• TABLE OF CONTENTS
HIDE
 Front Cover
 Title Page
 Table of Contents
 Introduction
 Literature review
 Chemical composition and const...
 Methods
 Nutritional aspects
 Utilization
 Literature cited
 Back Cover






Group Title: Agricultural Experiment Station Bulletin 756
Title: Citrus seed oils
CITATION PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027159/00001
 Material Information
Title: Citrus seed oils
Physical Description: 30 p. : ill. ; 23 cm.
Language: English
Creator: Braddock, R. J ( Robert James )
Kesterson, J. W
University of Florida -- Agricultural Experiment Station
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1973
 Subjects
Subject: Citrus oils   ( lcsh )
Citrus fruits -- By-products -- Florida   ( lcsh )
Citrus fruits -- Research -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by R.J. Braddock and J.W. Kesterson.
Bibliography: Bibliography: p.27-30.
Funding: Bulletin - Florida Agricultural Experiment Station Bulletin ; 756
 Record Information
Bibliographic ID: UF00027159
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: aleph - 000929625
oclc - 16310770
notis - AEP0418

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Table of Contents
        Table of Contents
    Introduction
        Page 1
    Literature review
        Page 1
    Chemical composition and constants
        Page 2
        Fatty acids
            Page 2
        Glycerides
            Page 3
            Page 4
        Phospholipids
            Page 5
        Other compounds
            Page 5
        Constants
            Page 5
            Page 6
            Page 7
    Methods
        Page 8
        Analytical
            Page 8
            Specific gravity
                Page 8
            Refractive index
                Page 8
            Acid value
                Page 8
            Iodine value
                Page 9
            Saponification number
                Page 9
            Acetyl value
                Page 9
            Reichert-Meissl number
                Page 9
            Polenske number
                Page 9
                Page 10
            Hehner value
                Page 11
        Processing
            Page 11
            Page 12
            Dehulling
                Page 13
            Reduction
                Page 13
            Cooking
                Page 13
            Oil expression and extraction
                Page 14
            Refining
                Page 14
                Page 15
            Limonin recovery from crude oil
                Page 16
            Degumming
                Page 16
            Bleaching
                Page 16
            Deodorizing
                Page 16
            Winterization
                Page 17
            Hydrogenation
                Page 17
            Interesterification
                Page 17
        Quality control
            Page 17
            Heat treatment
                Page 17
            Color
                Page 18
            Free fatty acids
                Page 18
            Rancidity
                Page 18
            Peroxide determination
                Page 18
            TBA number
                Page 19
            Antioxidants
                Page 19
            Smoke, flash and fire points
                Page 20
    Nutritional aspects
        Page 20
        Seed oil
            Page 20
        Seed meal
            Page 21
            Page 22
            Page 23
    Utilization
        Page 24
        Page 25
        Page 26
    Literature cited
        Page 27
        Page 28
        Page 29
        Page 30
    Back Cover
        Back Cover
Full Text
Bulletin 756 (technical)


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


April 1973


















CITRUS SEED OILS

By

R. J. Braddock and J. W. Kesterson


The authors are with the University of Florida, Institute of Food
and Agricultural Sciences, Agricultural Research and Education
Center, Lake Alfred, Florida 33850.

















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















CONTENTS

Page

INTRODUCTION ...........----.. ...--- ... --- ....--- --.... 1
LITERATURE REVIEW ...........-...... .......... ..... ------- .... 1
CHEMICAL COMPOSITION AND CONSTANTS ....---.........--.----- 2
Fatty Acids .....2........ .............. -- .. -------- 2
Glycerides ..-..-.. .............-------------- 3
Phospholipids -- ------ ...5..-- ----- ....------- -- ------- 5
Other Compounds .....-.............- -----...--- ...-- ---- 5
Constants ..... .. ...... ................................. 5
METHODS ...---......~.------------.. .... -----..--- 8
Analytical .......... ...... ................................-- 8
Specific Gravity --...... ............. ......... ..........--- 8
Refractive Index -.......... ........ .. .................... 8
Acid Value 9.......... .............-------...----- 9
Iodine Value ...........--- ...... ... .................----- 8
Saponification Number ..............- ... ..---....-...-.. --...--- 9
Acetyl Value .........--......................... ----- 9
Reichert-Meissl Number ...............-- ---.............. 9
Polenske Number .--...............--- .----------- -....... 9
Hehner Value .....--.. ... .... .--------............ -... 11
Processing .................................................. 11
Dehulling .......................... ................... 13
Reduction .. ............... ............................ 13
Cooking ................- ....-.. .---------........ .-- 13
Oil Expression and Extraction ............. .. ..........----. -- 14
Refining .............--... ................... ....-----.. .- 14
Limonin Recovery from Crude Oil .....................--....- .. 16
Degumming .. ....... .... ........................... ... 16
Bleaching ...---........-------------- 16
Deodorizing -..-.......--.......... .-- ...16
W interization -... ...... ............. ..-......--- ------- 17
Hydrogenation ................ .............. ..------- 17
Interesterification .............--............. ..-------- 17
Quality Control .. ................ ... .................. ... 17
Heat Treatment ......-........... -- ...........17
Color ............. .................................... 18
Free Fatty Acids ...............---- ... ..........------- 18
Rancidity ......._- .. .... ..... ..........-----------.. 18
Peroxide Determination .............--- ..-----------......... 18
TBA Number ..... ....-.........---- ---- ... ..- -- -19
Antioxidants ....-.. ............--------..... .------- 19
Pro-oxidants ....... -------------............ 20
Smoke, Flash and Fire Points ..-- ~~..~.....---------. ---------- --- 20
NUTRITIONAL ASPECTS .................. ............. .. 20
Seed Oil ......-- --- ... ...----- .-............ 20
Seed Meal .......-......-...- ......-- ..-- ......- .. --. ..- 21
UTILIZATION .................... .......................------- 24
LITERATURE CITED .-..............- .........---------- 27








Citrus Seed Oils


INTRODUCTION
Increased production and processing of many different com-
mercially valuable specialty products from citrus fruits has
become a reality in the last decade. Continuation of this trend
into the immediate future is almost certain, since the potential
value of these products to the citrus industry is now being
realized. The industrial value for many of these by-products
may be great when one considers that money would have to be
spent for pollution or waste control if the products were not
developed into marketable commodities. Recovery of (+)-limo-
nene from plant centrifuge effluents is just one example of such
a product.
It has been an industrial practice to include the seeds from
processed citrus fruit with the peel and pulp portion during the
production of dried cattle feed. However, the amount of seeds
found in the feed is in no way uniform from batch to batch,
since some of the varieties processed have few or no seeds
(Hamlin and Valencia oranges, Marsh grapefruit). Since the
seeds contain valuable oil and protein suitable for human con-
sumption, it would be much more profitable if they were proc-
essed separately for this utilization and not included in feed
for livestock.
At present, no citrus seed oil is produced commercially in
Florida, the last manufacturing operation having ceased pro-
duction during the 1969-70 season. However, there is current
interest within the industry to produce this specialty product
again, and at least one processor is making plans to start pro-
duction of crude oil. In the last 70 years, considerable research
has been published regarding the chemical and physical char-
acteristics of various citrus seed oils. However, no attempt has
been made to summarize the literature and make this informa-
tion generally available, as has been done in the case of other
commercially valuable oil seeds. This bulletin has been prepared
to consolidate the scientific information regarding citrus seeds
and their oils and to assist the citrus industry with utilization
and processing of this valuable commodity.

LITERATURE REVIEW
Citrus seeds have long been recognized as a source of edible
oil with characteristics suitable for human consumption and








Citrus Seed Oils


INTRODUCTION
Increased production and processing of many different com-
mercially valuable specialty products from citrus fruits has
become a reality in the last decade. Continuation of this trend
into the immediate future is almost certain, since the potential
value of these products to the citrus industry is now being
realized. The industrial value for many of these by-products
may be great when one considers that money would have to be
spent for pollution or waste control if the products were not
developed into marketable commodities. Recovery of (+)-limo-
nene from plant centrifuge effluents is just one example of such
a product.
It has been an industrial practice to include the seeds from
processed citrus fruit with the peel and pulp portion during the
production of dried cattle feed. However, the amount of seeds
found in the feed is in no way uniform from batch to batch,
since some of the varieties processed have few or no seeds
(Hamlin and Valencia oranges, Marsh grapefruit). Since the
seeds contain valuable oil and protein suitable for human con-
sumption, it would be much more profitable if they were proc-
essed separately for this utilization and not included in feed
for livestock.
At present, no citrus seed oil is produced commercially in
Florida, the last manufacturing operation having ceased pro-
duction during the 1969-70 season. However, there is current
interest within the industry to produce this specialty product
again, and at least one processor is making plans to start pro-
duction of crude oil. In the last 70 years, considerable research
has been published regarding the chemical and physical char-
acteristics of various citrus seed oils. However, no attempt has
been made to summarize the literature and make this informa-
tion generally available, as has been done in the case of other
commercially valuable oil seeds. This bulletin has been prepared
to consolidate the scientific information regarding citrus seeds
and their oils and to assist the citrus industry with utilization
and processing of this valuable commodity.

LITERATURE REVIEW
Citrus seeds have long been recognized as a source of edible
oil with characteristics suitable for human consumption and








food use. At the turn of the century, German researchers iden-
tified palmitic, stearic, oleic, linoleic, and linolenic acids as con-
stituents of citrus seed glycerides (13).1 The same researchers
also determined many of the physical and chemical character-
istics of the seed oils from sour oranges and lemons (41). The
earliest references described the oil as having an intense bitter
taste due to the presence of limonin (33, 35, 41).
Other early research describes the appearance and proximate
analyses of four varieties of orange and grapefruit seed oils (4)
and some of the oil characteristics such as refractive index,
saponification number, iodine value, and relative viscosity (11).
The protein, fiber, ash, water, and crude fat content of air dried
citrus seeds were reported for three varieties of Japanese
oranges (32). The chemical and physical characteristics of
grapefruit seed oil have been reported by several researchers
(15, 22, 28, 37, 47). Grapefruit seed yields per weight of fruit
have also been studied (19).
Analyses have been performed on orange seeds and seed oils
to determine component fatty acids of the glycerides (12, 18,
20, 24, 39, 45) and other physicochemical characteristics and
processing methods (21, 27, 48, 51, 53). Mandarin orange seed
oils have been separately characterized (10, 26), as have seed
oils from tangerines (46), Ceylon sweet oranges (54), bitter
oranges (38, 56), and several types of Indian citrus, including
shaddock and calamondins (1, 34, 42). Descriptions of lemon
seed oils have been published (17, 25), and lime seed oil has
been described by Oilar as light-colored oil, desirable as a salad
oil (40).
Biological and nutritive properties of citrus seeds have also
been studied. Experiments have been performed to ascertain
the germination and viability of citrus seeds (36) and establish
the microscopic structure of grapefruit, orange, lemon, and lime
seeds (52). The nutritive value of citrus seed protein in defatted
meal has also been determined (3), while the processed oils were
described as non-toxic and as digestible as other common seed
oils, such as soybean and cottonseed oil (7, 43).


