Group Title: Mimeo report series - University of Florida Citrus Experiment Station ; 57-2
Title: Possibilities for the utilization of surplus and cull grapefruit as by-products
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 Material Information
Title: Possibilities for the utilization of surplus and cull grapefruit as by-products
Series Title: Mimeo report series
Physical Description: 21 leaves : ill. ; 28 cm.
Language: English
Creator: Kesterson, J. W
Hendrickson, Rudolph
Newhall, W. F
Citrus Experiment Station (Lake Alfred, Fla.)
Publisher: University of Florida, Citrus Experiment Station
Place of Publication: Lake Alfred FL
Publication Date: 1956
Subject: Grapefruit industry -- By-products -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: prepared by J. W. Kesterson, R. Hendrickson and W.F. Newhall.
General Note: Caption title.
General Note: "July 13, 1956."
General Note: "At a recent meeting of the Grapefruit Study Committee of the Board of Directors of Florida Citrus Mutual, the Citrus Experiment Station was requested to furnish information on ways of diverting whole grapefruit into the by-products field. Accordingly, this prospectus prepared by J.W. Kesterson, R. Hendrickson and W.F. Newhall, is being submitted for your study."
Funding: Citrus Station mimeo report ;
 Record Information
Bibliographic ID: UF00072379
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74671232

Full Text

University of Florida
Citrus Experiment Station
Lake Alfred, Florida
Mimeo Report Series 57-2 July 13, 1956.


At a recent meeting of the Grapefruit Study ,
Committee of the Board of Directors of Florida C
Mutual, the Citrus Experiment Station was reque ~
to furnish information on ways of diverting who 196
grapefruit into the by-products field. According
this prospectus, prepared by J. W. Kesterson,
R. Hendrickson and W. F. Newhall, is being submit I&AR t
for your study.

Of the 7.6 million grapefruit trees in Florida (1954-55 season)

which are approximately evenly divided between seeded type and seed-
less type, seeded type accounted for 14,300,000 boxes or 41 percent

out of a total of 34,800,000 boxes, and seedless type produced

20,500,000 boxes or 59 percent of the total grapefruit. The produc-
tion and utilization of the Grapefruit crop for the past decade is

shown in Tabl'e 1.
It can be seen from these data that about 75 percent of the seed-

less grapefruit and 25 percent of the seedy grapefruit are sold in

fresh fruit channels. In grading grapefruit, reliable sources have

claimed an average of 50 percent pack out for fresh fruit on the seedy
varieties; whereas, a 75 percent pack out is obtained for the seedless

varieties. This would mean that in an average year approximately 7

million boxes of seedy grapefruit would be put through the packing

house to obtain the 3.5 million boxes sold as fresh fruit. This in
turn would leave about 7 million boxes to be processed directly from

the grove without any grade restrictions. If consumer acceptance of

grapefruit is to be improved, grade restrictions should be raised so

that only the best quality fruit is used in the fresh fruit market

Table 1 Production and Utilization of Florida Grapefruit

Crop Total Seeded Type Seedless Type All Types
Season Production total Fresh Total Total Fresh Total Total Fresh Total
(2) *(- Sales Processed Sales Processed Sales Processed
(1) (1) (1) (1) (1) (1) (1)

1946-47 29,000 3,314 9,816 7,100 6,050 10,414 15,866
1948-49 30,200 4,430 10,990 9,324 5,316 13,754 16,306

1950-51 33,200 4,133 13,187 11,c64 4,666 15,197 17,853
1952-53 32,500 4,297 11,023 13,008 4,012 17,305 15,035

1954-55 34,800 3,559 10,661 15,437 4,983 18,996 15,644

__________________________________ _______________ ______________ ______________ ________________________________ ______________

Thousands of Boxes
Florida Citrus Fruit Annual Summary, 1955.


and higher standards imposed on grapefruit designated for processing

channels. By proper grade restrictions and quality standards, only

that quality of fruit which could be sold at a reasonable profit

could be marketed either as fresh or canned product. Such a program

would produce an even greater quantity of cull fruit and would necessi-

tate an efficient and economic by-product operation for disposal


Since it is generally conceded that a surplus of grapefruit is

being grown in the State, it is interesting to note the total number

of grapefruit trees (Table 2) moved from Florida nurseries to Florida

destinations as reported to the nursery inspector, State Plant Board,

Gainesville, Florida. While the majority of these plantings are to

pink and red varieties (75-80%) the white seedless (15-20%) and white

seedy (5-10%) are still being planted. It is generally accepted that

the pink and red varieties are not suited for processing. In view of

the increased production of these varieties and the possibility that

it might not increase total fresh sales, it further points up the
necessity of a by-product outlet for grapefruit.

