Summary of citrus processing and by-products research projects.
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Title: Summary of citrus processing and by-products research projects.
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Creation Date: 1958
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Year Ending June 30, 1958

Florida Citrus Experiment Station and Florida Citrus Commission
Lake Alfred, Florida


State Project 550 R. Patrick and E. C. Hill

Identification of Microorranisms in Citrus Concentrates. Three hundred
and forty samples of orange and grapefruit juice or concentrate were collected
for observations and analyses. These included 212 commercial samples of fro-
zen orange concentrate and 99 commercial samples of frozen grapefruit concen-
trate obtained during the 1956-57 season, and 29 orange juice or concentrate
samples obtained from freeze-damaged fruit. About 72 percent (244) of the
samples examined contained streptococcus-like microorganisms; 11 percent (26)
of these cultures survived the presumptive test for enterococci and about 5.5
percent (13) survived the confirmatory test. Seven of these cultures were
similar to Streptococcus liauefaciens, although they failed to survive 62oC.
for 30 minutes, failed to coagulate or produce acid in milk containing 0.1
percent methylene blue, and did not impart a bitter taste to the proteolyzed
casein. The 6 remaining cultures failed to grow at pH 9.6 at 370C. and also
failed to coagulate milk in the presence of 0.1 percent methylene blue; other-
wise the cultures were similar to S. faecalis; four of these cultures were
isolated from juice of cold-damaged fruit extracted in the Station pilot plant.
Streptococcus-like organisms were destroyed readily in juice by heating to
1650F. in a plate type heat exchanger, the juice remaining in the heating
section of the exchanger for 14 seconds.

Microorganisms that produced gas in lactose broth were found in 17.3 per-
cent (59) of the 340 samples analyzed. When cultures of these organisms were
streaked on E.M.B. agar, only three of them resembled coli-like colonies and 15
resembled Aerobacter aerogenes.

Results obtained from the examination of these samples confirmed previous
observations that juice from either cold-damaged, overmature, or mishandled
fruit often contains coli-like or streptococcus-like organisms; such organisms
are usually killed when exposed to temperatures ranging from 1650 to 1750F. The
occurrence of coliform organisms and streptococci in commercial frozen citrus
concentrates may result from either the use of unheated cutback juice or recon-
tamination of juice in the cooling section of a regenerative heat exchanger. It
was also evident that the microbial status fouid in the commercial samples of
frozen concentrated orange and grapefruit juices was very different from that
which exists in citrus juices immediately after extraction because of heat
treatment of the juice either prior to or during the concentration process.

Examination of Lemon Juice and Concentrate for Lemonade. Forty-two raw
lemon juices and 42 samples of concentrate for lemonade, prepared from each of
these lemon juices by the addition of sugar and the same folded lemon oil, were
examined during October, November, and December for microbiological content by
plating on dextrose, potato dextrose, and orange serum agars. Also, a 1:10
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred. Florida. 86Q in/l/lt uPr


dilution of each sample of juice or concentrate was inoculated into lauryl
tryptose broth for the detection of coliform bacteria and also streptococci.

The microbiological content of the lemon juices ranged from 100 to 22,000
per milliliter on dextrose agar; 100 to 22,000 on potato dextrose agar; and 100
to 23,000 on orange serum agar. The concentrates for lemonade, examined immedi-
ately after preparation and prior to freezing, showed counts ranging much lower;
100 to 5,900 per milliliter on dextrose agar; 100 to 5,500 on potato dextrose
agar; and 100 to 5,700 on orange serum agar. Relatively high counts of 80,000,
100,000, and 60,000 per milliliter on dextrose, potato dextrose, and orange
serum agars, respectively, were found when one sample of raw lemon juice ex-
tracted from freeze-damaged and overmature fruit was examined in January.

No coliform bacteria or streptococci were found in any of the lemon juice
or concentrate samples. Gas was produced when 31 of the concentrates for lemon-
ade were inoculated into lauryl tryptose broth; yeast grew and was thought to be
the cause of fermentation; however, yeast also grew in nine other inoculated
tubes but no gas was produced.

Examination of Freeze-Damaged Oranges. Juices extracted from lots of
Hamlin, Parson Brown, Pineapple, and Valencia oranges, which were damaged by
cold temperatures, were subjected to microbiological inspection. The fruit was
extracted and finished so that variations in juice yield and pulp content were
obtained. Dextrose, potato dextrose, and orange serum agars were used as
plating media.

The plate counts for juices from Hamlin or Parson Brown oranges increased
with an increase in pulp content or yield of juice varying from 31,000-37,000
per milliliter for low yields to 924,000-3,100,000 per milliliter when high
yields of juice were obtained. When fruit was held at room temperature for 24
hours, the counts increased from 31,000-37,000 to 122,000-140,000 per milliliter;
also, after 3 days storage at 400F. to 670,000-800,000 per milliliter. Strepto-
cocci were present in the juices, but failed to grow in the Difco enterococcus
screening medium. Yeast and leuconostoc became predominating contaminants in
Hamlin oranges stored at 400F. for 10 to 15 days. A similar condition was
observed in Parson Brown oranges after 5 days storage. The lactose-fermenting
bacteria found were atypical coliforms.