CHEMICAL COMPOSITION AND CONSTANTS
Fatty Acids.-The seed oils of all varieties of citrus are com-
posed of significant amounts of polyunsaturated fatty acids, and
in most cases the extracted oil is liquid at room temperature.
'Numbers in parentheses refer to Literature Cited.








food use. At the turn of the century, German researchers iden-
tified palmitic, stearic, oleic, linoleic, and linolenic acids as con-
stituents of citrus seed glycerides (13).1 The same researchers
also determined many of the physical and chemical character-
istics of the seed oils from sour oranges and lemons (41). The
earliest references described the oil as having an intense bitter
taste due to the presence of limonin (33, 35, 41).
Other early research describes the appearance and proximate
analyses of four varieties of orange and grapefruit seed oils (4)
and some of the oil characteristics such as refractive index,
saponification number, iodine value, and relative viscosity (11).
The protein, fiber, ash, water, and crude fat content of air dried
citrus seeds were reported for three varieties of Japanese
oranges (32). The chemical and physical characteristics of
grapefruit seed oil have been reported by several researchers
(15, 22, 28, 37, 47). Grapefruit seed yields per weight of fruit
have also been studied (19).
Analyses have been performed on orange seeds and seed oils
to determine component fatty acids of the glycerides (12, 18,
20, 24, 39, 45) and other physicochemical characteristics and
processing methods (21, 27, 48, 51, 53). Mandarin orange seed
oils have been separately characterized (10, 26), as have seed
oils from tangerines (46), Ceylon sweet oranges (54), bitter
oranges (38, 56), and several types of Indian citrus, including
shaddock and calamondins (1, 34, 42). Descriptions of lemon
seed oils have been published (17, 25), and lime seed oil has
been described by Oilar as light-colored oil, desirable as a salad
oil (40).
Biological and nutritive properties of citrus seeds have also
been studied. Experiments have been performed to ascertain
the germination and viability of citrus seeds (36) and establish
the microscopic structure of grapefruit, orange, lemon, and lime
seeds (52). The nutritive value of citrus seed protein in defatted
meal has also been determined (3), while the processed oils were
described as non-toxic and as digestible as other common seed
oils, such as soybean and cottonseed oil (7, 43).


CHEMICAL COMPOSITION AND CONSTANTS
Fatty Acids.-The seed oils of all varieties of citrus are com-
posed of significant amounts of polyunsaturated fatty acids, and
in most cases the extracted oil is liquid at room temperature.
'Numbers in parentheses refer to Literature Cited.








The major fatty acids of the seed glycerides include palmitic
(16:0)2, palmitoleic (16:1), stearic (18:0), oleic (18:1), linoleic
(18:2), and linolenic (18:3) acids. General ranges for these
fatty acids are listed in Table 1 for oranges, grapefruit, lemon,
lime, and mandarin seed oils. The seed oils from the citrus va-
rieties listed are all similar in fatty acid composition, the most
notable difference being the higher linolenic (18:3) acid content
of the lemons and limes. It has been reported that linolenic acid
from crushed seeds may be one of the causes of flavor deterio-
ration in processed lemon juices, whereas juices of citrus culti-
vars whose seeds contain lesser quantities of this fatty acid may
be more stable (20).
The major fatty acids and the percentages (by wet weight)
of seeds in many individual varieties of Florida citrus are listed
in Table 2. These data are averages of three analyses for each
variety of fruit, picked when mature from groves at Lake Al-
fred. The orange seed oils all have similar compositions, as do
most of the grapefruit. Distinguishing features are the gen-
erally higher palmitic acid (16:0) content of the grapefruit,
lower linolenic acid (18:3) content of oranges, more linoleic
(18:2) acid found in mandarin-types, and greater quantities of
linolenic and lesser amounts of palmitic and oleic acids in lemon
and key lime seed oils. Calamondin, Kumquat, and Meyer lemon
seed oils were found to have much greater quantities of palmi-
toleic acid (16:1) than seed oils of the other varieties. The pres-
ence of linolenic acid in the seed oils of citrus may be a deterrent
if long-term storage stability is required.
Glycerides.-The neutral lipid fraction of the seed oil from
citrus varieties contains primarily triglycerides, as does that
from most oil bearing seeds. Citrus seed oils have been reported
to contain negligible amounts of fully saturated glycerides but
larger quantities of mono-unsaturated glycerides (15). The prop-
erties and characteristics of the crude and refined oil are similar
to cottonseed oil, except that the citrus seed oil may be more
subject to oxidative rancidity because of the presence of lino-
lenic acid in the glycerides. This fatty acid is present only in
traces in cottonseed oil.
Experimental data indicates that citrus seed oils generally
contain about 20% of glycerides with two palmitic acid groups
and 50% of glycerides with one palmitic acid group. The re-
maining groups on the triglycerides are primarily either oleic,

2The notation indicates carbon chain length: number of C = C double
bonds in the chain.

















Table 1. Range of Fatty Acid Composition in Florida Citrus and Other Seed Oils.
Component Acids, %

Seed Type Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic
Oranges (24. 39* 26-31 0.1 3-5 24-28 35-37 2-4


Grapefruit (22, 47)
S Mandarins (26)
Lemons (24, 25, 39)
Limes (15, 25, 39)
Cottonseed (8)
Soybean (8)


26-36
22-30
20-24
24-29
20-23


0.1-0.3
0.1-1.0
0.1-0.3
0.1-0.5


18-25
20-25
26-31
20-22
23-35
15-33


32-40
37-45
31-38
37-40
42-54
43-56


3-6
3-5
8-12
6-11


5-11


*Numbers in parentheses refer to Literature Cited.








linoleic, or linolenic acids (6, 15). Table 3 shows the distribution
of the fatty acids in the three available positions of triglycerides
from commercial citrus seed oil. This data was calculated from
the total fatty acid composition of the seed oil triglycerides and
clearly shows the predominance of palmitic and stearic acids at
the 1-position and linoleic acid at the 2-position.

Phospholipids.-The phospholipid fraction of the seed lipids
consists primarily of phosphatidyl choline (lecithin) and phos-
phatidyl ethanolamine (cephalin). These two phospholipids com-
prise approximately 85% to 90% of the total phospholipids, the
remainder being phosphatidyl inositol (10% to 15%) and phos-
phatidyl serine (1% to 5%). These ranges represent analyses
performed for one season only, but should be considered repre-
sentative of most classes of citrus seeds as no deviations from
these values have been observed in the authors' laboratory.
The phosphatide content (2) of crude citrus seed oils pro-
duced by expelling without solvent extraction was in the range
0.3% to 1.1%. This quantity is sufficiently high to warrant de-
gumming of the crude oil in order to reduce the phosphatide
content of the neutral oil. There is a market for the crude leci-
thin from the degumming process for use in some food and feed
formulations.
Other Compounds.-Grapefruit seed oil has been found to
contain several sterols, which include mostly beta-sitosterol and
lesser amounts of campesterol and stigmasterol (9). Some cou-
marin compounds and limonin also have been reported in the
seeds and seed oils (30).

Constants.-Some of the chemical and .physical properties of
seed oils from various citrus varieties and cultivars have been
summarized in part by Eckey (16) and listed for convenience in
Table 4. These values from the literature may be used for com-
parison purposes and, in some cases, are measures of the quality
of a seed oil. Examination of Table 4 shows that the properties
of almost all the oils from the different citrus fruits are similar.
For example, the iodine values all lie in the range from 85 to 110
with lemon and tangerine seed oils usually having the highest
iodine values. The grapefruit oil (28) listed in the table has an
unusually high iodine value and does not conform to, values ob-
tained in our laboratory. Higher iodine values of lemon and
tangerine seed oils are supported by the authors' research (Table
2) showing greater amounts of linoleic and linolenic acid in these
oils. Variability of the values in Table 4 can be attributed to the








linoleic, or linolenic acids (6, 15). Table 3 shows the distribution
of the fatty acids in the three available positions of triglycerides
from commercial citrus seed oil. This data was calculated from
the total fatty acid composition of the seed oil triglycerides and
clearly shows the predominance of palmitic and stearic acids at
the 1-position and linoleic acid at the 2-position.

Phospholipids.-The phospholipid fraction of the seed lipids
consists primarily of phosphatidyl choline (lecithin) and phos-
phatidyl ethanolamine (cephalin). These two phospholipids com-
prise approximately 85% to 90% of the total phospholipids, the
remainder being phosphatidyl inositol (10% to 15%) and phos-
phatidyl serine (1% to 5%). These ranges represent analyses
performed for one season only, but should be considered repre-
sentative of most classes of citrus seeds as no deviations from
these values have been observed in the authors' laboratory.
The phosphatide content (2) of crude citrus seed oils pro-
duced by expelling without solvent extraction was in the range
0.3% to 1.1%. This quantity is sufficiently high to warrant de-
gumming of the crude oil in order to reduce the phosphatide
content of the neutral oil. There is a market for the crude leci-
thin from the degumming process for use in some food and feed
formulations.
Other Compounds.-Grapefruit seed oil has been found to
contain several sterols, which include mostly beta-sitosterol and
lesser amounts of campesterol and stigmasterol (9). Some cou-
marin compounds and limonin also have been reported in the
seeds and seed oils (30).

Constants.-Some of the chemical and .physical properties of
seed oils from various citrus varieties and cultivars have been
summarized in part by Eckey (16) and listed for convenience in
Table 4. These values from the literature may be used for com-
parison purposes and, in some cases, are measures of the quality
of a seed oil. Examination of Table 4 shows that the properties
of almost all the oils from the different citrus fruits are similar.
For example, the iodine values all lie in the range from 85 to 110
with lemon and tangerine seed oils usually having the highest
iodine values. The grapefruit oil (28) listed in the table has an
unusually high iodine value and does not conform to, values ob-
tained in our laboratory. Higher iodine values of lemon and
tangerine seed oils are supported by the authors' research (Table
2) showing greater amounts of linoleic and linolenic acid in these
oils. Variability of the values in Table 4 can be attributed to the








linoleic, or linolenic acids (6, 15). Table 3 shows the distribution
of the fatty acids in the three available positions of triglycerides
from commercial citrus seed oil. This data was calculated from
the total fatty acid composition of the seed oil triglycerides and
clearly shows the predominance of palmitic and stearic acids at
the 1-position and linoleic acid at the 2-position.