As a matter of interest, the annual packs for both frozen and

canned Florida grapefruit are shown in Table 3. The data indicate that

the consumption of canned grapefruit juice has remained fairly constant;

whereas, the consumption of blended juice has declined and the con-

sumption of grapefruit segments has increased. It is noteworthy that

frozen orange concentrate has shown increasing consumer demand whereas

the demand for frozen grapefruit concentrate has lagged. A possible

explanation may be that too much sub-quality fruit such as packing

house eliminations and June bloom fruit has been processed. The fact

that grapefruit is not always processed at optimum maturity because

Table 2 Total number of Grapefruit trees planted from 1945-1954

Total No. of Trees










(1) Florida Citrus Mutual Annual Statistical Report

- IrfI











Table 3. Florida Production of Grapefruit Products.

Canned 1Grapefruit Products Frozen Grapefruit Prod.
Grapefruit Grapefruit Blended Grapefruit Blended
Season Juice Segments Juice ..' .Juice Juice
(3) (1) (1) (1) -- (2) (2)

1945-46 15,089 2,407 12,267
1946-47 8,583 5,098 10,034 -
1947-48 7,987 3,158 11,894 1 -

1948-49 8,843 4,238 10,252 116 112

1949-50 7,894 3,379 6,768 1,585 1,303
1950-51 12,742 4,628 8,797 188 254
1951-52 8,731 3,405 6,396 1,098 535
1952-53 10,853 3,814 5,707 1,159 480
1953-54 14,882 4,332 6,402 1,656 965
1954-55 10,027 6,c68 3,971 1,155 561


1000 Cases of 24 No. 2 cans
1000 Callons
Florida Citrus Fruit Annual Summary, 1955

of processing conflicts with orange concentrate production is another

possible reason for poor quality and resultant poor demand. If it

were possible to require both the processor and fresh fruit packers

to utilize fruit of the highest grade and quality for their particular

purpose and divert their cull fruit into a by-product outlet this condi-

tion could be improved. Assuming that this is possible, the following

information is given to show how whole cull fruit might be disposed

of in a by-product operation.

Primary By-Products of Grapefruit

Since the 1920-30 decade, the processing of citrus fruits has

grown rapidly to become an important part of the Florida Citrus

economy. The industry has grown to such proportions in recent years,

particularly since the development of frozen citrus juice concentrate

in 1945 that more than half the Florida crop is now processed, as shown

in Table 4. The data on oranges is included in Table 4 to show the

great increase in oranges processed and the attendant decrease in

grapefruit processing. Since about half of the fruit is peel, pulp

and seed, a new industry was born out of the necessity to solve a most

difficult waste disposal problem. Today, the processing of by-products

is an essential part of the citrus industry and is also important to

other industries. Dried citrus pulp, molasses and citrus peel oil

are the three primary by-products.

Citrus Pulp and Molasses Dried citrus pulp and citrus molasses are

discussed together at this point since the processing procedure in the

early stages is identical and manufacture of both products can be

accomplished in a balanced operation. Approximately, two and one-half


million tons of dried pulp have been produced in Florida since its
value as a feed was first shown. Many investigators have shown it to

be an excellent bulky carbohydrate feed for both beef and dairy
cattle, with dried grapefruit peel having the further advantage of
containing factors which stimulate milk production in dairy cows.
When citrus molasses was first produced, there was an expansive
growth in the production of this product. It was proved to be an ex-
cellent carbohydrate concentrate, which not only is a feed in itself
but also is used to ensile non-saccharin grasses, to pelletize dried
citrus pulp and to increase the carbohydrate content of dried citrus
pulp and mixed feeds. Citrus molasses has been fortified with urea
to contain an equivalent of 10 to 15 percent crude protein and made
available for stock feeding. In more recent years a greater quantity
of juice has been extracted from the fruit. This is borne out by the
fact that it now requires 5 to 6 tons of wet pulp to produce one ton
of dried pulp; whereas, it used to require 8 to 10 tons of wet pulp
to produce one ton of dried pulp. This means that we are now getting
a dried peel which results in the production of a smaller quantity of
molasses per ton of raw peel. Also, citrus molasses has been com-
petitive with blackstrap molasses which has resulted in a much lower
price for this commodity. Since the price of dried citrus pulp has
remained fairly high it has been advantageous to add back as much
molasses as possible to the dried pulp in order to market citrus
molasses at a more favorable price. Due to these two factors the
quantity of citrus molasses produced in the State has declined. For
purposes of comparison, the quantity of dried citrus pulp and molasses
obtained from one million boxes of Duncan grapefruit is given in
Figure 1. The same information for one million boxes of Marsh

Table 4. Utilization of Orange and Grapefruit Produced
in Florida

Season Oranges Processed Grapefruit Processed
(1) 1,000 Boxes ,Percent 1,000 Boxes Percent
1945-46 19,220 39 22,136 69