The plate counts for the juice from freeze-damaged Pineapple oranges were
high initially but decreased to 4,000-10,000 per milliliter after 15 days at
400F. Pineapple oranges not damaged by freezing, taken from Station plots,
showed moderate contamination initially and three days later after storing at
400F., the count ranged from 900-3,000 per milliliter. Coliforms present formed
atypical growths on E.M.B. agar. Streptococci were found in abundance, but
failed to grow in Difco enterococcus screening medium.

Freeze-damaged Valencia oranges extracted and finished to give high yields
of juice and high pulp contents showed plate counts of 21,000-51,000 per milli-
liter as compared to 7,000-11,000 per milliliter when set for low juice yields
and low pulp contents. Coli-like colonies were found in juices during the

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 a 10/2/58 FWW


earlier part of the season, but in later tests coliforms were atypical. A
different lot of fruit was tested in which counts were higher initially but re-
mained about the same over a period of 15 days at 400F. The initial juices in
this lot contained Aerobacter, but thereafter the coliform colonies were atypi-
cal. Streptococci were present in all of these Valencia juice samples, but the
organisms failed to grow in Difco enterococcus screening medium.


State Project 607 J. W. Kesterson and R. Hendrickson

The principal purpose of this investigation is to determine by what means
essential oils of very high quality can be produced in Florida. Under study
are such factors as methods of extraction, stability, methods of processing,
flavor, fruit variety, and fruit maturity.

The quality of citrus oils produced by the screw press and FMC In-Line
extractor were evaluated during the 1957-58 season. The physical and chemical
properties of all samples were considered normal. There was no adverse effect
on oil quality due to the December freeze.

A preliminary survey was made to evaluate the quality of lemon oil pro-
duced from 42 lemon varieties and selections grown in Florida. Samples of oil
were prepared in the pilot plant and the physical and chemical properties of
these oils were determined. The oils produced from 18 of these lemons failed
to meet the minimum requirements of the United States Pharmacopoeia. From the
standpoint of aldehyde content and yield of oil, the 10 best lemons which met
the minimum standards of the U.S.P. are as follows: Aldehyde Content Sicilian,
Bearss #1, "M" Lemon, Bearss #2, Italian, Citrus Experiment Station Block III
G-5, Villafranca, Des-4 Saison, Harvey #2, Sexton #2, and Harvey #1; Yield of
Oil Sicilian, Bearss #1, Bearss #2, Des-4-Saison, Sexton #2, Corregia, "4M"
Lemon, Villafranca, Italian, and Moreland.

A preliminary investigation indicates that it may be possible to use
ultraviolet and infrared techniques to detect oxidation of essential oils.


State Project 611 E. L. Moore, A. H. Rouse, and C. D. Atkins

Packs of 420 Brix Pineapple and Valencia orange concentrates, prepared as
previously described (1957 Ann. Rpt., p. 199) were stored at -8o, 100, 200,
300, and 400F. to investigate further the relative effect of heating either
the single-strength juice prior to evaporation or 2-, 3-, and 4-fold concen-
trates withdrawn during the evaporation of unheated juice and subsequently
heat treated.

The physical stability of these 1957 Pineapple orange concentrates followed
the trend of similarly prepared 1954 Pineapple and Valencia orange concentrates

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 b 10/2/58 FWW


as previously reported (1956 Ann. Rept., p. 175). The best and poorest pro-
tection against clarification in concentrates during storage was found in those
prepared from juices heated at single-strength and 4-fold, respectively. Con-
trary to the findings for the above three series of packs, the 1957 Valencia
orange concentrates showed the best and poorest protection against clarifica-
tion during storage in those prepared from juices heated at 3-fold and single-
strength, respectively. For these 1957 Valencia orange concentrates, the ex-
tracted juice before finishing was passed through a pump that cut the pulp
particles to uniform size and liberated more water-soluble pectin. Thus, it
appeared that other processing procedures could have as great an influence on
the physical stability of Valencia orange concentrate as the procedure used
for heat treatment.

Additional packs of 420 Brix Valencia orange concentrates were prepared
from both uncut and cut juices. In the preparation of these 1958 concentrates,
the single-strength juice was heated to 165oF. prior to evaporation or 2-, 3-,
and 4-fold concentrates were withdrawn during the evaporation of unheated juice
and subsequently heat treated at this temperature. The heated juice and con-
centrates were then individually concentrated to 550 Brix, and cut back to 420
Brix with uncut and cut 0.020-inch finisher juice, respectively.

These 1958 Valencia orange concentrates are being stored at -8, 10o, 20o,
and 40OF., and are being examined at periodic intervals. In general, based
on analyses to date, retention of cloud at the higher storage temperatures is
better in the concentrates prepared from juices heated at the higher folds.
This is being found for concentrates prepared from both uncut and cut juices.
Thus, it appears that there are possibly processing, fruit, and other unknown
factors which in part determine the most advantageous stage at which to apply
heat treatment in the concentration process.

State Project 622 J. W. Kesterson and R. Hendrickson

The principal purpose of this investigation is to determine the quantity
of naringin in grapefruit as related to fruit size, season, maturity, and dry
solids content of whole fruit; as well as to determine practical methods for
the recovery of this chemical from whole fruit and waste peel.

The proper processing procedure for the recovery of this bioflavanoid
had previously been worked out in the laboratory, and this information was
used as a basis for operating the pilot plant. Six pilot plant runs were
made and 75 pounds of purified naringin produced. In pilot plant work it was
found that the wet naringin filter cake must be dried immediately in order to
obtain a product of high purity. If not dried immediately it will mold and
the purity of the finished product will be considerably reduced.