Phospholipids.-The phospholipid fraction of the seed lipids
consists primarily of phosphatidyl choline (lecithin) and phos-
phatidyl ethanolamine (cephalin). These two phospholipids com-
prise approximately 85% to 90% of the total phospholipids, the
remainder being phosphatidyl inositol (10% to 15%) and phos-
phatidyl serine (1% to 5%). These ranges represent analyses
performed for one season only, but should be considered repre-
sentative of most classes of citrus seeds as no deviations from
these values have been observed in the authors' laboratory.
The phosphatide content (2) of crude citrus seed oils pro-
duced by expelling without solvent extraction was in the range
0.3% to 1.1%. This quantity is sufficiently high to warrant de-
gumming of the crude oil in order to reduce the phosphatide
content of the neutral oil. There is a market for the crude leci-
thin from the degumming process for use in some food and feed
formulations.
Other Compounds.-Grapefruit seed oil has been found to
contain several sterols, which include mostly beta-sitosterol and
lesser amounts of campesterol and stigmasterol (9). Some cou-
marin compounds and limonin also have been reported in the
seeds and seed oils (30).

Constants.-Some of the chemical and .physical properties of
seed oils from various citrus varieties and cultivars have been
summarized in part by Eckey (16) and listed for convenience in
Table 4. These values from the literature may be used for com-
parison purposes and, in some cases, are measures of the quality
of a seed oil. Examination of Table 4 shows that the properties
of almost all the oils from the different citrus fruits are similar.
For example, the iodine values all lie in the range from 85 to 110
with lemon and tangerine seed oils usually having the highest
iodine values. The grapefruit oil (28) listed in the table has an
unusually high iodine value and does not conform to, values ob-
tained in our laboratory. Higher iodine values of lemon and
tangerine seed oils are supported by the authors' research (Table
2) showing greater amounts of linoleic and linolenic acid in these
oils. Variability of the values in Table 4 can be attributed to the








Table 2. Fatty Acid Composition of Citrus Seed Oils.
Component Acids, % Percent Wet Seeds
in

Seed Type Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic Whole Fruit
Grapefruit
Duncan 35 0.1 3 21 37 4 7
Excelsior 34 tr 4 22 36 4 4
Foster 30 0.2 4 23 37 5 5
Marsh 35 tr 3 21 36 4 0.2
Ruby Red 35 0.3 4 25 29 6 0.1
Shaddock 28 tr 4 26 37 4 5
Walters 35 tr 4 21 37 4 6
Oranges
Hamlin 32 0.1 4 24 37 3 0.4
Parson Brown 31 0.1 4 25 37 3 2
Pineapple 30 tr 5 25 37 3 3
Sour Orange* 31 2 4 28 29 5 4
Valencia 28 0.1 5 28 36 3 1
Mandarin-Type
Clementine 31 0.7 4 21 40 3 3
Dancy Tangerine 24 0.8 4 23 43 5 1
King 30 tr 4 19 44 3 2
Murcott 31 tr 2 21 41 5 3
Robinson* 26 2.0 6 22 39 5 2
Satsuma 29 0.7 5 22 39 4 0.5
Minneola* 32 3 4 21 34 6 0.7
Orlando 27 0.2 4 22 43 4 0.7
Temple 26 tr 4 27 39 4 2
















Lemons
Avon 25 0.2 3 30 30 12 1
Bearss 24 0.1 4 26 34 12 0.7
Eureka 20 0.1 3 28 38 11 0.5
Lisbon 23 tr 4 30 31 12 1
Meyer* 24 4 4 32 32 4 0.6
Ponderosa 24 0.2 4 49 19 4 -
Rough* 18 4 6 24 42 6 1
S Sicilian 23 tr 4 31 32 10 0.7
Villa Franca 23 tr 4 30 33 10 2
Limes
Key 25 0.3 5 22 37 11 2
Persian 29 0.1 5 22 39 5 0.1
Calamondin* 21 5 6 26 34 8 2
Kumquat* 30 4 5 18 36 7 0.4

"Component fatty acids were determined on purified triglycerides from the seed oil.








Table 3. Calculated Triglyceride Structure of Commercial Citrus Seed Oil.
Glyceride Glyceride Distribution, %
Position
Fatty Acids Total, % 1 2 3
16:0 35 17.3 0.4 17.3
18:0 3 1.5 0.0 1.5
18:1 21 7.0 7.0 7.0
18:2 37 5.8 24.6 5.8
18:3 4 1.3 1.3 1.3

different methods and fruit sources used by the numerous
authors cited. The use and meaning of the various constants
presented in Table 4 will be discussed in the next section under
methods.


METHODS
Analytical
The chemical and physical properties and composition of
commercial seed oils are determined by standard analytical
methods as set forth by the American Oil Chemists' Society (2).
Specific instructions are given regarding sample size, apparatus,
and procedure for analysis of an oil. Considerable information
about chemical reactions, structure, chemical characteristics,
physical properties, and composition of many different fats and
oils is presented in Bailey (8). A brief description of certain
physical and chemical properties of oils useful in processing tech-
nology is given below.
Specific Gravity.-Because of different melting properties of
various fats, specific gravity may be determined at several tem-
peratures. Generally, 25 C is satisfactory for most citrus seed
oils, which are liquid at this temperature. Variations of specific
gravity are usually small for most oils.
Refractive Index.-This property of fats and oils increases
in value with greater unsaturation and/or increasing carbon
chain length of the component fatty acids. Refractive index
may be useful in identification and checking the purity of citrus
seed oils, since values published in Table 4 show no great vari-
ability among cultivars or varieties.
Acid Value.-The free fatty acids present in a neutral fat or
oil are a measure of refining efficiency. Refined oils of good qual-








Table 3. Calculated Triglyceride Structure of Commercial Citrus Seed Oil.
Glyceride Glyceride Distribution, %
Position
Fatty Acids Total, % 1 2 3
16:0 35 17.3 0.4 17.3
18:0 3 1.5 0.0 1.5
18:1 21 7.0 7.0 7.0
18:2 37 5.8 24.6 5.8
18:3 4 1.3 1.3 1.3

different methods and fruit sources used by the numerous
authors cited. The use and meaning of the various constants
presented in Table 4 will be discussed in the next section under
methods.


METHODS
Analytical
The chemical and physical properties and composition of
commercial seed oils are determined by standard analytical
methods as set forth by the American Oil Chemists' Society (2).
Specific instructions are given regarding sample size, apparatus,
and procedure for analysis of an oil. Considerable information
about chemical reactions, structure, chemical characteristics,
physical properties, and composition of many different fats and
oils is presented in Bailey (8). A brief description of certain
physical and chemical properties of oils useful in processing tech-
nology is given below.
Specific Gravity.-Because of different melting properties of
various fats, specific gravity may be determined at several tem-
peratures. Generally, 25 C is satisfactory for most citrus seed
oils, which are liquid at this temperature. Variations of specific
gravity are usually small for most oils.
Refractive Index.-This property of fats and oils increases
in value with greater unsaturation and/or increasing carbon
chain length of the component fatty acids. Refractive index
may be useful in identification and checking the purity of citrus
seed oils, since values published in Table 4 show no great vari-
ability among cultivars or varieties.
Acid Value.-The free fatty acids present in a neutral fat or
oil are a measure of refining efficiency. Refined oils of good qual-








Table 3. Calculated Triglyceride Structure of Commercial Citrus Seed Oil.
Glyceride Glyceride Distribution, %
Position
Fatty Acids Total, % 1 2 3
16:0 35 17.3 0.4 17.3
18:0 3 1.5 0.0 1.5
18:1 21 7.0 7.0 7.0
18:2 37 5.8 24.6 5.8
18:3 4 1.3 1.3 1.3

different methods and fruit sources used by the numerous
authors cited. The use and meaning of the various constants
presented in Table 4 will be discussed in the next section under
methods.


METHODS
Analytical
The chemical and physical properties and composition of
commercial seed oils are determined by standard analytical
methods as set forth by the American Oil Chemists' Society (2).
Specific instructions are given regarding sample size, apparatus,
and procedure for analysis of an oil. Considerable information
about chemical reactions, structure, chemical characteristics,
physical properties, and composition of many different fats and
oils is presented in Bailey (8). A brief description of certain
physical and chemical properties of oils useful in processing tech-
nology is given below.
Specific Gravity.-Because of different melting properties of
various fats, specific gravity may be determined at several tem-
peratures. Generally, 25 C is satisfactory for most citrus seed
oils, which are liquid at this temperature. Variations of specific
gravity are usually small for most oils.
Refractive Index.-This property of fats and oils increases
in value with greater unsaturation and/or increasing carbon
chain length of the component fatty acids. Refractive index
may be useful in identification and checking the purity of citrus
seed oils, since values published in Table 4 show no great vari-
ability among cultivars or varieties.
Acid Value.-The free fatty acids present in a neutral fat or
oil are a measure of refining efficiency. Refined oils of good qual-








Table 3. Calculated Triglyceride Structure of Commercial Citrus Seed Oil.
Glyceride Glyceride Distribution, %
Position
Fatty Acids Total, % 1 2 3
16:0 35 17.3 0.4 17.3
18:0 3 1.5 0.0 1.5
18:1 21 7.0 7.0 7.0
18:2 37 5.8 24.6 5.8
18:3 4 1.3 1.3 1.3

different methods and fruit sources used by the numerous
authors cited. The use and meaning of the various constants
presented in Table 4 will be discussed in the next section under
methods.


METHODS
Analytical
The chemical and physical properties and composition of
commercial seed oils are determined by standard analytical
methods as set forth by the American Oil Chemists' Society (2).
Specific instructions are given regarding sample size, apparatus,
and procedure for analysis of an oil. Considerable information
about chemical reactions, structure, chemical characteristics,
physical properties, and composition of many different fats and
oils is presented in Bailey (8). A brief description of certain
physical and chemical properties of oils useful in processing tech-
nology is given below.
Specific Gravity.-Because of different melting properties of
various fats, specific gravity may be determined at several tem-
peratures. Generally, 25 C is satisfactory for most citrus seed
oils, which are liquid at this temperature. Variations of specific
gravity are usually small for most oils.
Refractive Index.-This property of fats and oils increases
in value with greater unsaturation and/or increasing carbon
chain length of the component fatty acids. Refractive index
may be useful in identification and checking the purity of citrus
seed oils, since values published in Table 4 show no great vari-
ability among cultivars or varieties.
Acid Value.-The free fatty acids present in a neutral fat or
oil are a measure of refining efficiency. Refined oils of good qual-








Table 3. Calculated Triglyceride Structure of Commercial Citrus Seed Oil.
Glyceride Glyceride Distribution, %
Position
Fatty Acids Total, % 1 2 3
16:0 35 17.3 0.4 17.3
18:0 3 1.5 0.0 1.5
18:1 21 7.0 7.0 7.0
18:2 37 5.8 24.6 5.8
18:3 4 1.3 1.3 1.3

different methods and fruit sources used by the numerous
authors cited. The use and meaning of the various constants
presented in Table 4 will be discussed in the next section under
methods.