1946-47 19,886 37 15,866 55

1947-48 30,421 52 19,451 59

1948-49 26,852 46 16,306 54

1949-50 34,707 59 13,489 55

1950-51 41,915 62 17,853 53

1951-52 47,507 60 13,678 38
1952-53 45,901 64 15,035 46

1953-54 62,904 69 20,089 48

1954-55 60,693 69 15,644 45

(1) Florida Citrus Fruit Annual Summary, 1955


grapefruit is shown in Figure 2. These two varieties of fruit have

been recorded separately since the quantity of product obtained from
each is considerably different. The information given in Figures 1
and 2 is summarized in Table 5.
It can be seen from these data that more molasses and pulp are

produced from Duncan grapefruit than from Marsh grapefruit. This
difference is due to the internal qualities of these two fruits.
However, the quantity of pulp produced is the same, regardless of
the fact that it may be produced from whole fruit or peel only. The

pulp produced in each case is based on an 80 percent add back of the
molasses normally produced from peel only. The increased quantity of
molasses on a whole fruit basis is due to the juice of the fruit
being processed into molasses. If peel only is processed, less

molasses will be made from Duncan fruit than from Marsh fruit. This

is due to the fact that a greater quantity of pulp is produced from
Duncan than from Marsh which in turn utilizes a larger quantity of
the molasses produced from these two sources of peel. On the basis
of one million boxes of whole fruit 2880 tons more molasses would be
produced from Duncan fruit (2315 tons from Marsh seedless) than from
peel only.
At this point it is interesting to take a look at the production
figures for citrus pulp and molasses for the past five years, as

shown in Table 6.
From one million boxes of grapefruit an additional 2000 to 3000
tons of molasses will be produced which will increase the quantity of
this product on the market by 5 to 10 percent. Five million boxes
would produce 20 to 25 percent more molasses than normally produced.

It is not known what effect this quantity of additional molasses would
have on the price and market conditions of this particular product.

Table 5. -

Production of feed and molasses per million
boxes of grapefruit. Whole fruit VS. Peel only.

(1) Tons of Product

Whole Fruit Peel Only
Pulp (1) Molasses (1) Pulp (1) Molasses (1)

Marsh 3,230 2,710 3,230 395

Duncan 4,690 3,040 4,690 160

Fi-ure 1.- Production of Feed ;' > .or ;.:

I.illion Boxes of Duncan lrz: ',ofir ..

25,800,000 Ibs. Press Cake
72.) H20.
7,140,000 lbs. dry Solids

38',000,000 lbs. Ju.cec 10.5 ;:r:,
4,000,000 Ibn. jr:' solids

16,200 00,000::..
1, :,0,000 lbs.

drri sorii.s~

80O Press Ju.ce Add-back

9,3c0,000 lbs. Feed
,6 ons Feed
4,690 lons Feed

6,070,000 :,s. I ::.cs
720 -r:*-"
3 !: rC' I : .. : os

I -
Squiv. to: 5,560,000 Irs.
li:olasses or 2,?0 Tons.
I--- ---------

72O0 r.; I
f' ..

I------- -`

Figure 2.- Production of'Feed & Nolasses for One

Million boxes of Marsh Grapefruit.

uice Add-back I

5,4206000 ibs. Lolasses
72 Brix
2,710 Tor.s classes

iEquiv. to: 4,630,000 lbs. 720 Dri
1iolasses or 2,315 Tons.

37,900,0001bs. Juice 8.80
3,330,000 Ibs. Dry Solids

29,000,000 Ibs. Press Liquor
9.~o Brix
2,840,000 lbs. Dry Solids


The handling of whole grapefruit presents problems which would

require additional research to determine the best method for process-

ing into citrus molasses and pulp. It seems logical that the juice

be extracted from the fruit prior to processing; otherwise, the pulp

in the pug mill would be too fluid to handle in the normal feed mill

operation. Also, lime additions would be excessive, and scale

problems would probably be magnified. Another factor in favor of

juicing prior to processing, is recovery of the essential oil. These

two operations could be carried out simultaneously. It is not known

if molasses produced from juice would be of the same quality as that

produced from the peel. Also, it would be necessary to determine if

lime additions should be made to the juice prior to concentrating;

as well as, determining what effect lime additions would have on the

overall efficiency and operation of the plant from a scale standpoint.

