UNIVERSITY OF FLORIDA
Agricultural Experiment Station
THE UTILIZATION OF CULL CITRUS
FRUITS IN FLORIDA
Summarized by SiET1 S. WALKER from
the original monograph by
F. ALi x. McDERMOTT
The Station Bulletins w ill be enl fr'e upton free fiction to the Experinene
Station, Gaines illk.
The problem of utilizing cull citrus fruits has been discussed
and studied for many years. A large amount of investigational
work has been carried on by the U. S. Department of Agricul-
ture, by private and public enterprises in California, and, to a
greater or lesser extent, in Florida. A great many attempts
have been made to utilize cull fruits; some of them have been
successful. In October, 1911, arrangements were made with the
Mellon Institute, in cooperation with the Florida Citrus Ex-
change, whereby Mr. F. A. McDermott received the appointment
to a fellowship to work on the problem of utilizing cull citrus
fruits. Mr. McDermott continued his studies until August,
1913. At the close of his work he wrote up the results of his
investigation in an extended thesis. This was i,.:i_-.,I to the
Florida Experiment Station for publication in March, 1916.
Owing to the length of the thesis it seemed impracticable to
publish it in the original form. In the fall of 1916, Mr. S. S.
Walker, Associate Chemist to the Experiment Station. was au-
thorized to prepare a manuscript from the original thesis. This
has been submitted tq Mr. McDermott, who consents to its
publication in this form.
Since the preparation of this manuscript, Mr. Walker has
resigned his position as Associate Chemist, to take up work
with a private enterprise in the utilization of citrus by-products.
The thanks of the institution, and of the citrus-growing people
of the State are due Mr. McDermott for this excellent piece of
work, and Mr. Walker for preparing it in form for publication.
P. H. ROLFS,
THE UTILIZATION OF CULL CITRUS FRUITS IN FLORIDA
Every year the citrus fruit growers of Florida suffer a con-
siderable loss on account of the cull fruits which are not suitable
for shipping. This loss often amounts to as much as ten per-
cent of the fruit coming into the packing house. The chief
reasons for the existence of culls are superficial defects which
in no way injure the value of the fruit for immediate consump-
tion or for preservation. Since the local market cannot take
care of this large amount of cull fruit, it is very desirable to
find methods of preserving or otherwise utilizing it.
With these facts in mind, the Florida Citrus Exchange sev-
eral years ago endowed a fellowship in the Mellon Institute of
Pittsburg, Pa., for the purpose of studying methods of utilizing
cull citrus fruits. Mr. F. Alex McDermott was appointed to the
fellowship and worked on the problem of cull utilization from
October 17, 1911, to August 31, 1913. His work has been re-
corded in great detail, but up to the present time has not been
made public except for a very brief summary of it, which was
read before the Annual Citrus Seminar at Gainesville in Oc-
This bulletin is a more extended summary of the work than
the one read at Gainesville and includes much detailed descrip-
tion of the actual laboratory manipulations. Since these details
will probably be of interest to only a few readers, they have
been printed in small type. The casual reader can omit the
small-typed passages and still get a comprehensive idea of the
work as a whole.
It should be understood that the writer neither claims nor
accepts any responsibility for the facts presented, but that the
entire credit for the work belongs to Mr. McDermott.
Certain factors must be considered carefully before any cull-
utilization project can be successful. In the first place, opera-
tion on a small scale is certain to be proportionately more ex-
pensive than operation on a large scale. This means that co-
operation between the cull-utilization plant and a large number
of growers or packing houses is essential. Likewise, the scope
of the plant-that is, its range of products-must not be too
limited. Will, (J. Ind. and Eng. Chem. 1916, Vol. 8, p. 78) has
pointed out the dangers of one-sided production and attributes
the failure of many California citrus by-products plants to this
Buelltin 135, Utilization of C'll Citrus Fruits
cause. At the same time it is quite possible to go to the other
extreme, especially when the plant is just getting started, and
attempt to manufacture a greater vaNriety of products than can
be successfully handled.
AMr. ?McDermott's investigations fall naturally under four
main heads. They are:
L The Preservation of the Juice:
(A) In its natural concentration;
II. The Preparation of Oil from the Peel:
Extraction, expression, and distillation.