Fermentation of the press liquor was found to considerably reduce the
recovery of naringin. To combat this problem sodium bisulfite was added in a
concentration of 600 ppm and gave most satisfactory results. The addition of
this quantity of sodium bisulfite reduced the filtration time for a 1780-gallon
batch from 8 to 4 hours. This was evidently accomplished by the fact that the
sodium bisulfite destroyed the slime organisms which normally grow in press
Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 10/2/58 FWW 869 c

A new ultraviolet method for determining the naringin content of grapefruit
juices was investigated and showed excellent promise. The method depends on the
peak absorption of naringin at 284 mu at which wavelength naringin has a molar
absorptivity of 19,000. Besides establishing most of the important conditions
for consistent results with this method, it was found that the ultraviolet
absorption spectrum appeared capable of measuring quantity of peel extractives
and the degree of abusive processing conditions. The procedure was also felt
to have substantiated that naringin analyses of late season grapefruit juice
by Davis test do not read discriminatingly high as some believe.


State Project 646 R. Hendrickson and J. W. Kesterson

The main objective of this investigation is to determine the hesperidin
content of the important varieties of citrus; to study its commercial recovery
from both waste peel and whole fruit; and to investigate the profitable utili-
zation of hesperidin.

The pilot-plant production of purified hesperidin and hesperidin complex
was studied for an additional season. The recovery of purified hesperidin was
increased 35.5 percent, and recovery of hesperidin complex was increased 12.5
percent. This increased yield is attributed to utilization of sodium bisulfite
and an improved drying procedure.

In a continued evaluation of eight analytical techniques of assaying
bioflavanoids, three methods were found to have only limited application.
Chromatography was found to be the most specific method though somewhat limited
by being semi-quantitative. Of the four most satisfactory photometric proce-
dures, the azo coupling method was the most sensitive, the ultraviolet analysis
the most specific, the Arcangeli-Trucco determination the most tedious, and the
Davis test was thought to be most suited for routine assaying while the azo
coupling method and ultraviolet had more advantage when and if mixtures of
citrus bioflavanoids needed to be assayed.

As part of an over-all attempt to select the lemon variety most suited to
Florida conditions from 42 lemon varieties and selections, the bioflavanoid
content of a representative quantity of peel from each of these lemons was ex-
tracted for hesperidin. The ten lemons having the highest hesperidin content
were: Villafranca, Sexton #2, Kusner, Corregia, Lemon Species 2/10/12,
Hogsette, Des-4-Saison, Italian, Eureka, and Lisbon. Chromiatographic analysis
has shown few differences to date, while ultraviolet examination of peel ex-
tracts is still incomplete.


State Project 649 C. D. Atkins, A. H. Rouse and E. L. Moore

Examination of Commercial Frozen Orange Concentrates. Determinations were
made of some of the physical and chemical qualities of 212 samples of commercial

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 d 10/2/58 FW


frozen concentrated orange juices obtained during the 1956-57 season from 24
plants in Florida during the months of December 1956 through June 1957. Degree
of gelation was determined on the concentrates, and reconstituted juices were
used for the other analyses. Pectinesterase activity immediately after thawing,
expressed on a soluble solids basis and multiplied by 1,000 for easy interpre-
tation, ranged from a low of 1.3 to a high of 15.8 units, with 89.6 percent of
the samples containing less than 10 units. Water-soluble pectin, expressed as
anhydrogalacturonic acid, varied from 30.7 to 65.3 milligrams per 100 grams of
juice; 90.6 percent contained from 30 to 49 milligrams per 100 grams. Water-
insoluble solids, indicative of extracting and finishing operations, were found
in 94.8 percent of the juices to range between 100 milligrams and 224 milligrams
per 100 grams; the lowest amount of water-insoluble solids found was 102 milli-
grams while the highest was 284 milligrams per 100 grams of juice. Alcohol-
insoluble solids ranged from 340 to 613 milligrams with an average of 446 milli-
grams per 100 grams of juice. Pulp content, by volume, in the juices showed a
variation of 8.0 to 18.0 percent.

Examination of the concentrates immediately after thawing indicated that
gel lumps were absent in 94.3 percent, the occurrence of gelation was questionable
in 5.2 percent, and slight elation was evident in only 0.5 percent. The samples
did not show any clarification when initially examined. After the storage or
"abuse" test of 96 hours at 400F., gelation and clarification were again deter-
mined. Fifty-seven percent of the concentrates were free of gel lumps and 43
percent showed very slight to slight gelation. Clarification was slight in
13.7 percent, definite in 9.9 percent and extreme in 1.9 percent of the samples,
with 74.5 percent showing no appreciable loss of cloud.

Examination of Commercial Frozen Grapefruit Concentrates. Ninety-six
samples of commercial froLen concentrated grapefruit juice, obtained during the
1956-57 season, were examined for some characteristics that determine their
physical and chemical stability. Pectinesterase activity in these samples was
restricted to a narrow range of 0.4 to 3.8 units with 75 percent of the samples
being within the range of 0.4 to 1.9 units. These pectlnesterase values indi-
cated that effective heat treatment was used in preparation of these grapefruit
concentrates. The pulp content, determined by volume, was distributed over the
range of 4.6 to 15.0 percent with an average of 8.4 percent. The pectic con-
tent of the samples determined on the centrifuged portion of the juice varied
from 20 to 39 milligrams per 100 grams in 69.8 percent of the samples. Water-
insoluble solids in the reconstituted juices ranged from 50 to 99 milligrams
per 100 grams in 87.5 percent of the products, the lowest value being 38.8
and the highest value 134.8.