METHODS
Analytical
The chemical and physical properties and composition of
commercial seed oils are determined by standard analytical
methods as set forth by the American Oil Chemists' Society (2).
Specific instructions are given regarding sample size, apparatus,
and procedure for analysis of an oil. Considerable information
about chemical reactions, structure, chemical characteristics,
physical properties, and composition of many different fats and
oils is presented in Bailey (8). A brief description of certain
physical and chemical properties of oils useful in processing tech-
nology is given below.
Specific Gravity.-Because of different melting properties of
various fats, specific gravity may be determined at several tem-
peratures. Generally, 25 C is satisfactory for most citrus seed
oils, which are liquid at this temperature. Variations of specific
gravity are usually small for most oils.
Refractive Index.-This property of fats and oils increases
in value with greater unsaturation and/or increasing carbon
chain length of the component fatty acids. Refractive index
may be useful in identification and checking the purity of citrus
seed oils, since values published in Table 4 show no great vari-
ability among cultivars or varieties.
Acid Value.-The free fatty acids present in a neutral fat or
oil are a measure of refining efficiency. Refined oils of good qual-








ity should have a very low acid value, while crude oils or oils
which have been abused have greater quantities of free fatty
acids. The presence of significant quantities of free acids in an
oil will result in lowering the smoke point, an undesirable fea-
ture if the oil is to be used for frying purposes.

Iodine Value.-The iodine value is the number of grams of
12 absorbed per 100 gm of fat or oil, based on addition to carbon-
carbon double bonds of the unsaturated fatty acids in the oil.
The iodine value increases with increasing unsaturation of an
oil and decreases with increasing melting point. Iodine value in-
creases linearly with increasing refractive index, and this rela-
tionship has been published for seed oils of the major citrus
cultivars (24).
Saponification Number.-This characteristic of seed oils is
sometimes referred to as the Koettstorfer number, a term now
in disuse. By definition, the saponification number is the milli-
grams of potassium hydroxide necessary to saponify 1 gm of
fat, and is a measure of the average length of the fatty acid
chains attached to the glycerides in a fat. Generally, the sapon-
ification value increases as the average molecular weight of the
triglycerides in a fat decreases. For example, unusually high
values are obtained from fats such as milk fat, coconut, and
palm kernel oils, which have larger amounts of short chain fatty
acids. Values for most citrus seed oils listed in Table 4 lie in
the range of 185 to 200, although one report (12) gives an ab-
normally high value for Bitter orange.
Acetyl Value.-Most fats and oils contain only very small
amounts of hydroxy fatty acids. Hence the acetyl value, which
measures this property, is usually negligible, as in the case of
citrus seed oils.

Reichert-Meissl Number.-By definition, this term is the
milliliters of 0.1 N alkali required to neutralize the volatile water-
soluble fatty acids distilled from 5 gm of fat or oil. The Reich-
ert-Meissl number is now obsolete and not useful for charac-
terization of most fats.
Polenske Number.-This term is a measure of the milliliters
of 0.1 N alkali required to neutralize the volatile, water-insoluble
fatty acids distilled from 5 gm of fat or oil. Like the Reichert-
Meissl number, the Polenske number is obsolete; however, both
determinations can be used in differentiating butter from coco-
nut oil and for detection of adulteration of butter. Most oils,








ity should have a very low acid value, while crude oils or oils
which have been abused have greater quantities of free fatty
acids. The presence of significant quantities of free acids in an
oil will result in lowering the smoke point, an undesirable fea-
ture if the oil is to be used for frying purposes.

Iodine Value.-The iodine value is the number of grams of
12 absorbed per 100 gm of fat or oil, based on addition to carbon-
carbon double bonds of the unsaturated fatty acids in the oil.
The iodine value increases with increasing unsaturation of an
oil and decreases with increasing melting point. Iodine value in-
creases linearly with increasing refractive index, and this rela-
tionship has been published for seed oils of the major citrus
cultivars (24).
Saponification Number.-This characteristic of seed oils is
sometimes referred to as the Koettstorfer number, a term now
in disuse. By definition, the saponification number is the milli-
grams of potassium hydroxide necessary to saponify 1 gm of
fat, and is a measure of the average length of the fatty acid
chains attached to the glycerides in a fat. Generally, the sapon-
ification value increases as the average molecular weight of the
triglycerides in a fat decreases. For example, unusually high
values are obtained from fats such as milk fat, coconut, and
palm kernel oils, which have larger amounts of short chain fatty
acids. Values for most citrus seed oils listed in Table 4 lie in
the range of 185 to 200, although one report (12) gives an ab-
normally high value for Bitter orange.
Acetyl Value.-Most fats and oils contain only very small
amounts of hydroxy fatty acids. Hence the acetyl value, which
measures this property, is usually negligible, as in the case of
citrus seed oils.

Reichert-Meissl Number.-By definition, this term is the
milliliters of 0.1 N alkali required to neutralize the volatile water-
soluble fatty acids distilled from 5 gm of fat or oil. The Reich-
ert-Meissl number is now obsolete and not useful for charac-
terization of most fats.
Polenske Number.-This term is a measure of the milliliters
of 0.1 N alkali required to neutralize the volatile, water-insoluble
fatty acids distilled from 5 gm of fat or oil. Like the Reichert-
Meissl number, the Polenske number is obsolete; however, both
determinations can be used in differentiating butter from coco-
nut oil and for detection of adulteration of butter. Most oils,








ity should have a very low acid value, while crude oils or oils
which have been abused have greater quantities of free fatty
acids. The presence of significant quantities of free acids in an
oil will result in lowering the smoke point, an undesirable fea-
ture if the oil is to be used for frying purposes.

Iodine Value.-The iodine value is the number of grams of
12 absorbed per 100 gm of fat or oil, based on addition to carbon-
carbon double bonds of the unsaturated fatty acids in the oil.
The iodine value increases with increasing unsaturation of an
oil and decreases with increasing melting point. Iodine value in-
creases linearly with increasing refractive index, and this rela-
tionship has been published for seed oils of the major citrus
cultivars (24).
Saponification Number.-This characteristic of seed oils is
sometimes referred to as the Koettstorfer number, a term now
in disuse. By definition, the saponification number is the milli-
grams of potassium hydroxide necessary to saponify 1 gm of
fat, and is a measure of the average length of the fatty acid
chains attached to the glycerides in a fat. Generally, the sapon-
ification value increases as the average molecular weight of the
triglycerides in a fat decreases. For example, unusually high
values are obtained from fats such as milk fat, coconut, and
palm kernel oils, which have larger amounts of short chain fatty
acids. Values for most citrus seed oils listed in Table 4 lie in
the range of 185 to 200, although one report (12) gives an ab-
normally high value for Bitter orange.
Acetyl Value.-Most fats and oils contain only very small
amounts of hydroxy fatty acids. Hence the acetyl value, which
measures this property, is usually negligible, as in the case of
citrus seed oils.

Reichert-Meissl Number.-By definition, this term is the
milliliters of 0.1 N alkali required to neutralize the volatile water-
soluble fatty acids distilled from 5 gm of fat or oil. The Reich-
ert-Meissl number is now obsolete and not useful for charac-
terization of most fats.
Polenske Number.-This term is a measure of the milliliters
of 0.1 N alkali required to neutralize the volatile, water-insoluble
fatty acids distilled from 5 gm of fat or oil. Like the Reichert-
Meissl number, the Polenske number is obsolete; however, both
determinations can be used in differentiating butter from coco-
nut oil and for detection of adulteration of butter. Most oils,








ity should have a very low acid value, while crude oils or oils
which have been abused have greater quantities of free fatty
acids. The presence of significant quantities of free acids in an
oil will result in lowering the smoke point, an undesirable fea-
ture if the oil is to be used for frying purposes.

Iodine Value.-The iodine value is the number of grams of
12 absorbed per 100 gm of fat or oil, based on addition to carbon-
carbon double bonds of the unsaturated fatty acids in the oil.
The iodine value increases with increasing unsaturation of an
oil and decreases with increasing melting point. Iodine value in-
creases linearly with increasing refractive index, and this rela-
tionship has been published for seed oils of the major citrus
cultivars (24).
Saponification Number.-This characteristic of seed oils is
sometimes referred to as the Koettstorfer number, a term now
in disuse. By definition, the saponification number is the milli-
grams of potassium hydroxide necessary to saponify 1 gm of
fat, and is a measure of the average length of the fatty acid
chains attached to the glycerides in a fat. Generally, the sapon-
ification value increases as the average molecular weight of the
triglycerides in a fat decreases. For example, unusually high
values are obtained from fats such as milk fat, coconut, and
palm kernel oils, which have larger amounts of short chain fatty
acids. Values for most citrus seed oils listed in Table 4 lie in
the range of 185 to 200, although one report (12) gives an ab-
normally high value for Bitter orange.
Acetyl Value.-Most fats and oils contain only very small
amounts of hydroxy fatty acids. Hence the acetyl value, which
measures this property, is usually negligible, as in the case of
citrus seed oils.

Reichert-Meissl Number.-By definition, this term is the
milliliters of 0.1 N alkali required to neutralize the volatile water-
soluble fatty acids distilled from 5 gm of fat or oil. The Reich-
ert-Meissl number is now obsolete and not useful for charac-
terization of most fats.
Polenske Number.-This term is a measure of the milliliters
of 0.1 N alkali required to neutralize the volatile, water-insoluble
fatty acids distilled from 5 gm of fat or oil. Like the Reichert-
Meissl number, the Polenske number is obsolete; however, both
determinations can be used in differentiating butter from coco-
nut oil and for detection of adulteration of butter. Most oils,








ity should have a very low acid value, while crude oils or oils
which have been abused have greater quantities of free fatty
acids. The presence of significant quantities of free acids in an
oil will result in lowering the smoke point, an undesirable fea-
ture if the oil is to be used for frying purposes.

Iodine Value.-The iodine value is the number of grams of
12 absorbed per 100 gm of fat or oil, based on addition to carbon-
carbon double bonds of the unsaturated fatty acids in the oil.
The iodine value increases with increasing unsaturation of an
oil and decreases with increasing melting point. Iodine value in-
creases linearly with increasing refractive index, and this rela-
tionship has been published for seed oils of the major citrus
cultivars (24).
Saponification Number.-This characteristic of seed oils is
sometimes referred to as the Koettstorfer number, a term now
in disuse. By definition, the saponification number is the milli-
grams of potassium hydroxide necessary to saponify 1 gm of
fat, and is a measure of the average length of the fatty acid
chains attached to the glycerides in a fat. Generally, the sapon-
ification value increases as the average molecular weight of the
triglycerides in a fat decreases. For example, unusually high
values are obtained from fats such as milk fat, coconut, and
palm kernel oils, which have larger amounts of short chain fatty
acids. Values for most citrus seed oils listed in Table 4 lie in
the range of 185 to 200, although one report (12) gives an ab-
normally high value for Bitter orange.
Acetyl Value.-Most fats and oils contain only very small
amounts of hydroxy fatty acids. Hence the acetyl value, which
measures this property, is usually negligible, as in the case of
citrus seed oils.