III. The Preparation of Alcohol.
IV. The Preparation of Citric Acid.
The work done on these various problems will be taken up
1. PRESERVATION OF THE JUICE
4A) 'Il'HE .III
It has long been known that the preservation of orange juice
in a permanent and palatable form is a difficult proposition. A
great many fruit juices can be preserved by simple pasteuriza-
tion at low temperature, but this is not sufficient for orange
juice. Orange juice which was pasteurized, at either high or
low temperature, usually kept only a few weeks before it turned
dark in color and acquired an offensively acrid taste, and where
high temperature was used there was the additional disadvan-
tage of an unpleasant cooked taste. Since this cooked taste
could be avoided by using less heat, the problem resolved itself
into finding the cause and means of prevention of the discolora-
At first heat resisting micro-organisms were suspected and
many experiments were made to isolate and identify them.
Bouillon and gelatin media were inoculated with juice which had
darkened after pasteurization and also with juice immediately after pas-
teurization. As a general rule 'rowths were not obtained with specimens
of juice which has been heated to GOC. or above; in one or two isolated
cases, bouillon cultures showed the presence of the species of wild yeast
a strain of Willian anomala-which grows regularly on untreated orange
juice and which is responsible for the development of the perfume-like "
odor which is noticed about orange juice after it stands some hours with-
out treatment. The organism was constantly present upon oranges and
was probably always present in the air of the room, to some extent, and
its appearance thus in isolated cultures was most probably due to acci-
Florida AgricWultral E'peri'ment Station 133
An interesting point in this connection is that all attempts to grow
upon sterilized orange juice the blue-molds (Pc)nicillinti italicmii and I'.
olict'ceetlit), common upon citrus fruits, resulted instead in the growth of
this WTillia with two or more accompanying bacteria. There seems to be a
general impression that the preservation of orange juice is largely a ques-
tion of preventing the growth of these blue-molds in the juice. As a
matter of fact it seems probable that these molds will not ordinarily grow
readily upon orange juice, perhaps on account of the acidity of the medium,
but that the molds which are occasionally found upon orange juice are
really species of Wehmner's oenus Citrno cc~s. or some of the PcIictilli
more resistant to acid.
But the theory that darkening was caused by micro-organ-
isms was soon abandoned because it was found that the juice
was usually sterile after heating to only 60 C.; moreover those
samples which were pasteurized at higher temperature appeared
to deteriorate and darken even more than those which had re-
ceived less heat.
In view of these facts it seemed most likely that the darken-
ing was caused by some spontaneous chemical change takin,
place in the juice, probably an oxidation.
Enzymes of the oxidase and peroxie ae cl ass l i'rteqiu ny the can
of such changes in fruit i)poducts. Tests for thee bodies Ihowed that
peroxidaIi e was 'present in the peel and seeds of the orange, but not iln ith-
juice. In fact, it was found to be totally unable to withl:tand an acid
reaction and that as little as 1 cc. of orange juice added to 10 cc. of acti e
peroxidase solution was sufficient to destroy its activity completely. The
peel also contained a catalase and a very active invertase, but they could.
not be detected in the juice.
Since no oxidizing enzymes were found in the juice. it was
thought that the darkening must be due to a simple process tot
autoxidation which could be prevented by preserving the pas-
teurized juice out of contact with oxygen (air). One of the
simplest methods for accomplishing this would be to replace all
of the air dissolved in the juice, as well as that above it, by
some inert non-oxidizing gas such as carbon dioxide, hydrogen,
or nitrogen. Accordingly, a series of tests was carried out to
investigate this possibility. The preliminary tests carried out
with small amounts of juice in test tubes, showed that darken-
ing could be entirely prevented by saturating the juice with
carbon dioxide and replacing the air above the juice with that
gas; that hydrogen could be used in place of carbon dioxide,
altho it was much more difficult to handle; and that the nitrogen
used (which contained 7 percent of oxygen as an impurity)
could not be substituted for the pure carbon dioxide, altho it
decreased the amount of darkening somewhat. Incidentally, it
134 Bulletin 135, Utilization of Cull Citrus Fruits
was shown that a temperature of 63 to 65C. for 15 to 30
minutes was the most satisfactory condition for securing com-
plete sterilization, with a minimum of the objectionable cooked
These preliminary tests were followed by a more extended series, using
50 cc. quantities in small narrow-mouthed bottles. Several methods of
treatment were tried. The first was to warm the juice slightly in a cur-
rent of the gas with which the test was being made; then while the cur-
rent of gas was maintained, the juice was cooled with ice water, run into
the bottles, the air driven out of the space above the juice with the gas,
the bottles stoppered, the stoppers tied in, and the whole pasteurized.