None of these samples showed any initial clarification or gelation. After
storage at 400F. for 96 hours, slight gelatin was noted in eight concentrates.
Under the same conditions of storage slight clarification occurred in two
products and definite clarification in one sample.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 e 10/2/58 FWW


State Project 817

W. F. Newhall

The purpose of this project is to synthesize from citrus terpenes, particu-
larly d-limonene, chemical compounds which will extend the uses of these
materials and bring a better monetary return to the citrus industry.

During the past year work has been directed toward the synthesis of glycol
esters from d-limonene. Such compounds are of possible use to the chemical
industry as plasticizers and lubricating oil additives.

By partial hydrogenation followed by performic acid oxidation, d-limonene
has been converted in 60% yield to a crystalline mixture of isomeric glycols.
This mixture has been converted in 94% yield to the hitherto unreported diacetate,
dipropionate and dibutyrate esters by refluxing with the appropriate acid
anhydride. In this way saturated glycol esters were prepared from d-limonene in
50-55% yield. These esters are extremely stable high boiling liquids.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 f 10/2/58 WFN


Pectin and Pectic Enzymic Studies of Citrus Fruits and Citrus Processed
Products. To study the effect of arsenic sprays on the quality of canned
grapefruit sections, Silver Cluster grapefruit picked from both arsenated and
unarsenated trees were processed in December 1956 and January, February, and
March 1957. These canned grapefruit sections were then stored for 36 weeks at
800F. and examined periodically for physical changes in appearance and for
chemical changes in water-insoluble solids and pectic fractions. There was no
darkening of the sections during storage. Sections canned from grapefruit
picked in March showed signs of softening after only 12 weeks of storage but
all other packs remained firm. Water-insoluble solids were approximately the
same in the sections regardless of arsenation and picking date of the fruit, and
remained constant during storage. Water-soluble pectin was always greater in
the sections of unarsenated grapefruit than in sections from arsenated grapefruit
and there was no change in this fraction during storage. The ammonium oxalate-
soluble pectin usually increased during storage, while in general, the sodium
hydroxide-soluble pectin (protopectin) decreased about 50 percent during storage.
As an exception, the sections of arsenated grapefruit picked and processed in
March 1957 remained the same in protopectin during their storage life. (A. H.
Rouse, C. D. Atkins, and E. L. Moore.)

Data were obtained for the second year of a three-year study to determine
the effect of borax and arsenic sprays on some characteristics of juice extracted
from Marsh grapefruit. Amounts of spray application and results for the first
year were previously reported (1957 Ann. Rept., p. 238). Data on juices from
grapefruit which received no boron spray, but received different levels of
arsenic sprays, were similar to those in which the trees received boron spray,
except for water-insoluble solids and pectinesterase activity. Average values
of eight samples showed that boron sprayed trees produced fruit with 105.3
milligrams of water-insoluble solids per 100 grams compared with 96.9 milligrams
per 100 grams in juice from trees not sprayed with boron. Pectinesterase activ-
ity of juice from boron sprayed trees was 11.1 units compared with 12.8 units
for non-sprayed trees. Water-insoluble solids were found to be approximately
doubled during the second year of study, whereas the pectinesterase activity was
similar for the past two seasons. (A. H. Rouse, C. D. Atkins, E. L. Moore, and
E. J. Deszyck.)

Preliminary investigations were made of pectinesterase activity and pectic
content in healthy and diseased citrus roots for identification purposes.
Shredded woody roots from healthy trees and burrowing nematode infested trees
were soaked in a 1.0 percent sodium chloride solution for two hours for maximum
enzymic extraction and optimum reaction was found to be at a pH of 8.5. Pectin-
esterase activity was found to range lower in healthy roots (3.1 to 8.4 units
per gram) than in diseased roots (5.1 to 13.2 units). Activity increased with
root growth as the growing season advanced. Little difference was found in the
pectic fractions between healthy and diseased roots. Total pectin ranged from
62 to 86 milligrams per 100 grams of roots. Dry solids by vacuum were always
higher in the diseased roots. Further research will continue to determine if
the preliminary data are significant. (A. H. Rouse, C. D. Atkins, and R. W.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 g 10/2/58 FWW


A comparison was made of some constituents of juices extracted from sound
and frozen Pineapple and Valencia oranges and seedy grapefruit. Fruit was cut
and separated on the basis of internal appearance into three classifications
(State of Florida Citrus Laws 1957), namely, not damaged, damaged, and
seriously damaged. Harvesting dates for fruit used were as follows: Pineapple
oranges, January 16, which were subjected to the December 1957 and January 1958
freezes; seedy grapefruit, February 25, and Valencia oranges, April 17, April 21,
and May 23, 1958, all of which were subjected to the cold temperatures in the
vicinity of the Citrus Station. The only common differences found between the
juices extracted from sound and freeze-damaged fruit were lower acidities that
resulted in increased Brix-to-acid ratios, and an increase in both pH and
flavonoids in the fruit more seriously damaged.