Reichert-Meissl Number.-By definition, this term is the
milliliters of 0.1 N alkali required to neutralize the volatile water-
soluble fatty acids distilled from 5 gm of fat or oil. The Reich-
ert-Meissl number is now obsolete and not useful for charac-
terization of most fats.
Polenske Number.-This term is a measure of the milliliters
of 0.1 N alkali required to neutralize the volatile, water-insoluble
fatty acids distilled from 5 gm of fat or oil. Like the Reichert-
Meissl number, the Polenske number is obsolete; however, both
determinations can be used in differentiating butter from coco-
nut oil and for detection of adulteration of butter. Most oils,











Table 4. Seed Oil Characteristics from Various Authors.

Specific Refractive Acid Iodine Sap. Acetyl Reichert- Polenske Hehner
Cultivar Gravity Index Value Value Value Value Meissl No. No. Value
ran- (1 ) 09251 14714 269 97.34 196.56 0.88 0.40 95.55


Valencia Orange (51)
Sweet Orange (53)
Bitter Orange (12)
Bitter Orange (43)
Grapefruit (37)
Grapefruit (28)
Shaddock (42)
Tangerine (46)
Mandarin (10)
Lemon (41)
Lemon (13)
Calamondin (1)
Cottonseed (8)
Soybean (8)


0.9153
0.9196
0.9236


0.9197
0.9170
0.9086
0.9165
0.9123


0.9000
0.9061
0.9170
0.9180


1.4686
1.4683
1.4649
1.4608
1.4698
1.4700
1.4645
1.4702
1.4693
1.4706*


1.4610
1.4630
1.4720


1.18
4.36


0.95
2.5
1.54
4.31
1.52


1.75
0.45


101.7
98.37
86.05
98.9
100.9
106.3
92.7
107.30
94.10
109.2
107.26
96.8
109.2


- 130.0


197.5
192.0
238.7
193.6
193.0
194.1
189.7
193.55
194.00
188.35
195.98
187.49
194.60
192.00


- 0.39


0.47


*Refractive index from reference (25).


0.30


0.53


95.57
95.6







including citrus seed oil, have Reichert-Meissl and Polenske
values of less than unity.
Hehner Value.-This determination measures the amount of
fatty acids that are insoluble in water; and since most fatty
acids present in natural fats are not water soluble, these fats
have high Hehner values. Again, this term is not now generally
in use.
Processing
The processing procedure for citrus seed oil production which
has previously been in use in Florida has been described in part
by Hendrickson and Kesterson (27) and by the USDA, Agri-
cultural Research Service (50). Separation of seeds from the
peel, rag and pulp, or juice sacs may be accomplished in several
ways. By one method, the seed-containing material is dropped
into a rotating reel fixed with a coarse screen, and the finer ma-
terial (seeds and juice sacs) falls through the openings. Juice
sacs and small pieces of rag are separated from the seeds by a
paddle finisher. The recovered seeds are then limed and dried
to a moisture content of approximately 10% prior to extraction
of oil.
A novel procedure for the separation of citrus seeds from
refuse material has been developed by W. A. Kirk (Patent
#3,330,410, July 11, 1967) of the Imperial Citrus By-Products
Corp., Lakeland, Florida (now defunct). This method is pre-
ferred, since whole refuse consisting of peel, rag, pulp, and seeds
-or, preferably, a mixture of pulp and seeds-can be separated.
The refuse material is transferred by a screw conveyor to a
scrambling device, which throws and distributes the material
evenly onto a slanted (30' slope) moving belt. At the instant
of contact, the seeds bounce off the belt, striking a baffle which
diverts them into a storage bin. The descending refuse is col-
lected at the end of the conveyor. Depending on the nature of
the refuse, wet or dry, a seed removal efficiency of some 60% to
80% is effected, the most efficient separation coming from rela-
tively dry refuse. The primary advantage of this system is a
relatively low initial cost, permitting the removal of seeds with-
out creating the waste water pollution problem normally en-
countered in the separation of seeds by screens or finishers. A
sufficient quantity of lime (0.15% to 0.25% Ca(OH)2) is added
to the seeds in the storage bin to prevent them from solidifying
(gel formation). The limed seeds are normally transported by
truck to a central collection point where they are dried, stored,
or processed.







including citrus seed oil, have Reichert-Meissl and Polenske
values of less than unity.
Hehner Value.-This determination measures the amount of
fatty acids that are insoluble in water; and since most fatty
acids present in natural fats are not water soluble, these fats
have high Hehner values. Again, this term is not now generally
in use.
Processing
The processing procedure for citrus seed oil production which
has previously been in use in Florida has been described in part
by Hendrickson and Kesterson (27) and by the USDA, Agri-
cultural Research Service (50). Separation of seeds from the
peel, rag and pulp, or juice sacs may be accomplished in several
ways. By one method, the seed-containing material is dropped
into a rotating reel fixed with a coarse screen, and the finer ma-
terial (seeds and juice sacs) falls through the openings. Juice
sacs and small pieces of rag are separated from the seeds by a
paddle finisher. The recovered seeds are then limed and dried
to a moisture content of approximately 10% prior to extraction
of oil.
A novel procedure for the separation of citrus seeds from
refuse material has been developed by W. A. Kirk (Patent
#3,330,410, July 11, 1967) of the Imperial Citrus By-Products
Corp., Lakeland, Florida (now defunct). This method is pre-
ferred, since whole refuse consisting of peel, rag, pulp, and seeds
-or, preferably, a mixture of pulp and seeds-can be separated.
The refuse material is transferred by a screw conveyor to a
scrambling device, which throws and distributes the material
evenly onto a slanted (30' slope) moving belt. At the instant
of contact, the seeds bounce off the belt, striking a baffle which
diverts them into a storage bin. The descending refuse is col-
lected at the end of the conveyor. Depending on the nature of
the refuse, wet or dry, a seed removal efficiency of some 60% to
80% is effected, the most efficient separation coming from rela-
tively dry refuse. The primary advantage of this system is a
relatively low initial cost, permitting the removal of seeds with-
out creating the waste water pollution problem normally en-
countered in the separation of seeds by screens or finishers. A
sufficient quantity of lime (0.15% to 0.25% Ca(OH)2) is added
to the seeds in the storage bin to prevent them from solidifying
(gel formation). The limed seeds are normally transported by
truck to a central collection point where they are dried, stored,
or processed.








An alternative method for collecting seeds is to lime the
mixture of peel, rag, pulp, and seeds and dry in the conventional
manner for the preparation of livestock feed. The dried seeds
have a greater density than the dried peel, rag, or pulp and may
be effectively separated by a system of cyclone separators,
screens, and winnowing devices (50). The main disadvantage
of this process is the high initial cost for equipment. Seeds sep-
arated by this procedure are quite likely to have a moisture con-
tent that is higher than that required for safe storage (8% to
10%) and would require additional drying.
The percentages (wt/wt) of wet seeds in the whole fruit of
most varieties are averages obtained for one entire processing
season (Table 2). These percentages are generally higher for
immature fruit and lower for mature fruit, as shown in Table 5.
Variation in the juice weight is responsible for this difference,
since we found the seed weight to be rather constant through-
out a season. Season to season variation in the percent (wt/wt)
of wet seeds in the whole fruit is also small for Duncan grape-


Table 5. Percentage (wt/wt) of seeds in Citrus and the related percentage in
the corresponding dried pulp for a season.

Seeds in Grapefruit Seeds in Oranges
Variety and Whole Dried Variety and Whole Dried
Month of Season Fruit (%) Pulp (%) Month of Season Fruit (%) Pulp (%)

Duncan Pineapple
October 6.8 18.7 October 5.2 14.2
December 4.8 15.2 December 3.2 11.2
February 4.3 13.9 February 3.1 11.2
April 2.9 11.2 April 2.7 10.2

Foster Pink Parson Brown
October 5.0 10.4 October 3.5 9.5
December 4.1 11.5 December 2.4 7.5
February 3.1 11.1 February 2.2 8.5
April 2.6 10.9 April 1.7 7.0

Marsh Valencia
October 0.5 1.7 October 1.2 3.5
December 0.3 1.9 December 0.8 3.2
February 0.3 1.8 February 0.7 3.2
April 0.3 2.2 April 0.7 3.2







fruit (2%) as well as for Pineapple (1%) and Valencia oranges
(0.5%), the only three varieties for which data was available
during more than one season. These three varieties are the
major source of seeds for oil processing from the Florida citrus
industry.
Dehulling.-Most oil seeds are preferably decorticated prior
to extraction of the oil. If the hulls are not removed from the
seeds before extraction, they may reduce the total yield of oil
by absorbing and retaining oil in the press cake and, in addition,
reduce the capacity of the extraction equipment. In practical
operation, the greatest yield of oil should be obtained by balanc-
ing the degree of separation of hulls and kernels. If an attempt
is made to separate hulls from the meats too cleanly, there will
be a loss of oil due to meats being carried over into the hulls.
If excessive proportions of hulls are left among the kernels,
there will likewise be an undue loss of oil from absorption by
the hulls (8). However, in some trials of continuous expelling
of the oil from Valencia orange seed kernels, it was shown that
the kernels did not press as well alone as when mixed with
shredded hulls (51).
Reduction.-The extraction of oil from oil seeds, either by
mechanical expression or by solvents, is facilitated by reduction
of the oil bearing kernel to small particles or flakes (8). With
citrus seeds, solvent extraction of the oil has not been practiced
in the Florida industry, most of the oil being produced by ex-
pression in expellers or screw presses. (See Figure 1.) During
the preparation of oil seeds for expression in expellers, reduction
of the kernels, as in flaking, is not as necessary as for solvent
extraction, since heat is generated and seed particles are broken
up by the intense shearing stresses developed in the barrel of
the expeller (8).
Cooking.-The primary objective of cooking oil seeds is to
increase the oil yield, particularly if the oil is expressed mechan-
ically. The moisture content of the seed may be controlled by
cooking, and is important to the yield of oil obtained. Very dry
seeds cannot be efficiently freed of their oil. The optimum mois-
ture of cooked oil seeds depends on the type of seed and the
method by which the oil is expressed. The optimum moisture
for expression of oil from citrus seeds is not known, but it has
been the practice to dry the seeds in a direct flame dryer to 6%
to 10% moisture prior to oil expression (37, 51). Cooking of dried
citrus seeds has not been practiced in Florida but would be rec-
ommended if the oil is expressed mechanically. This operation