After pasteurization, the necks and corks were dipped in melted paraffin.
Later tests were made in which the removal of the dissolved air was
effected by means of a vacuum, and also by passing the gas thru the juice
without warming. Usually twelve bottles were prepared in a set; these
were then kept under observation for some time, specimens being occa-
sionally opened and tasted. The details of some of the tests are as follows:
Series A: Dec. 16, 1911.-Juice heated to 60C. while passing CO2,
cooled to room temperature, bottled in CO,, and set in ice box over night;
next day run into small bottles (previously sterilized), air removed by COz,
bottles closed with paraffined stoppers, tied in, and pasteurized at 60'C. for
20 minutes. Aside from precipitation of suspended matter and a slight
darkening, these specimens had undergone no serious change up to June
Series C: Dec. 19, 1911.-Duplicate of Series A, except that a tempera-
ture of 70C. was used both for the initial treatment with CO,, and for
pasteurizing. The juice kept equally well, but the high temperature injured
Series D: Dec. 20, 1911.-Duplicate of Series C, except that a tempera-
ture of 80'C. was used. The flavor was badly impaired; also after long
standing the color became darker than in Series A, tho not as dark as
specimens pasteurized in air.
Series F: Dec. 22, 1911.-In this series nitrogen was used containing,
as before stated, about 7% oxygen. Pasteurization was done at 70*C.
Darkening set in after about 4 weeks, and all were quite brownish at the
end of 6 weeks.
Series G: Dec. 28, 1911.-Juice was saturated in the cold with CO., in
pressure ("soda") bottles, closed when full of gas and pasteurized at 60'
to 65C. for 20 minutes. Had retained good color and taste up to June 24,
1913. The CO., however, gave it a slightly unnatural tang.
Series H: Jan. 1, 1912.-Juice was heated in an open beaker to 60'C.
and then cooled in ice water in a CO, stream, placed in small bottles, sealed
and pasteurized at 70" to 75'C. for 15 minutes. The samples became some-
what darker than those of Series A, but not as dark as in Series F.
Series I: Jan. 2, 1912.-The juice was exhausted and the vacuum re-
leased by the admission of hydrogen; container and juice then cooled in ice
water, the juice placed in small bottles, the latter filled with hydrogen, stop-
pered and pasteurized at 70' to 75C. for 15 minutes. Both color and taste
kept very well.
Florida Agricultural Experiment Station
Series N: Jan. 8, 1912.-Juice was heated to 60C. in an open vessel
in a current of CO2, cooled to 10C. in this gas, bottled in it, and pasteurized
at 600C. for 30 minutes. This series kept very well.
Series S: Jan. 19, 1912.-Juice was first warmed to 55'C. and cooled to
10C. in a hydrogen stream, in bottles. Pasteurized for 30 minutes at 60"C.
The specimens kept quite well, altho darkened slightly. Taste rather better
than with CO, specimens.
Series U and V: Feb. 8 and 9, 1912.-These two series contained juice
of the same lot of oranges, but in series U all air was replaced by CO2, while
series V received no gas treatment. Both sets were pasteurized at 63 to
65C. for one hour on each of two successive days. Series U kept all right
while Series V began to darken 13 days after pasteurization and later de-
veloped the full discoloration characteristic of juice pasteurized in air.
Series W: Feb. 27, 1912.-Juice was saturated with CO0, but was
pasteurized (at 70 to 75C.) in bottles from which the residual air had not
been displaced. Darkening was complete in a month.
The specimens of preserved juice were not kept under any
special conditions of light or temperature, but they retained
their appearance and taste unimpaired for over 18 months and
gave every indication of being permanent. When large bottles
of juice were pasteurized it was found best to heat for the full
While most of the work was done on orange juice, it was
found that grapefruit juice was subject to the same sort of
discoloration and change of flavor and that the same measures
could be used to prevent it.