Juices from Pineapple oranges and seedy grapefruit which were frozen when
they were mature were similar in many characteristics, whereas juices extracted
from Valencia oranges, which were immature during the freezes, did not have all
of these same characteristics and therefore may have healed themselves chemically
as they matured. Juices from damaged Pineapple oranges and seedy grapefruit in-
creased in serum pectin, viscosity, cloud, and water-soluble pectin, whereas
pectinesterase activity and sodium hydroxide-soluble pectin (protopectin) de-
creased; oxalate-soluble pectin increased very slightly. However, in juices
from freeze-damaged Valencia oranges, soluble solids, pectin serum, viscosity,
and water-soluble pectin decreased and sodium hydroxide-soluble pectin increased
or remained about the same compared with the same characteristics for sound
Valencia oranges. This was opposite to that found in juices from freeze-damaged
Pineapple oranges and seedy grapefruit. The cloud and ammonium oxalate-soluble
pectin was the same in juices from both sound and damaged Valencia oranges;
pectinesterase activity, which is associated with solid particles, varied in
most instances with the water-insoluble solids but not in relation to the degree
of freeze damage. (A. H. Rouse, C. D. Atkins, and E. L. Moore.)

Flavor of Processed Citrus Products. The flavor of 96 commercial samples
of frozen concentrated grapefruit juices, collected during the 1956-57 season
from 15 plants, was evaluated by a taste panel. The flavor of all of these
samples was of acceptable quality, except one which was graded "poor" because of
an off-flavor; 66 of the concentrates were graded "good" and 29 samples were
graded "fair".

Study continued on the important problem of determining those processing
factors that adversely affect the flavor of frozen concentrated orange juice.
Accumulating results indicate the importance of carefully controlling yield of
juice, pulp content, recoverable oil content, and stabilization temperatures if
concentrates of good flavor are to be produced. (F. W. Wenzel and R. W. Olsen.)

Standardization of Processed Citrus Products. Characteristics were deter-
mined on 212 commercial samples of frozen concentrated orange juice and 96
commercial samples of frozen concentrated grapefruit juice that were processed
during the 1956-57 season; these samples were collected from 24 plants with the
assistance of personnel of the Agricultural Marketing Service, USDA, Winter
Haven, Fla. Measurement of the color differences in these products was made
with the Hunter Color Difference Meter.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 h 10/2/58 FWW


Soluble solids in the frozen orange concentrates ranged from 41.0 to 43.50
Brix; total acid, as citric, 246 to 3.60 percent; Brix-to-acid ratio, 11.7 to
16.9; and ascorbic acid, 112 to 212 milligrams per 100 grams, which corresponded
to 33 to 63 milligrams per 100 milliliters in the reconstituted juices. Re-
coverable oil varied from 0.015 to 0.068 milliliter per 100 grams of concentrate,
corresponding to 0.004 to 0.020 percent by volume in the reconstituted juices.
Hunter "a" values ranged in the orange concentrates from 2.3 to 11.4; "b" values,
28.2 to 34.6; and "Rd" values, 18.2 to 32.0. Total glycosides, expressed as
hesperidin, varied from 53.5 to 118.6 milligrams per 100 milliliters in the
reconstituted juices. Diacetyl values obtained were from 0.0 to 2.2 parts per
million; the diacetyl value is the diacetyl equivalent of diacetyl and/or
acetyl-methylcarbinol in 25 milliliters of distillate from 300 milliliters of
reconstituted juice.

Soluble solids in the frozen grapefruit concentrates varied from 37.90 to
47.50 Brix; total acid, as citric, 3.60 to 4.69 percent; Brix-to-acid ratio,
8.7 to 11.5; and ascorbic acid, 94 to 163 milligrams per 100 grams, equivalent
to 28 to 48 milligrams per 100 milliliters in the reconstituted juices. Re-
coverable oil ranged from 0.002 to 0.125 milliliter per 100 grams, corresponding
to a trace to 0.037 percent by volume in the reconstituted juices. Hunter "a"
values varied from -6.3 to -2.4; "b" values, 16.2 to 24.8; and "Rd" values, 13.8
to 29.9. Total glycosides, expressed as naringin, ranged from 32 to 75 milli-
grams per 100 milliliters in the reconstituted grapefruit juices; naringin varied
from 19 to 46 milligrams per 100 milliliters, as determined by the difference in
total glycosides before and after hydrolysis of the naringin by a glycosidase.
Diacetyl values found were from 0.0 to 1.7 parts per million. (R. L. Huggart,
R. W. Barron, and E. C. Hill.)

After examination of sweetened canned grapefruit juices packed during the
1956-57 season (1957 Ann. Rept., p. 234), the Agricultural Marketing Service,
USDA, Washington, D. C., reported that they found no taste differences between
grapefruit juice sweetened with sugar and that sweetened with the artificial
sweetener, Sucaryl. As a result, 2600 cases of grapefruit juice sweetened with
Sucaryl were processed and canned at Snively Groves, Inc., Winter Haven, Fla.,
and these will be sent for market testing to several super-markets in a medium
size city. (R. W. Olsen and R. W. Barron.)

