pump. Under some conditions,
compressed sulfur dioxide has been added with success while
some blackstrap producers have injected live steam at four
atmospheres of pressure (37), and still others have covered the
surface with diesel fuel (29). If the foaming has begun and
the molasses is reprocessed through the evaporators a specific
anti-foaming agent is necessary in most all cases. Mechanical
foam breaking, according to Shkodin (32), is improved by coat-
ing the stirrer with paraffin wax, thereby getting improved wet-
ting action. Following is a summary of the corrective measures
to control foaming:
a. Compressed air
b. Recirculation pumps
2. Anti-Foam Agents
3. Temperature Control
a. Compressed air (cool)
b. Recirculation pumps (cool)
c. Live steam (heat)
Citrus Molasses 17
a. Recirculation or mixing
b. Sulfur dioxide
In storage, citrus molasses has been found to undergo slowly
physical and chemical transformations. Of paramount impor-
tance are the changes in sugar content which occur during
storage. It was shown in one study (13) that commercial citrus
molasses lost an average of 2 to 3 percent total sugars per year
of storage. In contrast, there was no loss in clarified laboratory-
prepared molasses. Owen (28), investigating the deterioration
of blackstrap molasses, found the samples having the highest
total sugar values to be the most susceptible to actual deteriora-
tion in storage. This did not seem to apply to the less concen-
trated citrus molasses samples.
During storage, as in processing, the pH of citrus molasses
continues to decrease. The decrease appears to be dependent
upon both the time of storage and the pH of the sample at
the time it was put in storage. The extent of this change in
pH versus storage time is shown in Fig. 5. Below a pH of
4.5, citrus molasses would appear to have a more stable pH.
The change in pH while in storage is not of great importance
in itself, but the more acid the molasses becomes the greater
the corrosive effect on the storage tanks. Consideration should
be given, therefore, to anticipating the decrease in pH that
will occur in processing press liquor and storing citrus molasses
and to the slightly increased need for lime in processing grape-
fruit peel compared to orange peel.
Many processors and customers have recognized that citrus
molasses in storage tends to increase in viscosity. This condi-
tion has at times been so serious as to cause solidification, al-
though many processors have never had this trouble. Since
high viscosity can lead to many difficulties in the handling and
utilization of this product, a study was made of this problem
(14). Representative citrus molasses samples were taken month-
ly from four processing plants and stored at 80 F after each
was adjusted to a degree Brix of 71 to 72. The initial viscosity
of each sample is shown in Table 6 and was determined at 800 F
with a Brookfield Synchrolectric viscometer. The data indicate
18 Florida Agricultural Experiment Stations
-0.6 0\ O
X Storage Time
-0.2 e\ 0
7 6.5 6 5.5 5
ORIGINAL pH OF MOLASSES
Fig. 5.-A scatter diagram presenting the pH change that occurred for
28 samples of citrus molasses while in storage.
Citrus Molasses 19
60 64 68 72 76 80 84
600 0 Temp. Vs. Viscosity at 75* Brix
400 Brix Vs. Viscosity at 300 C.
10 30 50 70
Fig. 6.-Influence of concentration and temperature upon the viscosity
of citrus molasses.
20 Florida Agricultural Experiment Stations
the variations in vicosity that normally occur between process-
ing plants and within a season. None of these samples exhibited
the low viscosity of 300 to 375 centipoises that is possible for a
fully clarified citrus molasses at this Brix. The influence of
temperature and concentration upon the viscosity of an excellent
sample of commercial citrus molasses is shown in Fig. 6. The
greatly increased viscosity brought about by low storage tem-
perature and high Brix levels is illustrated.
Total sugar content of the same molasses samples shown
in Table 7 was not correlated with the initial viscosity. Partial
fermentation and the related loss of sugars would require a
greater amount of concentrating to reach the same degree Brix.
Accordingly, the changed conversion ratio would have been ex-
pected to increase the percentage of insoluble solids which
contribute to high viscosities.
TABLE 7.-INITIAL VISCOSITY AT 800 F OF FRESHLY PRODUCED CITRUS
MOLASSES PROCESSED FROM FOUR PLANTS AND AT MONTHLY INTERVALS
THROUGHOUT THE 1950-51 SEASON.