These and many more problems will arise that will require additional


Assuming 135 operating days per year, it is estimated that a

minimum investment of $500,000. would be necessary to process one

million boxes of whole grapefruit into feed and molasses. The equip-

ment necessary for molasses manufacture would be greater than that

necessary for handling peel only. The cost for manufacturing pulp

and molasses is estimated to be as follows:
Dried Citrus Pulp

Fuel Oil: 40 gal/ton @ 60 per gallon $2.40/ton of dry pulp
Labor: 5 men @ $1.00, which includes labor
for sacking and loading cars, based
on l1 tons/hr. 3.33/ton of dry pulp
Power: based on 20/KWH 1.40/ton of dry pulp
Chemicals 0.50/ton of dry pulp
Lubrication oils, etc. 0.50/ton of dry pulp
Cost of new bags 7.20/ton of dry pulp
Fla. Tax Stamps 0.25/ton of dry pulp

TOTAL FEED COST IN BAGS $15.58/ton of dry pulp

Table 6. Total production of citrus pulp and molasses for the
Season 1950-51 through 1954-55 (1)

(1) Citrus Processors Association State of Florida
Production Report.

(2) Tons of Product

Season Pulp and Meal (2) Molasses (2)

1950-51 187,543 70,356

1951-52 218,065 54,035

1952-53 223,311 39,112

1953-54 287,832 52,690
1954-55 262,474 48,934

Citrus Molasses

Fuel Oil: 1 gal. @ 60 per gallon $0.03/gal. of molasses
Power: based on 21/KWH 0.01/gal. of molasses
Labor: 1 man @ $1.25/hr. 0.01/gal. of molasses
Grease oil & incidentals: 0.01/gal. of molasses
TOTAL DIRECT COST $0.06/gal. of molasses

1 Ton of Molasses = 178 gals/ x 60/gal.= $10.68/ton of molasses

Cost data for citrus molasses and pulp are based on direct cost
and do not include cost for fruit or pulp. Also, these costs do not
include amortization annually, insurance and taxes, general overhead
supervision, sales, interest on principal, etc. The possibility on
an investment of $500,000 for processing one million boxes of whole
Marsh grapefruit is as follows:

3,230 tons of pulp @ $35/ton $113,050.00
2,710 tons of Molasses @ $19/ton 51,490.00
Amortization annually $50,000.00
Insurance & Taxes 10,000.00
General overhead supervision,
sales, etc. 15,000.00
Production cost:
Pulp-3230 tons @$15.58
Molasses 2710 tons
@ $10.68 28,942.80
NET RETURN $154.266.20
$ 10,273.80
The possibility on an investment of $500,000 for processing one
million boxes of whole Duncan grapefruit is as follows:


4690 tons of pulp $35/ton $164,150.00
3040 tons of Molasses @ $19/ton 57,760.00

Amortization annually $50,000.00
Insurance & Taxes 10,000.00
General overhead supervision,
sale, etc. 15,000.00
Production cost:
Pulp-4690 tons @$15.58 73,070.00
IMolasses-2710 tons
10.l. 68 28,942.80

NET RETURN 7 44,-97.20

It can be seen from this cost analysis that a net return of

approximately 10 per box could be made on whole Marsh grapefruit by

processing into feed and molasses. For whole Duncan grapefruit, a

net return of about 4.50 per box could be made. Once the plant was

paid for an additional return of 50 per box could be realized. Also,

if this plant were to be operated on two ten hour shifts and two

million boxes of fruit processed an even greater profit could be

realized. However, these figures have been presented on the basis

of one million boxes of fruit for comparison purposes.

Thus it becomes apparent that considerable more research is

necessary to develop other by-products to the point where they can be

made to pay for the cost of production, picking and hauling. Surplus

fruit could then be removed from the market at no cost to the grower

and a good return obtained for that portion of his crop marketed in

normal channels. However, it is quite possible that surplus fruit

could be removed from the market into a by-product operation at a

loss and this loss offset by the increased price obtained for the

fruit marketed. This method leaves much to be desired as the most

suitable means for disposing of surplus fruit. Through an increased


research program it is possible to develop new products of such

value as to make a by-product operation a sound method of disposal.

It has been done in other industries and there is no good reason why

it can't be done in the citrus industry.

Several potential by-products, that could be produced com-

mercially, will be discussed briefly to show how they could increase

the overall value of a whole fruit disposal operation.

Naringin The bitter glucoside, naringin, found only in grape-

fruit offers an excellent possibility for development into a

profitable by-product. Several million pounds occur in the annual

Florida harvest of grapefruit but almost none is recovered for use.

The chemical industry has indicated that a potential market exists

for large tonnages of this glucoside and may bring a price that would

make it a profitable by-product. For the past four years the

Experiment Station has been doing research work to show the quantity

of naringin in Florida grapefruit and how the recovery of this chemical

can tie in with the present practices of handling and processing

fruit. This information is available to the industry in the form of

bulletins and various publications.