Some study was also made of the flavor of juice expressed
from whole, unpeeled fruit, using a press which crushed the
peels considerably. The presence of a certain amount of flavor-
ing from the peel adds greatly to the pleasant taste of orange
juice. It was found that the most desirable flavor was obtained
by leaving about one-tenth of the oranges unpeeled. In the
case of grapefruit, however, it is necessary to peel all of the
fruit on account of the bitter glucosides contained in the peel.
One difficulty in all of the work with citrus fruit juice arose
from the fact that whenever the juice came in contact with iron
it attacked the metal and acquired a bad taste from it. Ex-
periment showed that tin, copper, bronze, brass, nickel, and
even silver were attacked with a similar result. Solid aluminum
proved to be the most satisfactory metal to use for pans and
other apparatus for which it is mechanically suitable. Altho it
too is acted upon by the juice to some extent, it is tasteless and
harmless in the small quantities which dissolve. Glass, por-
celain, and enameled ware are also suitable for use in handling
citrus fruit juices.
136 Bulletin 135, Utilization of Cull Citrus Fruits
Another serious mechanical problem was met in attempting
to clarify the juice. Citrus fruit juices contain large quantities
of gelatinous material in suspension, and this material effec-
tually closes up the pores of any ordinary filtering medium, so
that filtration is entirely too slow for commercial purposes. A
great variety of filters, including power-driven presses, was
used but'the results were not satisfactory.
When the juice was poured on an ordinary filter of paper, cloth, or
brewers' mass, a small amount ran thru rapidly at first, but the rate rapidly
diminished with corresponding increase in clearness of the filtrate. Suction
increased the speed to some extent, but not enough to make the method prac-
ticable on a large scale. Filters of sand and fuller's earth yielded almost
water-clear filtrates but the rate was very slow. The same was true to a
greater or less extent of Norton Alundum, Tripoli stone, Berkfeld and Pukal
filters. The best results with suction filters were obtained by using a mat oI
sand mixed with asbestos fiber supported on cloth. With this arrangement
filtration could be hastened by occasionally stirring up the surface of the nma
Filter-press filtration was next tried, using a small press and a pr'es'uIre
of 150 to 200 lbs. per square inch. But all the filteiing media tried-pape i
cloth, and brewers' mass-.promptly clogged and stopped the flow.
Clarification of the juice by fi, it .,l I.. also proved un-
satisfactory. Centrifugal filtration, however, seemed to offer
a possible solution of the problem. After some preliminary lab-
oratory experiments it was found that a fairly satisfactory cl;tr-
ification could be effected by using a combined centrifu,(n
clarifier and filter of the DeLaval type. On account of the large
amount of suspended solids, it is recommended that the juice
first be put thru a simple centrifugal clarifying bowl (which
consists of one of the combined clarifiers and filters with the
filtering mechanism omitted) which will remove the greater
part of the suspension. For continuous working, two machines
would have to be provided, one being used as a simple clal i;f ;,
bowl while its filtering material was being removed and washed;
thus each machine would serve alternately as simple clarifier
and as combined clarifier and filter.
Since the original work was done, a type of very high speed
centrifuge has been placed on the market, which, it is said, can
be used with satisfactory results on citrus fruit juices, yielding
a nearly clear product.
In order to obtain commercial quantities of perfectly clear
juice it seems necessary to resort to the practice used in wine
manufacture-that is, storage until the solids settle out. This
would involve considerable expense for storage vessels and a
long delay (at least 6 weeks).
Florida A-gricult'ral Experiment Statiou
After it was discovered that discoloration of the juice could
be prevented by replacing the air with a non-oxidizing gas, it
was thought that the same result might be accomplished by
sealing the juice in a vacuum. Laboratory experiments, using
small glass sealing bottles, indicated that this was the case.
Afterward a small apparatus was arranged by means of which
samples of juice could be sealed in vacuum in ordinary glass
containers. A number of jars of orange juice were sealed in
this way and for the most part they kept quite well.