Frozen concentrates for lemonade were made from juices extracted from 42
different selections of lemons to determine if such fruit was suitable for this
purpose. The fruit was harvested and processed from October 14 through
December 20; 40 of the lots of fruit were supplied by Minute Maid Corporation,
Orlando, Fla., and two of the lots by Libby, McNeill and Libby, Ocala, Fla.
Total acid, as citric, in the lemon juices varied from 5.16 to 6.41 grams per
100 milliliters; yield of juice from the fruit, 3.76 to 5.80 gallons per 90
pounds; yield of acid, 1.69 to 2.76 pounds per 90 pounds of fruit. Frozen con-
centrates for lemonade were made from each of the 42 lemon juices. Sugar was
added to the juice so that a Brix-to-acid ratio of 15 to 16 was obtained and then
coldpressed lemon oil, prepared from the same fruit from which the juice was
extracted, was added. The products were canned, frozen, and stored at -80F.
until used. All of the concentrates, except two, were found to be acceptable
and to have a satisfactory lemon flavor; the product made from Meyer lemons did

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 i 10/2/58 FWW

not have a good typical lemon flavor and another sample of concentrate was
excessively bitter and astringent because of the use of excessive pressure dur-
ing extraction and finishing of the juice used. (R. W. Olsen, R. W. Barron,
R. L. Huggart, and F. W. Wenzel.)

Characteristics of Processed Citrus Products Made from Freeze-Damaged Fruit.-
Because of the severe damage to the citrus crop caused by the extremely cold
temperatures that occurred during the 1957-58 season, major emphasis was placed
upon investigations of various problems concerning the use of freeze-damaged
fruit in frozen concentrated orange juice. Many experimental packs were pro-
cessed in the pilot plant and the collection and examination of commercial
samples throughout the season was very extensive. Data are being accumulated
from the examination of these products and final evaluation of all information
obtained will not be possible until storage studies are completed during the
next year. Experimental packs of frozen orange concentrate were processed to
obtain as much information as possible on the following major problems (a)
effect of the use of freeze-damaged fruit on the chemical, physical, and organo-
leptic properties of this product, both initially and after storage, (b) develop-
ment of procedures for determining the extent of freeze damage in oranges, other
than by cutting followed by visual examination of internal appearance of the
frozen fruit, (c) determination of maximum amounts of cold-damaged fruit that
can be used with undamaged oranges to produce concentrate of acceptable quality,
and (d) changes in processing procedures necessary for the production of
acceptable frozen orange concentrate when using damaged fruit.

Previously during the 1956-57 season, experimental samples of frozen orange
concentrate were processed from Hamlin, Parson Brown, Pineapple, and Valencia
oranges that had been damaged by cold temperatures that occurred in the northern
area of the citrus belt in November, 1956. Results obtained from the examination
of these products during the past year and prior to the freeze of December,19'7,
confirmed previously reported information (1957 Ann. Rept., p. 235) concerning
the effect of the use of freeze-damaged fruit on the characteristics of frozen
concentrated orange juice, the most important being that problems relating to
physical stability and flavor were magnified when damaged fruit was used. How-
ever, results also showed that if the usual processing procedures were modified,
then frozen orange concentrate of good stability and acceptable flavor could be
produced from freeze-damaged fruit; the use of less pressure during extraction
and finishing of the juice, a stabilization temperature of 1950F., and control
of the peel oil and pulp content in the concentrate were found to be advantage-
ous. These conclusions have been further confirmed by data so far obtained from
the examination of samples of both experimental and commercial packs processed
following the major freeze of December, 1957.

Two hundred commercial samples of frozen concentrated orange juice, all of
which, except one, were packed from December 31, 1957, to January 8, 1958, in-
clusively, were collected from 18 processing plants so that concentrates con-
taining juice from some freeze-damaged fruit could be evaluated as to their
physical stability and flavor. Initially, all of the samples showed no separation
or clarification and no gelation of any practical importance. After storage at
800F. for 24 hours, 89.5 percent of the samples showed no significant loss in
cloud, while slight, definite, and extreme degrees of clarification were found

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 j 10/2/58 FWW


in 3.5, 4.0, and 3.0 percent, respectively; a slight degree of gelatin was
evident in 10.5 percent of the samples and a semi-gel occurred in 0.5 percent
or only one sample. Pectinesterase activity in the concentrates varied from
0.3 to 5.5 units and the pulp content ranged from 8.5 to 17.0 percent, by volume,
in the reconstituted juices. Flavorwise, most of the products were acceptable,
but of only fair quality.

A total of 59 samples of frozen concentrated orange juice for manufacturing
(bulk concentrate) were obtained from 22 commercial plants; 28 samples were pro-
cessed from December 28, 1957, to January 10, 1958, 18 samples from January 20
to February 7, and 13 samples from March 14 to April 14. The flavor of all of
these samples, except two, was acceptable, but of only fair quality, when they
were examined initially; oxidized and buttermilk type off-flavors were detectable
in the two unacceptable samples. The initial flavor of 35 of the 46 bulk concen-
trates, packed when early and midseason fruit was available, was maintained
during storage of the products at -80F. for approximately three months; slight
flavor deterioration occurred in 6 of the samples, and 5 of the products became
unacceptable because of the development of objectionable off flavors. The
physical stability of the 59 samples was found to be satisfactory, although
slight gelation occurred in some of the concentrates after storage for 24 hours
at 800F.; definite clarification was found in only one sample. Soluble solids
in the bulk concentrates ranged from 42.0 to 66.70 Brix; total acid, as citric,
2.93 to 6.31 percent; Brix-to-acid ratio, 10.0 to 19.5; and pH, 3.4 to 3.7. The
pulp content in the reconstituted juices of approximately 120 Brix varied from
7 to 18 percent, by volume, and the Hunter Color Difference Meter "Rd" values
ranged from 19.0 to 26.5, "a" values from -7.1 to -2.8, and "b" values from
25.2 to 30.3.