The recovery of naringin from Duncan grapefruit was surveyed
for one season, and it was found that from 1 to 13 lbs. of this pro-

duct could be isolated per ton of wet peel. The average recovery was

approximately 6 lbs. per ton of peel. It is estimated that the cost

for producing 1 lb. of this chemical would be no more than $1 per

pound. The process for recovery of this chemical could easily be

integrated in a pulp and molasses plant operation at an additional

cost of about $50,000. In addition to the extraction of this

chemical the pulp would be suitable for the manufacture of cattle

feed and molasses. At the present time naringin is being offered to

the pharmaceutical industry, in quantity lots, for a price of
approximately $7 per pound. It would require about 50 boxes of
whole fruit to give one ton of wet peel or 6 lbs. of naringin. Based

on $7 per pound, the following cost analysis is made for one million
boxes of whole fruit.
120,000 lbs. @ $7/lb. 0 o000.00

Amortization annually $5,000.00
Insurance & Taxes 1,000.00
General overhead super-
vision, Sales, etc. 10,000.00
Production cost:
120,000 lbs. @$l/1b/ 120 000.00
o1ooT 0ooCT 136,000.00
NET PROFIT $704,000.00
It can be seen from this data that a net profit of approximately
700 per box could be made by manufacturing and promoting the use of
this product, providing the price holds up. Only one such product
is necessary to put a whole fruit disposal operation on a sound
economical basis.

Since naringin yields naringenin, glucose and rhamnose upon
hydrolysis, it could be used as a source material for the preparation
of rhamnose. The bitter taste imparted by naringin could be used to
advantage in the preparation of beverage drinks and tonics. Narin-
genin, the product obtained by acid hydrolysis, may be further
hydrolyzed by potassium hydroxide to yield p-coumaric acid and
phloroglucin. These compounds may in turn be used to prepare anti-
oxidants and other synthetic organic chemicals. U. S. Patent No.

2,748,107 Glucoside Azo Dyestuffs has recently been issued to the
University of Florida as a result of our work at the Experiment


Station. Recently, considerable interest has been shown in Vitamin
P like compounds. While they are generally thought to be a mixture

of hesperidin and eriodictin, little is known of their physiological
role in animal metabolism. Other flavanones have been found to be
effective for similar therapeutic uses and in some cases naringin,
or naringenin, has shown greater physiological activity than

hesperidin. It seems quite possible, therefore that the chemical

similarity between naringin and components of Vitamin P will be used
to better advantage, especially so in light of its better solubility.
Grapefruit Beverage Base- The consumption of non-alcoholic bottled
beverages in this country has created a multi-million dollar industry.
In recent years beverages containing fruit juices have contributed
to this volume. However, of the fruit juice beverages that have been
introduced, only citrus beverages, orange, lemon, lime and grapefruit

became widely popular. The production of grapefruit beverage base

might be a more profitable way of utilizing the juice than the
production of citrus molasses.

Grapefruit, Wines, Brandies, Liquors & Vinegar- Like every other fruit
juice containing sugar, citrus juices can be fermented into alcoholic
beverages. Citrus wines do not necessarily possess the characteris-
tics of the fruits from which they are prepared, in the same way that
wines proper do not resemble the flavor of grapes from which they are
fermented. By adding more sugar to the fermenting citrus juices the
alcohol content of the resulting product will also increase. If this
wine is distilled a good brandy can be obtained. Liquors can be pre-

pared from citrus wines by adding sugar and flavoring extracts.
Vinegar in reality is a sour wine. It is made by acetic fermentation
into the final product. Vinegar made from citrus is a very excellent

and much-flavored product. These are interesting possibilities for
the profitable utilization of whole grapefruit.

Grapefruit seed oil- The production of citrus seed oil seems to Y"
highly desirable, since it provides a more profitable outlet for the
seeds than does the processing into dried citrus pulp. Obviously,
only the seedy varieties are suitable. The average yield of wet
seeds from seedy varieties of grapefruit amount to about 5 percent

(4 lbs. per box) based on weight of the whole fruit. The potential
yield of wet seeds from 1 million boxes would then be about 2,000 tons.
From this quantity of seeds a calculated yield of 300 tons of oil
could be produced. Calculated yields are premised on the basis that
wet seeds contain 50 percent moisture and dried seeds contain 30 per-
cent oil. Grapefruit seed oil would be competitive with cotton seed
and peanut oil since they are similar.
2,000 tons of wet seeds dried to an equivalent feed basis of 8%
would give 1090 tons of dried seeds. Since cotton seed oil is selling
for $220/ton a cost analysis will be made on this basis:
Seed oil basis

790 tons as Press Cake @ 035/ton (sold as dried pulp) $26,650.00
300 tons of seed oil @ s220/ton 66.000.00
Feed basis for whole dried seed
1090 tons dried seeds @ $35/ton 38,150.00
If the seeds were separated from one million boxes of seedy
grapefruit, the oil extracted and sold as such an increased return of

$54,500 could be obtained over and above that if processed into pulp.
This would probably add an additional 5.50 profit per box of fruit.