Altho the work thus far reported showed clearly that the discoloration
uf citrus fruit juice could be prevented by excluding oxys'en, it still failed
to show the exact cause and nature of the discoloration. In order to throw
further li'ht on this question many other experiments were carried out.
Various combinations of orange juice and orange-juice constituents were
prepared in different ways and treated by different methods. The effects ol
a large number, of chemicals and artificial preservatives were investigated.
Hydrogen peroxide in considerable quanttities did not entirely prevent dis-
coloration or fermentation. Sodium benzoate (0.1', ) preserved the jinia:
quite well; some fermentation occurred. however. Salicylic acid ,,.l',
produced sterilization but did not preserve the color. The same was true i,
chloroform and formic acid. Formaldehyde I 0.1';) preserved both sterility
and color, but is, of course, objectionable. Toluene. acetone, and thymol all
failed to prevent darkening. Hydrofluoric acid and sulphur dioxide 1;oth
preserved the juice quite well, altho darkening' was not entirely prevented.
Increasiing- the amount of citric acid did not have any effect; neutralizini-
the acid did seem to prevent darkening' in some cases, iut juice rendered.
alkaline darkened rapidly.
Considering' all of the evidence available it seems quite probable that thI
darikeniinL is the result of autoxidation, possibly as the result of some enzitme
action, in sterile solution, of some normal constituent of the orange juice.
A few experiments were made in an attempt to discover a method ol'
cold sterilization other than by using chemical antiseptics. The methods
tried consisted of treatment of the juice with ultra-violet light and with a
weak electric current. Neither of these methods, however, gave satisfactory
(R) THE (CON)CNT'IR'ATED .11 I1CE
Experiments were next undertaken along the line of con-
centrating the juice. In general there are two methods for
accomplishing this, by vacuum evaporation and by freezing out
the water. Mr. McDermott's work was confined to the evap-
After preliminary trials with various types of vessels some
experiments were made in the laboratory of the J. P. Devine
Co., at Buffalo, N. Y. Here it was found that using a vacuum
of 27.5 to 28 inches and a temperature of only 50WC., in a
steam-jacketed copper pan, as much as 3.5 gallons of juice to
138 Bulletin 135, Utilization of Cull Citrus Fruits
each square foot of heating surface could be evaporated in an
hour, approximately 85 percent of the weight of the juice being
removed. The required heat was obtained from steam at less
than one pound pressure. However, the juice concentrated in
this copper pan had a very undesirable metallic taste and dark
color, and the remaining tests were made in a special solid
aluminum pan, also heated with steam.
An important point brought out by this work was the ne-
cessity of keeping the temperature as low as possible in order
to avoid injury to the taste. It was found that, altho 50C. was
not high enough to cause injury, it was difficult to avoid over-
heating around the outside layers of the concentrated mass, and
hence an indicated temperature of 40 to 50C. was much safer.
For this same reason it is better to concentrate to only about
20 percent of the original volume, altho it is possible, with care,
to evaporate to 15 percent.
The presence of suspended matter in both orange and grape-
fruit juice constitutes a chief difficulty in all concentration
work, and the more thoroly the juice is clarified the more read-
ily is it concentrated. In the case of grapefruit juice, however,
there is normally a smaller amount of suspended solids than in
orange juice, and it is therefore practicable to concentrate
grapefruit juice to as low as 12 percent of its original volume.
It was found that the concentrated juices were subject to
the same discoloration as the fresh ones, but that it could be
prevented by the same method, viz., sealing in absence of oxy-
gen. It has been found by other investigators that concentrated
lemon juice will keep without pasteurization, on account of its
high acidity. One might expect that this would also be the
case with orange and grapefruit juices. Mr. McDermott's ex-
periments along this line were not extended enough to be con-
clusive but they indicated the probability that concentrated
orange juice cannot be relied upon to keep without pasteuriza-
tion; grapefruit juice, on the other hand, will very probably
keep under these circumstances, even when diluted with a small
amount, one-fourth, or less, of orange juice.
One disadvantage of the concentrated juice is that it is
necessary to add flavoring after concentration, as the vacuum
process removes nearly all flavoring materials from the juice.