fruit (2%) as well as for Pineapple (1%) and Valencia oranges
(0.5%), the only three varieties for which data was available
during more than one season. These three varieties are the
major source of seeds for oil processing from the Florida citrus
industry.
Dehulling.-Most oil seeds are preferably decorticated prior
to extraction of the oil. If the hulls are not removed from the
seeds before extraction, they may reduce the total yield of oil
by absorbing and retaining oil in the press cake and, in addition,
reduce the capacity of the extraction equipment. In practical
operation, the greatest yield of oil should be obtained by balanc-
ing the degree of separation of hulls and kernels. If an attempt
is made to separate hulls from the meats too cleanly, there will
be a loss of oil due to meats being carried over into the hulls.
If excessive proportions of hulls are left among the kernels,
there will likewise be an undue loss of oil from absorption by
the hulls (8). However, in some trials of continuous expelling
of the oil from Valencia orange seed kernels, it was shown that
the kernels did not press as well alone as when mixed with
shredded hulls (51).
Reduction.-The extraction of oil from oil seeds, either by
mechanical expression or by solvents, is facilitated by reduction
of the oil bearing kernel to small particles or flakes (8). With
citrus seeds, solvent extraction of the oil has not been practiced
in the Florida industry, most of the oil being produced by ex-
pression in expellers or screw presses. (See Figure 1.) During
the preparation of oil seeds for expression in expellers, reduction
of the kernels, as in flaking, is not as necessary as for solvent
extraction, since heat is generated and seed particles are broken
up by the intense shearing stresses developed in the barrel of
the expeller (8).
Cooking.-The primary objective of cooking oil seeds is to
increase the oil yield, particularly if the oil is expressed mechan-
ically. The moisture content of the seed may be controlled by
cooking, and is important to the yield of oil obtained. Very dry
seeds cannot be efficiently freed of their oil. The optimum mois-
ture of cooked oil seeds depends on the type of seed and the
method by which the oil is expressed. The optimum moisture
for expression of oil from citrus seeds is not known, but it has
been the practice to dry the seeds in a direct flame dryer to 6%
to 10% moisture prior to oil expression (37, 51). Cooking of dried
citrus seeds has not been practiced in Florida but would be rec-
ommended if the oil is expressed mechanically. This operation







fruit (2%) as well as for Pineapple (1%) and Valencia oranges
(0.5%), the only three varieties for which data was available
during more than one season. These three varieties are the
major source of seeds for oil processing from the Florida citrus
industry.
Dehulling.-Most oil seeds are preferably decorticated prior
to extraction of the oil. If the hulls are not removed from the
seeds before extraction, they may reduce the total yield of oil
by absorbing and retaining oil in the press cake and, in addition,
reduce the capacity of the extraction equipment. In practical
operation, the greatest yield of oil should be obtained by balanc-
ing the degree of separation of hulls and kernels. If an attempt
is made to separate hulls from the meats too cleanly, there will
be a loss of oil due to meats being carried over into the hulls.
If excessive proportions of hulls are left among the kernels,
there will likewise be an undue loss of oil from absorption by
the hulls (8). However, in some trials of continuous expelling
of the oil from Valencia orange seed kernels, it was shown that
the kernels did not press as well alone as when mixed with
shredded hulls (51).
Reduction.-The extraction of oil from oil seeds, either by
mechanical expression or by solvents, is facilitated by reduction
of the oil bearing kernel to small particles or flakes (8). With
citrus seeds, solvent extraction of the oil has not been practiced
in the Florida industry, most of the oil being produced by ex-
pression in expellers or screw presses. (See Figure 1.) During
the preparation of oil seeds for expression in expellers, reduction
of the kernels, as in flaking, is not as necessary as for solvent
extraction, since heat is generated and seed particles are broken
up by the intense shearing stresses developed in the barrel of
the expeller (8).
Cooking.-The primary objective of cooking oil seeds is to
increase the oil yield, particularly if the oil is expressed mechan-
ically. The moisture content of the seed may be controlled by
cooking, and is important to the yield of oil obtained. Very dry
seeds cannot be efficiently freed of their oil. The optimum mois-
ture of cooked oil seeds depends on the type of seed and the
method by which the oil is expressed. The optimum moisture
for expression of oil from citrus seeds is not known, but it has
been the practice to dry the seeds in a direct flame dryer to 6%
to 10% moisture prior to oil expression (37, 51). Cooking of dried
citrus seeds has not been practiced in Florida but would be rec-
ommended if the oil is expressed mechanically. This operation








MATERIAL


Figure 1. Schematic of an Anderson expeller. (Courtesy of V. H. Anderson
Company, Cleveland, Ohio.)


may be carried out in the steam jacketed kettles such as the
stack cooker shown in Figure 2. Preliminary experiments with
citrus seeds showed that satisfactory expelling could be accom-
plished if the meal was cooked to about 220 F (51).
Oil Expression and Extraction.-While the oil from citrus
seeds has been removed by expression in an expeller (Figure 1),
the minimum oil content to which oil cake can be reduced by this
method is approximately 2% to 3%. To remove this 2% to 3%
of oil, it would be necessary to use some type of solvent extrac-
tion. If solvent extraction of citrus seeds is to be used, it may
be in conjunction with expelling, as the oil content of the whole
seed is about 40% on a dry basis. Operations such as flaking
will be necessary, since efficiency of solvent extraction is much
more dependent upon particle size or flake thickness than is
mechanical expression. For soybeans, commercial solvent ex-
tractions with hexane commonly reduce the oil content of the
dry solid residue meal to about 0.5%.
Refining.-Citrus seed oil is not refined in Florida, but sold
as crude oil to out-of-state manufacturers, who may then refine
it. Refining is necessary if the oil is to be used for edible pur-
poses, since the crude oil contains nonglyceride impurities such
as free fatty acids, phosphatides, pigments, and bitter materials








MATERIAL


Figure 1. Schematic of an Anderson expeller. (Courtesy of V. H. Anderson
Company, Cleveland, Ohio.)


may be carried out in the steam jacketed kettles such as the
stack cooker shown in Figure 2. Preliminary experiments with
citrus seeds showed that satisfactory expelling could be accom-
plished if the meal was cooked to about 220 F (51).
Oil Expression and Extraction.-While the oil from citrus
seeds has been removed by expression in an expeller (Figure 1),
the minimum oil content to which oil cake can be reduced by this
method is approximately 2% to 3%. To remove this 2% to 3%
of oil, it would be necessary to use some type of solvent extrac-
tion. If solvent extraction of citrus seeds is to be used, it may
be in conjunction with expelling, as the oil content of the whole
seed is about 40% on a dry basis. Operations such as flaking
will be necessary, since efficiency of solvent extraction is much
more dependent upon particle size or flake thickness than is
mechanical expression. For soybeans, commercial solvent ex-
tractions with hexane commonly reduce the oil content of the
dry solid residue meal to about 0.5%.
Refining.-Citrus seed oil is not refined in Florida, but sold
as crude oil to out-of-state manufacturers, who may then refine
it. Refining is necessary if the oil is to be used for edible pur-
poses, since the crude oil contains nonglyceride impurities such
as free fatty acids, phosphatides, pigments, and bitter materials







like limonin and naringin. Refining is commonly done by treat-
ment of the crude oil with a slight excess of alkali over the
amount necessary to react with the free fatty acids in the oil.
Experiments in our laboratory on commercial crude citrus
seed oils have shown free fatty acid contents of 0.3% to 1.4%.
Refining losses determined by a standard A.O.C.S. procedure
(2), Method Ca 9f 57, were 0.8% to 3.5% depending on the
initial free fatty acid content. Economies of losses through re-
fining should dictate that crude citrus seed oils must be produced
with the lowest possible content of free fatty acids and other


* ~: :jjc ~.: I


-~.-~ --


Figure 2. Phantom view of four-high stack cooker and shaft arrangement of
a continuous mechanical screw press. (Courtesy of the French
Oil Mill Machinery Co., Piqua, Ohio.)

15


-I -







impurities such as phosphatides. This means that care should
be taken to regulate heat treatment and moisture content of
the seeds prior to processing and expression of the oil.
Limonin Recovery from Crude Oil.-Isolation of the bitter
principle, limonin, from grapefruit seed oil has been described
by Nolte et al. (37). This procedure entailed acidifying the soap
stock obtained in refining the crude oil, followed by extraction
with benzene. The limonin was precipitated by addition of three
volumes of petroleum ether to the benzene extract. The precip-
itate was purified by a combination of filtration, washing with
petroleum ether and glacial acetic acid, recrystallization, boiling
with water, filtration, and washing free from acid.
Degumming.-Improper handling of the crude oil after ex-
pression or extraction will also contribute to refining losses and
poorer quality of the refined oil. In cases of high refining losses,
many crude oils, such as soybean oils, are degummed. Degum-
ming is accomplished by adding water to the crude oil to hydrate
the phosphatides (primarily lecithin), making them insoluble in
the oil. The hydrated phosphatides can then be removed by cen-
trifugation. Degumming of crude citrus seed oils (phosphatide
content 0.3% to 1.1%) should be performed prior to shipping or
storage of the oils to prevent trouble from gums settling in stor-
age tanks and tank cars. A market may be developed for the
lecithin and phosphatides from the degumming operation of
citrus seed oils, since the gums can be used to increase oil con-
tent, minimize dustiness, and facilitate pelleting of the seed
meal.
Bleaching.-Since refining of citrus seed oils is not performed
in Florida, bleaching is not an important consideration to the
citrus industry. However, treatment of the crude oil during
processing should not lead to poor quality oils, which would be
difficult to bleach. Bleaching is accomplished by adsorption with
standard bleaching earths or clay, and removes from the oil
pigments and other oxygenated materials which contribute to
color.
Deodorizing.-Bleaching and deodorization are usually con-
sidered part of the refining process. Deodorization of oils is
usually effected by steam treatment under vacuum following
alkali refining and bleaching. This process is intended to pro-
duce bland, odorless, and tastless fats and oils and removes
many natural and foreign flavors and free fatty acids from the
oil. Refining, bleaching, and deodorization of citrus seed oil were