Viscosity in Centipoises
Date Processed Plant A Plant B Plant C Plant D
11-18-50 4,140 8,500 1,960 1,200
12-21-50 2,000 16,000 2,840 1,550
1-19-51 2,000 4,800 2,000 2,500
2-20-51 2,300 1,500 1,900 750
4-12-51 4,200 11,600 2,500 3,100
5-17-51 47,500 8,000 1,800 1,700
6-27-51 19,500 10,600 2,900 2,300
The importance and serious attention that should be given
to viscosity are amply demonstrated in Fig. 7. Representative
molasses samples from each of four plants were placed in storage
at 80 F, and measurements were taken periodically over a 190-
day period. Deliberate sample stirring prior to measuring vis-
cosity was sufficient to obscure the increase in viscosity that
occurred during storage. It became obvious later that a gelatin-
ous structure was formed slowly in molasses during storage and
that it could be broken by stirring or heating. In most cases
the large increases in viscosity that occurred during prolonged
storage were eliminated almost entirely by vigorous agitation.
Further static storage, however, brought about new viscosity
increases at correspondingly similar rates. There were samples
Citrus Molasses 21
S30 Plant B 0
Plant C 9-- ,
n Plant D Samples
Pu l n- Stirred
Z testing /0
> 10 r
I Insolubles settling out ,
o I/-- -l- .....--- '
40 80 120 160
DAYS OF 800F. STORAGE
Fig. 7.-Rate of viscosity change of citrus molasses while in storage.
Fig. 8.-A microphotograph of naringin in citrus molasses
22 Florida Agricultural Experiment Stations
of sufficiently low initial viscosity that insoluble matter would
settle and thereby create a top, clearer portion of unchanging
viscosity as shown in Fig. 7. In still other samples, microscopic
examination of suspended insolubles showed a portion to be
clusters of crystalline needles, shown in Fig. 8. The crystalline
material was subsequently identified as naringin, and heating
of the molasses samples redissolved these crystals temporarily.
When rate of viscosity build-up during molasses storage was
calculated for each sample, a range of 60 to 2,000 centipoises
per day was found. The rates of viscosity increase were suffi-
ciently correlated to the initial viscosity that the initial value
was in itself the best guide toward anticipating future trouble.
A viscosity increase of more than 500 centipoises per day can
be expected to cause trouble, since the molasses without agitation
will increase its viscosity by 45,000 centipoises and probably
solidify within three months.
Quantity of pectin, pH, and total sugar content were not sig-
nificantly related to initial viscosity or to the rate of viscosity
increase while in storage, but insoluble solids and possibly small
differences in grade of pectin present were factors of greater
Citrus molasses finds its greatest market presently as a feed,
and as such was estimated by Becker, et al. (3) to contain 1.4
percent of digestible crude protein and 56.7 percent of total
digestible nutrients. They demonstrated that citrus molasses
when used at the 2 and 4 percent level effectively ensiled grass
and showed further that the bitterness imparted by naringin to
citrus molasses was not a detriment in feeding dairy cows.
Baker (1) at a later date estimated citrus molasses to have a
total digestible nutrient value of 53.3 percent and to have a
price value equivalent to 80 or 90 percent that of ground snapped
corn. In these trials, steers fed citrus molasses appeared to
have better appetites and were easier to keep on feed. Citrus
molasses replaced one-half of the ground snapped corn in the
steer fattening ration without reducing gains, finish, or yield
in this same feeding experiment. In later experiments, under
somewhat similar conditions, Baker (2) found that citrus molas-
ses could replace an equal weight of ground snapped corn with
Citrus Molasses 23
a consequent higher feed consumption, larger and cheaper gains,
earlier finish, and slightly higher dressing percentages. In
trials that investigated the feeding value of citrus products
for beef cattle, Kirk and Davis (18) found citrus molasses to
be palatable to all classes of beef cattle and to be one of the
cheapest energy feed available in central Florida. It was sug-
gested that molasses be combined with a high protein feed for
best results since it is essentially a carbohydrate concentrate.
At times the industry has supplemented the natural protein of
citrus molasses by adding 3 percent urea (60 pounds urea per
ton of molasses) to make a 12 percent protein equivalent prod-
uct that has been fed effectively under controlled conditions. A
further discussion of results with urea-fortified citrus molasses
in steer feeding trials has been described by Kirk et al. (20).