(C) THE PREPARATION OF DRY JUICE
Considerable work was done along the line of preparing a
dry product from orange and grapefruit juice. It was found to
Florida Agricultural Experiment Station
be perfectly possible to produce a dry powder, but on account
of the inordinately long time required, as well as certain dis-
advantages inherent in the powder itself, it did not seem to
be commercially promising.
II. THE EXTRACTION OF OIL FROM THE PEEL
Next to the utilization of the juice of citrus fruit the ex-
traction of the oil from the peel is the most important phase
of the cull problem. On account of Italian competition, the
problem of manufacturing citrus oils in the United States is
limited to mechanical processes handling large amounts of peel
at low cost. Three fields are open; solvent extraction, pressure,
It would appear at first that some process of solvent extrac-
tion would offer the best chance of usefulness. The objection
to any such process, however, is that the solvent is likely to
extract a number of things that are undesirable, such as resins,
bitter glucosides, excess of pigment, etc.
Extraction experiments were tried with petroleum ether, chloroform,
carbon tetrachloride, acetaldehyde, and also with mixtures of solvents. On
the whole the best results were obtained with carefully washed petroleum
ether (washed to remove as much as possible of the strong gasoline-like odor).
The flavor of these extracts was quite good, but they had the disadvantage
of being strongly colored, and it was very difficult to remove the last traces
of the solvent from the extract. It was found possible to accomplish this
last result to a fairly complete extent by treating with a small amount of
alcohol and warming slightly while evacuated. While the oil thus extracted
was superior to that prepared by the use of chloroform, carbon tetrachloride,
or ether, it was not as good as the imported article. The acetaldehyde dis-
solved too much substance from the peel, and the extract presented both
aqueous and oily particles, which were very hard to separate; after separa-
tion, the oil proved to be of inferior quality.
Accordingly, attention was next turned to methods of ex-
traction by pressure. Two forms of mechanical expression
seemed possible: (1) Between rollers held tightly together by
powerful springs; and (2) squeezing in a hydraulic or screw
The roller experiments were carried out by passing quar-
tered peels thru a heavy clothes-wringer. While this method
gave some promise of success it was discontinued in view of
more desirable developments.
With a screw press some very good oil was obtained, but its
keeping qualities were poor and the yields were far from satis-
Bulletin 1J5, Utilization of Cull Citrus Fruits
The distillation method still remained to be tried. It has
long been considered, and so stated in the literature, that
" rectified citrus oils are decidedly inferior in quality. How-
ever, some preliminary work done by Mr. McDermott indicated
that the distillation method contained possibilities, and further
experiments were undertaken.
The first of the preliminary work was done by distilling in a current of
alcohol vapor (from 50e alcohol). The distillate was a milky emulsion,
with a very pleasant odor and favor of fresh orange oil.
An apparatus was next arranged in which the ground peel was placed in
a long cylindrical tube which was preheated by being entirely surrounded
by the vapor of the boiling alcohol, thus diminishing condensation in the
peel; 95'; (commercial) alcohol was used in this case. The distillate
consisted of two layers, the upper being' limonene from the oil, and the lower
a dilute alcohol containing' most of the flavorings materials from the oil. At
first this alcoholic layer w as not clear, but on separation from the limonene,
and filtering, thru paper, it became clear. At this pint its taste was iot
entirely pleasant, but oin standing for about two days, a small hnm of oil
separated out, and on -removing this, a clear alcoholic solution remained,
having a very pleasant flavor of orange. About an equal volume of alcohol
was foul to have condensed in the apparatus and this was drained off anid
filtered; it corresponded fairly well to an ordinary alcoholic extract of ich
peel. 1y1 mixing equal volumes of these two extracts, a very good orange
llavorinx' was prepared.