impurities such as phosphatides. This means that care should
be taken to regulate heat treatment and moisture content of
the seeds prior to processing and expression of the oil.
Limonin Recovery from Crude Oil.-Isolation of the bitter
principle, limonin, from grapefruit seed oil has been described
by Nolte et al. (37). This procedure entailed acidifying the soap
stock obtained in refining the crude oil, followed by extraction
with benzene. The limonin was precipitated by addition of three
volumes of petroleum ether to the benzene extract. The precip-
itate was purified by a combination of filtration, washing with
petroleum ether and glacial acetic acid, recrystallization, boiling
with water, filtration, and washing free from acid.
Degumming.-Improper handling of the crude oil after ex-
pression or extraction will also contribute to refining losses and
poorer quality of the refined oil. In cases of high refining losses,
many crude oils, such as soybean oils, are degummed. Degum-
ming is accomplished by adding water to the crude oil to hydrate
the phosphatides (primarily lecithin), making them insoluble in
the oil. The hydrated phosphatides can then be removed by cen-
trifugation. Degumming of crude citrus seed oils (phosphatide
content 0.3% to 1.1%) should be performed prior to shipping or
storage of the oils to prevent trouble from gums settling in stor-
age tanks and tank cars. A market may be developed for the
lecithin and phosphatides from the degumming operation of
citrus seed oils, since the gums can be used to increase oil con-
tent, minimize dustiness, and facilitate pelleting of the seed
meal.
Bleaching.-Since refining of citrus seed oils is not performed
in Florida, bleaching is not an important consideration to the
citrus industry. However, treatment of the crude oil during
processing should not lead to poor quality oils, which would be
difficult to bleach. Bleaching is accomplished by adsorption with
standard bleaching earths or clay, and removes from the oil
pigments and other oxygenated materials which contribute to
color.
Deodorizing.-Bleaching and deodorization are usually con-
sidered part of the refining process. Deodorization of oils is
usually effected by steam treatment under vacuum following
alkali refining and bleaching. This process is intended to pro-
duce bland, odorless, and tastless fats and oils and removes
many natural and foreign flavors and free fatty acids from the
oil. Refining, bleaching, and deodorization of citrus seed oil were







impurities such as phosphatides. This means that care should
be taken to regulate heat treatment and moisture content of
the seeds prior to processing and expression of the oil.
Limonin Recovery from Crude Oil.-Isolation of the bitter
principle, limonin, from grapefruit seed oil has been described
by Nolte et al. (37). This procedure entailed acidifying the soap
stock obtained in refining the crude oil, followed by extraction
with benzene. The limonin was precipitated by addition of three
volumes of petroleum ether to the benzene extract. The precip-
itate was purified by a combination of filtration, washing with
petroleum ether and glacial acetic acid, recrystallization, boiling
with water, filtration, and washing free from acid.
Degumming.-Improper handling of the crude oil after ex-
pression or extraction will also contribute to refining losses and
poorer quality of the refined oil. In cases of high refining losses,
many crude oils, such as soybean oils, are degummed. Degum-
ming is accomplished by adding water to the crude oil to hydrate
the phosphatides (primarily lecithin), making them insoluble in
the oil. The hydrated phosphatides can then be removed by cen-
trifugation. Degumming of crude citrus seed oils (phosphatide
content 0.3% to 1.1%) should be performed prior to shipping or
storage of the oils to prevent trouble from gums settling in stor-
age tanks and tank cars. A market may be developed for the
lecithin and phosphatides from the degumming operation of
citrus seed oils, since the gums can be used to increase oil con-
tent, minimize dustiness, and facilitate pelleting of the seed
meal.
Bleaching.-Since refining of citrus seed oils is not performed
in Florida, bleaching is not an important consideration to the
citrus industry. However, treatment of the crude oil during
processing should not lead to poor quality oils, which would be
difficult to bleach. Bleaching is accomplished by adsorption with
standard bleaching earths or clay, and removes from the oil
pigments and other oxygenated materials which contribute to
color.
Deodorizing.-Bleaching and deodorization are usually con-
sidered part of the refining process. Deodorization of oils is
usually effected by steam treatment under vacuum following
alkali refining and bleaching. This process is intended to pro-
duce bland, odorless, and tastless fats and oils and removes
many natural and foreign flavors and free fatty acids from the
oil. Refining, bleaching, and deodorization of citrus seed oil were







impurities such as phosphatides. This means that care should
be taken to regulate heat treatment and moisture content of
the seeds prior to processing and expression of the oil.
Limonin Recovery from Crude Oil.-Isolation of the bitter
principle, limonin, from grapefruit seed oil has been described
by Nolte et al. (37). This procedure entailed acidifying the soap
stock obtained in refining the crude oil, followed by extraction
with benzene. The limonin was precipitated by addition of three
volumes of petroleum ether to the benzene extract. The precip-
itate was purified by a combination of filtration, washing with
petroleum ether and glacial acetic acid, recrystallization, boiling
with water, filtration, and washing free from acid.
Degumming.-Improper handling of the crude oil after ex-
pression or extraction will also contribute to refining losses and
poorer quality of the refined oil. In cases of high refining losses,
many crude oils, such as soybean oils, are degummed. Degum-
ming is accomplished by adding water to the crude oil to hydrate
the phosphatides (primarily lecithin), making them insoluble in
the oil. The hydrated phosphatides can then be removed by cen-
trifugation. Degumming of crude citrus seed oils (phosphatide
content 0.3% to 1.1%) should be performed prior to shipping or
storage of the oils to prevent trouble from gums settling in stor-
age tanks and tank cars. A market may be developed for the
lecithin and phosphatides from the degumming operation of
citrus seed oils, since the gums can be used to increase oil con-
tent, minimize dustiness, and facilitate pelleting of the seed
meal.
Bleaching.-Since refining of citrus seed oils is not performed
in Florida, bleaching is not an important consideration to the
citrus industry. However, treatment of the crude oil during
processing should not lead to poor quality oils, which would be
difficult to bleach. Bleaching is accomplished by adsorption with
standard bleaching earths or clay, and removes from the oil
pigments and other oxygenated materials which contribute to
color.
Deodorizing.-Bleaching and deodorization are usually con-
sidered part of the refining process. Deodorization of oils is
usually effected by steam treatment under vacuum following
alkali refining and bleaching. This process is intended to pro-
duce bland, odorless, and tastless fats and oils and removes
many natural and foreign flavors and free fatty acids from the
oil. Refining, bleaching, and deodorization of citrus seed oil were







shown to remove most of the bitterness caused by limonin, and
to produce a bland and pleasant tasting oil (51).
Winterization.-Edible oils that will remain liquid at tem-
peratures around 450 F are preferred in the U.S. because of
widespread use of refrigeration and air-conditioning. Winter-
ization of cottonseed oil is commonly performed to remove
higher-melting triglycerides which contribute to haze formation
in the oil. Usually, the refined oil is slowly cooled (in 12 to 15
hr.) to about 400 F, causing the triglyceride crystals to pre-
cipitate. The oil is then filtered to remove the crystals. Some
oils also may be chilled to remove traces of waxes and gums
which cause cloudiness. The physical characteristics of winter-
ized grapefruit seed oil (Iodine No. 109) have been published
(37), describing the oil as light yellow in color.
Hydrogenation.-The possibility exists of producing a line of
specialty fat products, made entirely from citrus seed oils. The
market interest in these products would come from the general
appeal of pure citrus products and juices. Production of such
products as citrus margarine, salad oils, and mayonnaise would
require alteration of the properties of the oil. Hydrogenation is
the primary means of converting liquid oils to semisolid, plastic
fats suitable for shortening or margarine manufacture. It also
enhances the stability and improves the color of the fat (8).
The reaction involves the catalytic addition of hydrogen to car-
bon-carbon double bonds in the fatty acid chains of an oil.
Interesterification.-Production of specialty fats involves
alteration of the properties of a fat, as mentioned above for
hydrogenation. Other necessary processes are fat splitting, in
which fat is hydrolyzed to free fatty acids and glycerol, and
interesterification, where the fatty acids are subjected to mo-
lecular rearrangement of the positions of the glycerides, result-
ing in changing such characteristics as melting point and plas-
ticity.
Quality Control
Some aspects of quality control in the production of fats and
oils have already been mentioned in previous sections. This
portion deals with some methods and topics which may be ap-
plicable and adapted to citrus seed oil manufacture.
Heat Treatment.-Heating of citrus seeds or kernels during
drying, cooking, and expelling of the oil was performed at prod-
uct temperatures of about 2000 F in one study (51). One Florida







shown to remove most of the bitterness caused by limonin, and
to produce a bland and pleasant tasting oil (51).
Winterization.-Edible oils that will remain liquid at tem-
peratures around 450 F are preferred in the U.S. because of
widespread use of refrigeration and air-conditioning. Winter-
ization of cottonseed oil is commonly performed to remove
higher-melting triglycerides which contribute to haze formation
in the oil. Usually, the refined oil is slowly cooled (in 12 to 15
hr.) to about 400 F, causing the triglyceride crystals to pre-
cipitate. The oil is then filtered to remove the crystals. Some
oils also may be chilled to remove traces of waxes and gums
which cause cloudiness. The physical characteristics of winter-
ized grapefruit seed oil (Iodine No. 109) have been published
(37), describing the oil as light yellow in color.
Hydrogenation.-The possibility exists of producing a line of
specialty fat products, made entirely from citrus seed oils. The
market interest in these products would come from the general
appeal of pure citrus products and juices. Production of such
products as citrus margarine, salad oils, and mayonnaise would
require alteration of the properties of the oil. Hydrogenation is
the primary means of converting liquid oils to semisolid, plastic
fats suitable for shortening or margarine manufacture. It also
enhances the stability and improves the color of the fat (8).
The reaction involves the catalytic addition of hydrogen to car-
bon-carbon double bonds in the fatty acid chains of an oil.
Interesterification.-Production of specialty fats involves
alteration of the properties of a fat, as mentioned above for
hydrogenation. Other necessary processes are fat splitting, in
which fat is hydrolyzed to free fatty acids and glycerol, and
interesterification, where the fatty acids are subjected to mo-
lecular rearrangement of the positions of the glycerides, result-
ing in changing such characteristics as melting point and plas-
ticity.
Quality Control
Some aspects of quality control in the production of fats and
oils have already been mentioned in previous sections. This
portion deals with some methods and topics which may be ap-
plicable and adapted to citrus seed oil manufacture.
Heat Treatment.-Heating of citrus seeds or kernels during
drying, cooking, and expelling of the oil was performed at prod-
uct temperatures of about 2000 F in one study (51). One Florida







shown to remove most of the bitterness caused by limonin, and
to produce a bland and pleasant tasting oil (51).
Winterization.-Edible oils that will remain liquid at tem-
peratures around 450 F are preferred in the U.S. because of
widespread use of refrigeration and air-conditioning. Winter-
ization of cottonseed oil is commonly performed to remove
higher-melting triglycerides which contribute to haze formation
in the oil. Usually, the refined oil is slowly cooled (in 12 to 15
hr.) to about 400 F, causing the triglyceride crystals to pre-
cipitate. The oil is then filtered to remove the crystals. Some
oils also may be chilled to remove traces of waxes and gums
which cause cloudiness. The physical characteristics of winter-
ized grapefruit seed oil (Iodine No. 109) have been published
(37), describing the oil as light yellow in color.
Hydrogenation.-The possibility exists of producing a line of
specialty fat products, made entirely from citrus seed oils. The
market interest in these products would come from the general
appeal of pure citrus products and juices. Production of such
products as citrus margarine, salad oils, and mayonnaise would
require alteration of the properties of the oil. Hydrogenation is
the primary means of converting liquid oils to semisolid, plastic
fats suitable for shortening or margarine manufacture. It also
enhances the stability and improves the color of the fat (8).
The reaction involves the catalytic addition of hydrogen to car-
bon-carbon double bonds in the fatty acid chains of an oil.
Interesterification.-Production of specialty fats involves
alteration of the properties of a fat, as mentioned above for
hydrogenation. Other necessary processes are fat splitting, in
which fat is hydrolyzed to free fatty acids and glycerol, and
interesterification, where the fatty acids are subjected to mo-
lecular rearrangement of the positions of the glycerides, result-
ing in changing such characteristics as melting point and plas-
ticity.
Quality Control
Some aspects of quality control in the production of fats and
oils have already been mentioned in previous sections. This
portion deals with some methods and topics which may be ap-
plicable and adapted to citrus seed oil manufacture.
Heat Treatment.-Heating of citrus seeds or kernels during
drying, cooking, and expelling of the oil was performed at prod-
uct temperatures of about 2000 F in one study (51). One Florida