The controlled conditions required to effectively avoid urea
toxicity with this supplement were determined by Davis and
In a steer feeding trial by Chapman et al. (4) the compara-
tive feeding value of cirtus molasses, cane molasses, ground
snapped corn, and dried citrus pulp was evaluated for fattening
steers on pasture. Although average daily gains in this type
of feeding trial were neither large nor too different, citrus molas-
ses was shown to be more palatable than cane molasses. This
was somewhat of a disadvantage as it encouraged a too greedy
consumption at the expense of efficient utilization. Average
daily gains of better than 2 pounds per day were obtained in
all of a series of trials by Kirk et al. (19) in which pairs of
steers were fed a fattening ration of pangola hay, cottonseed
meal, citrus pulp, and either citrus molasses or blackstrap molas-
ses. The paired feeding trials showed both citrus and black-
strap molasses to be palatable and satisfactory in steer fattening
rations. Equal gains were obtained with the two types of
molasses when steers were hand-fed, but when self-fed, cattle
ate slightly more citrus molasses.
Cunha and co-workers (6) fed citrus molasses to swine and
found that it could be used to replace corn in the feeding ration
at the 10, 20, and 40 percent level, depending on age of the
pig. Citrus molasses was reported to have 91, 81, and 76 per-
cent of the respective feeding value of corn at the 10, 20, and
40 percent level in the ration. It took 3 to 7 days for the pigs
to become accustomed to the taste of citrus molasses in the
24 Florida Agricultural Experiment Stations
Other than as a feed for cattle, one of the major uses for
citrus molasses in recent years has been its fermentation to
ethyl alcohol, which in turn is sold as brandy neutral spirits.
The remaining distillery solubles, or still slop as it is sometimes
called, have been fed to range cattle; but other attempts to
utilize it in a concentrate form have not been successful.
Yeast production with Torulopsis utilis, a fast growing yeast,
was first evaluated in dilute citrus molasses by Nolte and co-
workers (27). Later, Veldhuis and Gordon (36) adapted the
fermentation into a continuous process. Yeast contains usually
about 50 percent protein and could be a valuable feed supple-
ment provided production costs were more favorable. Somewhat
similarly, lactic acid has been manufactured on pilot plant scale,
but its manufacture has since been discontinued.
A valuable use of citrus molasses has been in the recovery
of vitamin P, a name that has more recently been replaced by
the term citrus bioflavonoids. Sokoloff (33, 34) was granted pat-
ents on this application, but similar therapeutic factors have
been extracted from the peel itself by other methods.
Still other means of utilizing citrus molasses include the pro-
duction of bland syrup (12), citrus vinegar (24), 2,3-butylene
glycol (21), riboflavin and citric acid (10), methane (26), and
Processing techniques and analyses of citrus molasses were
studied and compared, as were intermediary, laboratory, and
related products. The one factor that would contribute most
toward making an improved molasses was found to be clari-
fication of citrus press liquor prior to concentrating. Obvious
advantages were a physically more attractive product, a lower
viscosity, a higher sugar content, a lower ash content, a higher
possible concentration, and improved storage stability.
Scale on heat exchange surfaces was established to be mostly
calcium citrate, and methods were described for both avoiding
its build-up and cleaning the heat exchange surfaces. Froth
fermentation or foaming of citrus molasses, which has only
rarely occurred in recent years, was investigated, and procedures
were described for decreasing the possibility of occurrence and
controlling the condition when it happened. Citrus molasses
Citrus Molasses 25
decreased slightly in sugar content and increased in viscosity
when stored for an extended period of time. The viscosity was
decreased greatly by agitation.
Review of uses for citrus molasses showed it to be palatable
to all classes of beef cattle. It has been used to replace ground
snapped corn in fattening rations with excellent results. Citrus
molasses was further shown to be useful in the recovery of
citrus bioflavonoids and manufacture of brandy neutral spirits,
feed yeast, lactic acid, bland syrup, citrus vinegar, methane,
2,3-butylene glycol, riboflavin, and citric acid.
Grateful acknowledgments are made to the commercial proc-
essors and manufacturers in the State of Florida whose coopera-
tion contributed to the success of this work. Citrus molasses
samples used in part of this study were obtained from Florida
Fruit Canners, Inc., Frostproof; Peace River Canning Company,
Wauchula; Florida Molasses Corporation, Lake Alfred; Florida
Citrus Canners Cooperative, Lake Wales; Kuder Citrus Feed
Company, Lake Alfred; Pasco Packing Company, Dade City;
Plymouth Citrus Growers Association, Plymouth; Suni Citrus
Products Company, Haines City; Southern Fruit Distributors,
Orlando; Winter Garden Citrus Products Cooperative, Winter
Garden; Adams Packing Association, Inc., Auburndale; and J.
William Horsey Corporation, Plant City. For all their courtesies
and contributions the authors express their appreciation and
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Citrus Molasses 27
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