Distillation with steam under reduced pressure was next tried, using
the apparatus described above, and a good yield of oil of excellent icvality
The final, most satisfactory method of distillation found
was as follows: A vacuum pan was equipped with a piece of
lead pipe run in thru a tight joint at the side near the top, and
coiled in the bottom, the coiled portion being perforated with
many small holes. A piece of wire gauze was placed over the
coil to protect the holes from clogging, and the ground peel was
placed on top of the gauze. The outer end of the lead pipe was
connected with a small steam generator capable of withstanding
a vacuum; the cover of the vacuum pan was clamped on tight
over a rubber gasket, and the outlet pipe was connected with
a tin coil condenser and receiver. The whole system was ex-
hausted by means of a rotary vacuum pump. As soon as the
vacuum had reached approximately 25 inches, as indicated by
a mercury gauge, heat was applied beneath the steam generator,
and by the time the vacuum had reached 27.5 to 28 inches,
water vapor was coming off regularly from the generator and
shortly afterward had passed thru the column of ground peel
and began to condense and collect in the receiver. The first
portion. of the distillate usually consisted of pure oil; this wax
very oon accompanied by a small amount of water, which in-
creased. rapidly until after about five minutes, the water was
decidedly in excess. It was found that for the purpose of
distillihn as much of the oil as possible in the shortest practi-
cable time. it is best It distribute the ground peel in the form of
a long cylin(rical column: as the water vapor passes up thi.
colu mn it appears to become more and more saturated with the
oil vapor and thus by far the greater part of the oil is removed
in the first few minutes of distillation.::
The oil thus obtained by Mr. McDermott was accompanied
by a large volume of water which was removed by means of a
separatory funnel and the oil filtered once thru paper. It was
quite clear and colorless; its flavor was iver sweet and pleasant,
and actual experiment proved that it was an excellent !!- n-:
material when dissolved in alcohol. The yield was about 4.5
ounces of oil from a box of 150 Valencia oranges, and about
half that quantity from other varieties of oranges. The essen-
tial point in securing a good yield is to break every oil cell in
the peel and to distill as soon as possible after grinding.
Incidentally it -was found that peels which had been allowed to dry out
over night, or even longer, before grinding, usually yielded a much larger
amount of oil than d(id peels when ground fresh. Apparently the spongy
under-layer of the peel does not absorb and hold the oil so tenaciously when
ground dry as when grIound fresh. However, drying' before a fan over night
was too rigorous and cut down the yield; drying before a fan after grinding
the peel reduced the yield of oil to zero.
The distilled oil was colorless whereas the market demands
a yellow oil like the hand-pressed Italian article. This defect
was easily remedied by percolating the colorless oil thru a small
amount of the yellow outer peel which had been removed from
an orange and ground up. If alcohol is added to the oil as a
preservative (see next paragraph), it is usually better to color
the oil after addition of the alcohol.
Orange oil does not keep well when exposed to light and air
at ordinary temperature and a number of methods have been
proposed by various investigators for preventing deterioration.
The addition of five to ten percent (by volume) of absolute
alcohol proved quite effective as did also the use of carbon
dioxide applied in much the same way as recommended for
preserving juice. In any case, small dark-glass containers
Patent for this process has been applied for.
hNoWdo .4g4cnIt"M fArocKnicnt Statim,
Bulletin 135, Utilization of Cull Citrus Fruits
should be used, and cold storage if possible, the entire contents
of the bottle to be used soon after opening.
An oil practically identical with orange oil was obtained
from grapefruit peel, but the yield was very much smaller.
In connection with the manufacture of oil, the method of
peeling the fruit becomes an important factor. So far as Mr.
McDermott's investigations went, the most practical solution of
the problem seemed to lie in the employment of a number of
boys provided with knives of a special design (see page 23 of
the booklet The Juicy Joys of Florida Fruits" published and
distributed by the Florida Citrus Exchange). In considering
the production of orange oil, attention is called to U. S. Depart-
ment of Agriculture Bulletin No, 399, by Hood and Russell, on
Ill. THE PREPARATION OF ALCOHOL
Since orange juice contains from 8 to 10 percent of easily
fermentable sugar, it is a good source of alcohol. While it
would probably never pay to use for this purpose fruit which
was fit for human food, still the drops and decayed fruit could
be used for the manufacture of alcohol.
Several experiments were made on the fermentability of the juice. In
the first experiments about 5 or 10 liters of juice were neutralized with
calcium carbonate, heated in a retort to the boiling point, small amounts oa'
magnesium sulphate and potassium phosphate added, and the juice boiled
rapidly for about fifteen minutes. The juice thus sterilized was cooled to
room- temperatue, inoculated with bakers' yeast at the rate of 20 grams
per liter, and allowed to ferment for from three to six days. The alcohol
was then distilled and about 1 liter of crude spirits was collected from 5
liters of original juice. This crude liquor was then redistilled several times,
using a Glinski distilling column, until a concentration of 94%( by volume
was reached. In several runs the fruit used was badly spoiled, but the yields
were always essentially the same, viz., about 50% of the sugar orig-
inally present. This is as good as is ordinarily obtained in the manufacture
of alcohol. A mixture of orange and grapefruit juices fermented and yielded
alcohol just as well as did either juice separately.