Samples of commercial frozen orange concentrate were collected semi-monthly
from Florida plants throughout the 1957-58 season. These 193 samples are being
examined for various characteristics so that a comparison may be made with re-
sults obtained from similar surveys during seasons when there were no major
freezes in Florida. Results obtained from the initial examination of these
samples for flavor, color, and stability indicate that the flavor of almost all
of these concentrates was acceptable; however, in general, both the flavor and
the color were not as good as that found in commercial frozen orange concentrates
packed during the 1956-57 season. The physical stability of these products was
good and better than that in concentrates obtained during the previous season.
(F. W. Wenzel, A. H. Rouse, R. W. Olsen, E. L. Moore, M. D. Maraulja, R. L.
Huggart, G. H. Ezell, R. W. Barron, and C. D. Atkins.)

Viscosity of Concentrated Citrus Juices. Various instruments and proce-
dures were investigated for measuring the viscosity of concentrated citrus
juices. These products are non-Newtonian liquids having thixotropic properties.
Any method must specify the instrument and accessories used, the rate of shear,
the treatment of the sample prior to the measurement, and the temperature of the
sample at the time of measurement. The Brookfield viscometer was found to be
the most suitable, after using it along with the Stormer viscometer, a stainless
steel orifice-type viscometer (Mitche3l), and a standardized pipette. Most of
the viscosity determinations on commercial and experimental samples of citrus
concentrates were made using the Brookfield instrument with the No. 2 spindle at
12 r.p.m. and with the measurement being made after one minute of operation.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 k 10/2/58 FWW


The samples were maintained at 3000. in a 6-oz. concentrate can.

The viscosity of 100 commercial samples of frozen concentrated orange juice
produced during the 1956-57 season ranged from a low of 430 centipoises to a
high of 2500 centipoises; concentrates produced while midseason fruit was avail-
able were, in general, more viscous than those packed during the late season
period. Results obtained from the examination of both commercial and experi-
mental products also indicated that the degree of concentration and the pulp
content of the citrus concentrates are very important factors influencing
viscosity and that some relationship may exist between the viscosity and the
physical stability of such products. (George H. Ezell.)

Recovery of Fruit Solids from Orange Pulp. An investigation was begun of
the recovery by water extraction of soluble solids from orange pulp that is ob-
tained during the extraction and finishing of orange juice in citrus processing
plants. Pulp from the pilot plant finisher was extracted with water using
several procedures; some of the water extracts were concentrated in a small
evaporator. Samples of water extracts and concentrates were canned, frozen,
and stored at -80F. These products, together with similar samples obtained
from several commercial plants, are being examined to determine the amounts of
sugars, acids, and other constituents that may be obtained by water extraction
of orange pulp. Some of the concentrated water extracts were added to orange
concentrate prior to freezing to determine the effect of the use of such ex-
tracts on the flavor and other characteristics of this product, both initially
and after storage.

Preliminary results indicated that a promising procedure for the water
extraction of solids from orange pulp was that of adding water to the pulp from
the finisher, immediately heating the slurry in a tubular pasteurizer at 1950F.
and then removing the excessive amounts of insoluble solids by another finisher,
set only moderately tight. Such a process would have the advantages of sim-
plicity, rapidity, hot extraction of solids, and reduced microbiological and
enzymic problems. (R. W. Olsen, R. L. Huggart, and F. W. Wenzel.)

Effect of Dielectric Heat on Some of the Constituents of Orange Juice. -
In using dielectric heat to concentrate Valencia orange juice to 420 Brix and
also when high density orange concentrates of 700 to 800 Brix were made, no
destruction of either pectinesterase or microorganisms attributable to this pro-
cess was found; the use of dielectric heat was not detrimental to the flavor,
ascorbic acid, or cloud of the juice. No significant differences in results
were found when the same 500 Brix Valencia concentrate was further concentrated
to 800 Brix using either dielectric or steam heat; there was a trend for con-
centrates withdrawn from the evaporator at different degrees of concentration
to be slightly less viscous when dielectric heating was used. At the request
of Mr. Ralph Sargeant, the dielectric equipment and the assistance of Mr.
H. C. M. Longacre were made available for this investigation by Sylvania
Electric Products, Inc., New York, N.Y. The equipment consisted of a 10-kilowatt
dielectric generator that was operated by Mr. Longacre at a frequency of 15
megacycles and with a drop of 25 volts across the electrode. (F. W. Wenzel,
C. D. Atkins, A. H. Rouse, E. L. Moore, Roger Patrick, E. C. Hill, R. W. Barron,
and G. H. Ezell.)