The flavor of grapefruit seed oil resembles that of olive oil, is
pale yellow in color and is considered wholesome and well suited for
food. It can be used after hydrogenation in the manufacture of butter
substitutes and, in some instances, in the production of a cooking fat.
The lower grade oil could be used in the manufacture of soap and in the


preparation of sulfonated oils for the textile industry. A brominated
oil of high density could be produced for the beverage industry. The
seed meal could be broken up and blended with dried pulp and sold as
cattle feed. The hulls could be sold to fertilizer plants as a con-
ditioner for fertilizer.
Fermentation Products- The waste waters from a citrus processing
plant contain one of the cheapest known sources of sugar. It seems
likely that these sugars could be utilized by fermentation to produce
various chemicals such as: antibiotics, lactic acid, yeast and

various other products. To date, very little has been done to explore
the potentialities of these waste by fermentation processes. While
the various possibilities for the utilization of these sugars is un-
known they seem to offer a most interesting line of research for the
profitable disposal of citrus wastes.

Grapefruit oils- In years past there has been a very good demand for
coldpressed grapefruit oil. This oil has been used by the Essential
oil industry primarily as a base material for the manufacture of
synthetic bergamot oil which finds wide use in the perfume industry.
However, during recent years the essential oil industry has started

using molasses plant stripper oil for this purpose. Consequently
during more recent years the demand for Florida coldpressed grapefruit
oil has decreased to such a point that only 10-12,000 lbs. of this oil
is marketed yearly. Plant practice has shown yields of 1.0 to 1.2 lbs.
of this oil per ton of peel. It is estimated that it would require
$60,000 worth of machinery to process the oil at a production cost
of 250 per pound. The 10-12,000 pounds of coldpressed grapefruit oil
sold annually in Florida brings a price of $1.65 per pound; whereas,
it used to bring a price of $2.50 per pound. It is expected that
20,000 lbs. of oil could be produced from one million boxes of grape-


fruit. If this quantity of oil were placed on the market in addition
to that normally produced, this commodity would probably drop below''
that of orange oil which at the present time is selling for 40 per
pound. One interesting fact about coldpressed grapefruit oil is
that it must be aged in cold storage for one year before it is mar-
keted to obtain the best quality oil. The oil produced initially his
a faint by-odor of orange which it looses during storage. This stor-
age would add an additional cost to the oil.
Grapefruit stripper oil could be obtained as a by-product from
the manufacture of citrus molasses. Citrus press liquor contains
0.20 to 0.50 percent oil, and since this oil steam distills readily,
60 to 80 percent of the oil in the liquor can be recovered by flashing
from 2500 F to atmospheric conditions. This oil possess a fine citrus

oil character, marred only by a slight distilled character, and con-
tains very little of the waxy material ordinarily present in expressed
citrus oil. This oil has grown in favor with many chemical firms and
today is selling for 12-180 per pound; whereas, it once sold for 5-64

per pound. It would be well worth while to recover as much of this
product as possible. The recovery of stripper oil could be set up in
conjunction with a molasses plant for an additional equipment cost of
$10-12,000. It is approximated that 50,000 pounds of this oil could
be obtained from one million boxes of whole grapefruit. It is the
accepted plant practice to figure no cost of manufacture for this
product since there are no steam costs and the molasses plant labor
can handle both operations.

Cost analysis on this basis is as follows:

50,000 lbs. @ 150/lb. $75000.
Amortization annually $1200.00 1200.00
$1200.00 $6300.00


This shows that an extra .60 per box can be made by recovering
this oil. Once the original investment is paid for a net profit of

3/40 per box can be realized. While the picture for realizing a pro-
fit on the production of grapefruit oil is rather dim it does point
up the fact that additional research is necessary to up grade the

value of this commodity. Since stripper oil is approximately 95
percent d-limonene it can readily be recognized as an excellent high

purity, low cost source material for making fine organic chemicals.
A synthetic spearmint oil flavor, 1-Carvone, can be manufactured from

this oil. The paint and varnish industry buy considerable quantities

for antiskinning agents. Other uses for this oil are as an ingredient

of clear plastics, as a base for soap perfumes and as a penetrating
Other Potential By-Products- While the foregoing examples are some

of the most striking possibilities of what can be done in a by-

product operation there are many other interesting possibilities that
should not be overlooked. Other products not manufactured now but
with possibilities worthy of development are: menthane fermentation,