Further experiment showed that it was not necessary to neutralize the
acid of the juice before fermenting, altho the fermentation process was
somewhat slower than in neutralized juice. The addition of the salts above
referred to is also unnecessary.
When whole, unpeeled fruit is used for making alcohol it is necessary
to get rid of the oil of the peels since the presence of the oil greatly depresses
fermentation. This, however, is accomplished by the initial boiling to
sterilize the juice before inoculating.
Florida Agricultural Experiment Station
IV. THE PRODUCTION OF CITRIC ACID
It does not seem probable that oranges or grapefruit can
successfully compete with lemons and limes as sources of citric
acid. However, it is known that certain Penicillium-like molds
of the genus Citromiyces possess the ability to convert sugar
into citric acid when grown under proper conditions. In fact,
it appears that this process was at one time actually used in
Europe for the commercial production of citric acid.
In view of this it seemed possible that the Citronices organisms might
be grown in orange juice with a consequent increase of the acid content.
Experiment proved this to be the case and some work was undertaken along
the lines of (1) hastening the rate of growth and production of acid; and
(2) treating the medium so as to prevent the invasion of foreign organisms.
The work along the first branch was quite unproductive of results; no salts
or other agents were found which could markedly increase the rate of
growth. Along the second line some success was obtained; it was found 7hat
the Citromyc'.cs molds will grow in a medium containing 6', of sea-salt, u f-
ficient to inhibit the growth of most bacteria and many molds.
It cannot be said that this offers more than a mere possi-
bility from the commercial standpoint and it seems far better
to allow the production of citric acid from natural sources to
be restricted to those regions where lemons and limes are raised.
It should be stated, however, that in the event of the manufac-
ture of alcohol from waste juices, the spent beer from the still
might be worked up for the recovery of the citric acid originally
present in the fruit juice.
V. UTILIZATION OF THE WASTE PULP, SEEDS AND PEEL
No experimental work along this line is reported by Mr.
McDermott, but from theoretical considerations he concluded
that the refuse might have considerable value as a fertilizer or
as a stock food.
MR. McDERMOTT'S CONCLUSIONS
1. It is possible to preserve orange juice for at least
eighteen months, and probably indefinitely, by pasteurization in
the absence of air (oxygen).
2. The juice may be concentrated to about twenty percent
of its original volume by vacuum evaporation, after proper clar-
ification, the concentrated product flavored with orange extract,
and packed and preserved in the same way as the fresh juice.
3. The same facts as represented in 1 and 2 and true for
the juice of the grapefruit.
144 BHulltin 15, Utili.:tioi of COll Citrus Fruits
4. It is possible, but perhaps commercially impracticable.
to reduce the juice of the orange and grapefruit to a dry ma-
5. A flavoring oil which is entirely suitable for marketing
may be prepared from the peel of the Florida orange by distil-
lation in a current of water vapor at reduced pressure, and the
colorless oil so produced may be colored for sale by means of
the pigment present in the thin outer peel of the orange.
6. Grapefruit peel contains a very similar oil, but in such
a small amount as to render it unij,.,li'l,-, to attempt its re-
moval for the oil alone, altho some grapefruit peel may be
worked up with the orange peel.
7. The juice of decayed citrus fruits, drops, etc., may be
sterilized and fermented for the production of alcohol. The
spent beer from the still could be used for producing citric acid.
8. The production of citric acid from the waste orange
.juice, thru the action of Wehmer's Citrocynes molds, is a pos-
sibility, but hardly to be considered from the commercial stand-
point in the present state of our knowledge.
9. The residue from the pulp after the expression of the
juice, forms a product suitable for use as a stock food, but the
waste seeds, ground peel (from which the oil has been ex-
tracted), etc.. are of themselves practically valueless.