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 1 10/2/58 FWW


Citrus Vinegar. The brown sediment that appears in citrus vinegar after
storage was found last year (1957 Ann. Rept., p. 237) to be spent commercial
pectic enzyme preparations used for hydrolyzing the pectic substances present.
By using these preparations, an initially crystal-clear vinegar could be ob-
tained that was readily filtered. Pectic enzymes available from a number of
different manufacturers were tested for sediment formation. Only one out of
eleven tested did not produce sediment on storage of the vinegar made in their
presence. The one enzyme preparation was deficient in the enzyme, naringinase.
Vinegar made from grapefruit with this enzyme preparation would be expected to
be bitter. However, a year-old vinegar made from ground, whole grapefruit
without the addition of pectic enzymes was not bitter even though relatively
large amounts of naringin were found to be present by chromatographic analysis.
Suppression of the bitterness of naringin by organic acids has been confirmed
by tasting naringin solutions containing various amounts of acetic and citric

A number of filter-aids were investigated to see if a haze-free vinegar
could be obtained by their use during filtration when no pectic enzyme prep-
aration was used. No improvement in clarity took place except with a mixture
of bentonite and Celite, A satisfactorily clear product was obtained using
this mixture, but only when the latter was finely dispersed in the liquid before
filtration. A Waring Blendor or homogenizer was necessary to give the needed

It was found also that the spent enzyme material that forms sediment could
be removed by treating the liquid with activated carbon at near boiling tempera-
ture, followed by filtration. This treatment was best carried out before the
acetification step since similar treatment of the finished vinegar removed most
of the characteristic flavor and aroma.

Several alternative paths to the preparation of clear, citrus vinegar are
now available: (1) the use of a sediment-forming enzyme followed by its removal
with activated carbon, (2) the use of a non-sediment-forming enzyme preparation ,
and (3) the use of no enzyme preparation followed by clarification with bentonite-
Celite mixture. The preferred path would be that of least expense. (R. R.

Inositol in Citrus Fruits. These investigations have been continued with
the principal emphasis being directed toward the development of a satisfactory
economical method for the extraction and recovery of myo-inositol from citrus
peel, juices, and processing or by-product liquids.

The two principal raw materials used this year have been the filter press
waters.from both orange and grapefruit peel used in the recovery of hesperidin
and naringin, respectively, and distillery slops from the manufacture of citrus
alcohol. In both cases these liquids are waste materials differing, primarily,
in their sugar concentration with the latter having a negligible sugar content
and a high concentration of glycerol produced during the fermentation.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 m 10/2/58 FW


The precipitation of inositol from filter press water employing the ammoni-
acal lead acetate procedure has been studied quite intensively. It was con-
cluded that approximately 50 percent of the inositol that was precipitated was
completed with the lead, while the remaining 50 percent was held by occlusion.
The amount of inositol occluded was certainly influenced by the total solids
content, including constituents other than inositol which were precipitated by
lead in the presence of alkali. The inositol was then carried out of solution
by the heavy precipitate.

The filtrates from the treatment of the lead precipitates in water slurry
with sulfur dioxide required further purification prior to crystallization of
the inositol. These solutions, after evaporation to dryness, could be extracted
with dry pyridine which would remove interfering substances and leave the
inositol insoluble. Inositol then was readily crystallized from aqueous solutions
of the pyridine insolubles. This general procedure was also found to be appli-
cable to concentrated aqueous solutions. In this case the pyridine-water azeo-
trope formed was distilled off until all of the water had been removed leaving
pyridine soluble and insoluble fractions. Likewise, inositol could be isolated
from the pyridine insoluble fraction, because practically all the sugars and
amino acids were removed by the pyridine. This process was also carried out on
filter press water after concentrating to 650 Brix and on 360 Brix concentrated
citrus alcohol distillery slops without prior precipitation with lead acetate.
Isolation of about 50 percent of the total amount of inositol was possible by
this procedure.

The use of methanol and isopropanol for the direct precipitation of the
distillery slops showed widely different results. With methanol the inorganic
salts were precipitated leaving the organic constituents, including inositol in
solution. The isopropanol caused precipitation of practically all the organic
and inorganic material. Precipitation with a 50-50 mixture of these alcohols
caused precipitation of approximately 50 percent of the inositol, while all of
the glycerol and most of the residual glucose remained in solution. The amount
of inositol precipitated was increased about 10 percent by stepwise precipitation
of the slops with methanol followed by the addition of isopropanol to the metha-
nol-water filtrate in an equal volume.

All of the above methods have served, primarily, for the isolation of myo-
inositol in crude solutions of small volume compared to the original dilute
solutions. However, the recovery of crystalline inositol from the crude solu-
tions still exists as a difficult problem to be solved if an economical process
is to be evolved. (R. W. Wolford.)

Production and Use of Activated Citrus Sludge. A study to determine the
potential of excess activated citrus sludge as an animal feed supplement was
continued. Fifteen samples of activated sludge, prepared on a laboratory scale
activated sludge plant, were analyzed for vitamins of the B group and for pro-
tein. Some results were previously reported (1957 Ann. Rept., p. 235) and the
completion of the analyses for niacin and riboflavin concluded this study.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 n 10/2/58 FWW


The niacin content of the sludge samples ranged from 7.65 to 12.10 micro-
grams per gram and the riboflavin from 18.68 to 37.60 micrograms per gram.
Neither the amount of cobalt used as a nutrient nor the method of drying had
any noticeable effect on the niacin or riboflavin contents. The addition of
nitrogen as a nutrient increased the production of both niacin and riboflavin.
The addition of phosphate caused a decrease in riboflavin but an increase in

The results indicate that excess sludge does contain appreciable amounts
of B-group vitamins and large amounts of protein. Its principal value as a
feed supplement for most animals would be in its protein content. As a chicken
feed supplement, the value would probably lie more in its vitamin B12 content.
(M. H. Dougherty.)

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
869 o 10/2/58 FWW