ascorbic acid, citric acid, citrus pectin, citrus bland syrup and




The entire discussion up to this point has been concerned with

the by-product disposal of cull grapefruit. There is, however,
another interesting possibility for the disposal of surplus grape-
fruit that offers great promise, but would require further investiga-
tions to exploit its possibilities. In this program the growers would
decide before the picking season began in each year, how many million
boxes of whole grapefruit should be disposed of in a by-product
program. Having decided this, the surplus grapefruit would be picked
prior to September of any season with the actual picking date being
determined by the size returning the most profit in by-products to
the grower.
It is realized that a program of this sort brings with it many
problems, many of which the growers will be required to solve them-
selves, but preliminary evidence shows so many advantages to such a
program that it can not be lightly regarded. Some of the difficult
questions that will need to be answered by the growers are: (1) how
much fruit to dispose of?, (2) where to pick this fruit?, (3) how much
compensation to the grower for his small fruit?, (4) should the tree
or grove be picked clean?, (5) how much will it cost to pick the
smaller sizes?, etc. In the laboratory it will be necessary to deter-
mine the best picking date for optimum by-product return, the yield
or quantity, ease of recovery and how the physical and chemical
characteristics are effected by picking date. All these questions can
be answered by some serious thought, endeavor and research.
Citrus pulp and molasses- Fundamental to the earlier mentioned cull
fruit program is the production of feed and molasses. These products

have their place, but it must be remembered that feed and molasses

Table 7. Monthly Variation in Maturity Data for Duncan Grapefruit.
(Average Values for 1951-52 Season)

Whole Fruit Juices
Date Dia. Inches Weight-grms Dry Solids -

5-1-51 1.2 14 29.9
6-1-51 2.3 76 21.2

7-1-51 3.3 184 17.3
8-1-51 3.7 306 15.6 --

9-1-51 3.8 377 15.2 28.0
10-1-51 4.2 500 15.2 29.0
11-1-51 4.5 577 15.9 38.2
12-1-51 4.6 619 16.5 4.6
1-1-52 4.7 670 16.1 38.9
2-1-52 4.8 742 16.3 40.5

Table 8. Monthly Variation in Maturity Data for Marsh Grapefruit.
(Averages Values for 1951-52 Season).

Date Whole Fruit .
11a.-Inches _cight-.rms. Dry Solids o Juice

5-1-51 .95 9.0 204
6-1-51 2.0 -44 24.4

7-1-51 2.6 111 18.0
8-1-51 2.9 178 15.5 --

9-1-51 3.6 295 13.7 29.5
10-1-51 3.7 339 12.7 40.9

11-1-51 3.9 419 13.0 46.0
12-1-51 4.1 466 12.8 44.4

1-1-52 4.3 550 12.2 44.3
2-1-52 4.5 584 12.6 50.6

yield a gross return of only two and one cents respectively per po.ud

of final fruit product. With small fruit there is every indication
that it will be easier to recover more expensive chemicals worth from

one to seven dollars a pound. But, even if this small fruit were used
to produce feed and molasses the problem would be simpler. From
Tables 7 and 8, which show the monthly variation in maturity data
for Marsh and Duncan Grapefruit, it can be seen that the percent juice
in grapefruit is quite low prior to September. With less juice to con-

tend with, the production of molasses, which has a record of being a
poor money-maker, is reduced. The production of feed is simplified
by the greater percent of dry solids in the fruit which can be ob-

served in the same two tables, 7 and 8. With higher solids there is

less water to be driven off, thereby improving the efficiency of the
operation. There is only one disadvantage a grapefruit weighs only
one-half as much prior to September as it would in February. If the
fruit were picked at an average diameter of three inches, which would

seem to be a good picking size, the fruit would weigh roughly one-
third as much as in February. With earlier picking dates there is

always the increased solids content to improve the yield of feed and
efficiency of operation. The feed and molasses produced from small
fruit is expected to be somewhat different than that produced from
mature peels, but is difficult at this point to say whether the pro-

ducts would be better or worse without further study.
Naringin- Since the glucosides of citrus have become so important
recently the recovery of naringin from small grapefruit is noteworthy.
In Table 9, where the monthly variation in naringin and seed content
of whole Marsh and Duncan grapefruit is shown, it will be noticed that
small fruit contains as much as 10 percent glucoside. As a matter of
fact, Duncan grapefruit, one-half inch diameter, was found to have 80


percent naringin on a dry weight basis as shown in Fig. 3. The sau.c

table shows that in the very small fruit there is a smaller quantity
of naringin by weight due to the smaller weight of the fruit. How-

ever, by August, the weight of naringin in a grapefruit has approached
its maximum. If the fruit were processed in August, twice the quan-

tity of naringin would be obtained. Having a more concentrated source
of naringin greatly simplifies the extraction as well as making it
more efficient. In a recent study, better yields of naringin were ob-
tained from early season fruit as shown in Fig. 4. In this study Dun-
can peel was used and considerable difficulty was encountered in
isolating naringin from fully mature and overmature grapefruit peel.
Yields of naringin per ton of peel extracted was found to be over
twice as great in September as in March. There is every indication
that good yields of naringin can be expected from whole grapefruit
when processed in August. The recovery of naringin is an important
consideration since it is presently selling for seven dollars per

Grapefruit seed oil- Shown also in Table 9., is the percent of seeds

in Duncan and Marsh grapefruit. The quantity of seeds in Marsh grape-
fruit is commercially unimportant, but the noticeably higher percent
by weight of seeds in early Duncan grapefruit could be very important.

Since the seeds from immature Duncan grapefruit account for more than
eight percent of the weight of the fruit, the production of seed oil
may be more profitable and at the same time give an oil more valuable

than that produced from mature fruit.

Pectin- Although pectin is usually produced today from California
lemons there was a time during World War II that considerable pectin

was manufactured from grapefruit peel. The better yield from lemons

has made it a more economical source of pectin. There is every indica-


tion, however, that small grapefruit would be even g1rt~r ..c. ..c
pectin. Although, there is a scarcity of fundamental data, informa-
tion published on early harvested oranges show a minimum of water

soluble pectin and a maximum of protopectin. The yield of acid ex-
tracted pectin recovered from oranges was greatest early in the
season and progressively lower as the fruit matured. It is felt that
this same correlation will hold for grapefruit. The grade of pectin
is likewise very important characteristic, and again the highest
grades of pectin are usually extracted from the more immature fruit.
There is the further possibility that the extraction of pectin and
naringin from the same fruit will decrease the overall production cost
of each item.
Grapefruit oil- During recent years the demand of Florida coldpressed
grapefruit oil has decreased. Large essential oil houses have com-

plained that they have been unable to obtain grapefruit oil which
would meet the flavor requirements as based on oils obtained in the
Since flavor is such an important criterion of quality in citrus
oils, there is considerable chance that oil from immature small grape-
fruit will have a distinctive quality that would be of value to the
essential oil trade. Although there is nothing published in the
literature concerning oil of this type, conditions are favorable for
producing a high quality oil. It must be remembered that internal'
quality of grapefruit has little bearing on the characteristics of
grapefruit oil. Like most essential oils the quality and flavor is
dependent on the quantity of aldehydes present. The aldehydes in
Valencia orange oils continually decrease as the season progresses
which forces the producers of high quality oil to blend their oil over
a part of the season. If the same condition holds for grapefruit, the

Table 9. Monthly Variation in Naringin and Seed Content
of Whole Marsh and Duncan Grapefruit. (Aver-
age values for 1951-52 Season)

Marsh Duncan
Date aringin Nari ngi Seed- .aringin [ar ngin Seeds
l aringng. | 5L

























































. r1 __ _ ii __ _ _ ____ U_ _









20o 0 Whole Fruit
Dry Weight

10 :






1951-52 SEASON

-] Isolated

In Filtrate

R Recycled Filtrate

Oct Nov. Dec. Jon.








Feb. Mar.


highest aldehyde oil will be produced from the most immature fruit.
Grapefruit oil produced from immature or small fruit might bring a
premium price in that it might have a distinctive quality or could
be used for blending to improve the overall quality of the usual type
grapefruit oil.
Other potential benefits of a small fruit program- The production of
by-products from very small immature grapefruit seems to offer poss-
ible unexpected benefits of a monetary nature; as well as, from a
cultural standpoint. In such a program the fruit would be harvested
when it obtained an equatorial diameter of one to two inches and such
diameter would normally occur in April or May. In such a program
possible increased production of fruit would make for a more profit-
able by-product operation. Less equipment and smaller capital invest-
ment would be required to process the fruit.
Cultural benefits of a small fruit program- The overall picture for
the production of by-products from small or immature grapefruit there-
fore shows great promise as there possibly exists even other
possibilities. Besides the monetary return expected from processing
small grapefruit there are other benefits that will accrue. External
quality of the fruit will be of little or no importance in fruit de-
signated for this purpose so savings can be made in the usual spray
and cultural program. Depending on what size of fruit is picked it
is quite possible that a second bloom can be encouraged. Since the
second bloom will probably be of uniform character it could be used
to extend the marketing season for fresh grapefruit. On the other
hand it is understood that if a second bloom is not obtained that
there is the possibility that the bloom will be set somewhat earlier
the next year which would also extend the marketing season for fresh



In this prospectus for the disposal of surplus grapefruit, it

has been shown that two alternatives are possible for the grower.

Either cull and surplus mature grapefruit or immature and very small

fruit can be processed into the various products described. Al-

though such a program is rather radical when compared to present day

practice, it shows great promise. Further research will possibly

bear out the unthought potentialities of such a program. All of this

leads to the inevitable conclusion that grapefruit possess a wealth

of raw materials that should be considered a most valuable asset to

the grower.

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