shown to remove most of the bitterness caused by limonin, and
to produce a bland and pleasant tasting oil (51).
Winterization.-Edible oils that will remain liquid at tem-
peratures around 450 F are preferred in the U.S. because of
widespread use of refrigeration and air-conditioning. Winter-
ization of cottonseed oil is commonly performed to remove
higher-melting triglycerides which contribute to haze formation
in the oil. Usually, the refined oil is slowly cooled (in 12 to 15
hr.) to about 400 F, causing the triglyceride crystals to pre-
cipitate. The oil is then filtered to remove the crystals. Some
oils also may be chilled to remove traces of waxes and gums
which cause cloudiness. The physical characteristics of winter-
ized grapefruit seed oil (Iodine No. 109) have been published
(37), describing the oil as light yellow in color.
Hydrogenation.-The possibility exists of producing a line of
specialty fat products, made entirely from citrus seed oils. The
market interest in these products would come from the general
appeal of pure citrus products and juices. Production of such
products as citrus margarine, salad oils, and mayonnaise would
require alteration of the properties of the oil. Hydrogenation is
the primary means of converting liquid oils to semisolid, plastic
fats suitable for shortening or margarine manufacture. It also
enhances the stability and improves the color of the fat (8).
The reaction involves the catalytic addition of hydrogen to car-
bon-carbon double bonds in the fatty acid chains of an oil.
Interesterification.-Production of specialty fats involves
alteration of the properties of a fat, as mentioned above for
hydrogenation. Other necessary processes are fat splitting, in
which fat is hydrolyzed to free fatty acids and glycerol, and
interesterification, where the fatty acids are subjected to mo-
lecular rearrangement of the positions of the glycerides, result-
ing in changing such characteristics as melting point and plas-
ticity.
Quality Control
Some aspects of quality control in the production of fats and
oils have already been mentioned in previous sections. This
portion deals with some methods and topics which may be ap-
plicable and adapted to citrus seed oil manufacture.
Heat Treatment.-Heating of citrus seeds or kernels during
drying, cooking, and expelling of the oil was performed at prod-
uct temperatures of about 2000 F in one study (51). One Florida







shown to remove most of the bitterness caused by limonin, and
to produce a bland and pleasant tasting oil (51).
Winterization.-Edible oils that will remain liquid at tem-
peratures around 450 F are preferred in the U.S. because of
widespread use of refrigeration and air-conditioning. Winter-
ization of cottonseed oil is commonly performed to remove
higher-melting triglycerides which contribute to haze formation
in the oil. Usually, the refined oil is slowly cooled (in 12 to 15
hr.) to about 400 F, causing the triglyceride crystals to pre-
cipitate. The oil is then filtered to remove the crystals. Some
oils also may be chilled to remove traces of waxes and gums
which cause cloudiness. The physical characteristics of winter-
ized grapefruit seed oil (Iodine No. 109) have been published
(37), describing the oil as light yellow in color.
Hydrogenation.-The possibility exists of producing a line of
specialty fat products, made entirely from citrus seed oils. The
market interest in these products would come from the general
appeal of pure citrus products and juices. Production of such
products as citrus margarine, salad oils, and mayonnaise would
require alteration of the properties of the oil. Hydrogenation is
the primary means of converting liquid oils to semisolid, plastic
fats suitable for shortening or margarine manufacture. It also
enhances the stability and improves the color of the fat (8).
The reaction involves the catalytic addition of hydrogen to car-
bon-carbon double bonds in the fatty acid chains of an oil.
Interesterification.-Production of specialty fats involves
alteration of the properties of a fat, as mentioned above for
hydrogenation. Other necessary processes are fat splitting, in
which fat is hydrolyzed to free fatty acids and glycerol, and
interesterification, where the fatty acids are subjected to mo-
lecular rearrangement of the positions of the glycerides, result-
ing in changing such characteristics as melting point and plas-
ticity.
Quality Control
Some aspects of quality control in the production of fats and
oils have already been mentioned in previous sections. This
portion deals with some methods and topics which may be ap-
plicable and adapted to citrus seed oil manufacture.
Heat Treatment.-Heating of citrus seeds or kernels during
drying, cooking, and expelling of the oil was performed at prod-
uct temperatures of about 2000 F in one study (51). One Florida







manufacturer produced crude oils from seeds dried in an open
flame dryer at exit stack gas temperatures of about 2500 F
(personal communication). The authors recommend exit stack
gas temperatures no higher than 2300 F, as seed kernels dried
in our pilot plant feed mill at temperatures above this value
were darkened and produced a dark brown oil of poor quality.

Color.-Color of fats and oils may be determined either by
standard A.O.C.S. procedures involving comparison of the oil
with standard color tubes, or by spectrophotometric methods
(2). The authors have found the color of commercial citrus seed
oils to be in the range of from 3 to 5, by comparison with
Gardner glass color standards (2). Crude oils of good quality
are usually light or faint yellow in color, while dark oils contain
considerable quantities of free fatty acids and are of poorer
quality.
Free Fatty Acids.-High quality seed oils contain largely
triglycerides and only small quantities of free fatty acids.
Basically, free fatty acids in the oil are a result of enzymatic
hydrolysis by lipases of the glycerides to free fatty acids and
the corresponding alcohols of the glycerides. Improper handling
of the seeds prior to or during oil extraction may result in in-
creasing the free fatty acid content in the product oil, and hence,
lowering the quality. According to analyses performed in our
laboratory, good quality crude citrus seed oils have been com-
mercially produced with less than 1 % free fatty acids. Oils with
high quantities of free fatty acids will tend to smoke if used
for frying.
Rancidity.-Fats and oils can react chemically with oxygen,
resulting in a breakdown of the fatty acids (primarily un-
saturated fatty acids) to carbonyl compounds. These compounds
may change the odor and flavor of the oil, lowering the quality.
For this reason, exposure of the oil to air during processing or
storage should be kept to a minimum, especially during any heat
treatment. Quality of an oil from a rancidity standpoint may
be evaluated in several ways. These include tasting under a
variety of conditions, peroxide determination and, in some cases,
determining the quantity of an aldehyde, malonaldehyde, which
is present in oxidized fats. We have found that citrus seed oils
readily develop rancidity, and care should be taken during man-
ufacture and storage to prevent it.

Peroxide Determination.-The presence of significant quan-
tities of peroxides is somewhat indicative that an oil has re-







manufacturer produced crude oils from seeds dried in an open
flame dryer at exit stack gas temperatures of about 2500 F
(personal communication). The authors recommend exit stack
gas temperatures no higher than 2300 F, as seed kernels dried
in our pilot plant feed mill at temperatures above this value
were darkened and produced a dark brown oil of poor quality.

Color.-Color of fats and oils may be determined either by
standard A.O.C.S. procedures involving comparison of the oil
with standard color tubes, or by spectrophotometric methods
(2). The authors have found the color of commercial citrus seed
oils to be in the range of from 3 to 5, by comparison with
Gardner glass color standards (2). Crude oils of good quality
are usually light or faint yellow in color, while dark oils contain
considerable quantities of free fatty acids and are of poorer
quality.
Free Fatty Acids.-High quality seed oils contain largely
triglycerides and only small quantities of free fatty acids.
Basically, free fatty acids in the oil are a result of enzymatic
hydrolysis by lipases of the glycerides to free fatty acids and
the corresponding alcohols of the glycerides. Improper handling
of the seeds prior to or during oil extraction may result in in-
creasing the free fatty acid content in the product oil, and hence,
lowering the quality. According to analyses performed in our
laboratory, good quality crude citrus seed oils have been com-
mercially produced with less than 1 % free fatty acids. Oils with
high quantities of free fatty acids will tend to smoke if used
for frying.
Rancidity.-Fats and oils can react chemically with oxygen,
resulting in a breakdown of the fatty acids (primarily un-
saturated fatty acids) to carbonyl compounds. These compounds
may change the odor and flavor of the oil, lowering the quality.
For this reason, exposure of the oil to air during processing or
storage should be kept to a minimum, especially during any heat
treatment. Quality of an oil from a rancidity standpoint may
be evaluated in several ways. These include tasting under a
variety of conditions, peroxide determination and, in some cases,
determining the quantity of an aldehyde, malonaldehyde, which
is present in oxidized fats. We have found that citrus seed oils
readily develop rancidity, and care should be taken during man-
ufacture and storage to prevent it.

Peroxide Determination.-The presence of significant quan-
tities of peroxides is somewhat indicative that an oil has re-







manufacturer produced crude oils from seeds dried in an open
flame dryer at exit stack gas temperatures of about 2500 F
(personal communication). The authors recommend exit stack
gas temperatures no higher than 2300 F, as seed kernels dried
in our pilot plant feed mill at temperatures above this value
were darkened and produced a dark brown oil of poor quality.

Color.-Color of fats and oils may be determined either by
standard A.O.C.S. procedures involving comparison of the oil
with standard color tubes, or by spectrophotometric methods
(2). The authors have found the color of commercial citrus seed
oils to be in the range of from 3 to 5, by comparison with
Gardner glass color standards (2). Crude oils of good quality
are usually light or faint yellow in color, while dark oils contain
considerable quantities of free fatty acids and are of poorer
quality.
Free Fatty Acids.-High quality seed oils contain largely
triglycerides and only small quantities of free fatty acids.
Basically, free fatty acids in the oil are a result of enzymatic
hydrolysis by lipases of the glycerides to free fatty acids and
the corresponding alcohols of the glycerides. Improper handling
of the seeds prior to or during oil extraction may result in in-
creasing the free fatty acid content in the product oil, and hence,
lowering the quality. According to analyses performed in our
laboratory, good quality crude citrus seed oils have been com-
mercially produced with less than 1 % free fatty acids. Oils with
high quantities of free fatty acids will tend to smoke if used
for frying.
Rancidity.-Fats and oils can react chemically with oxygen,
resulting in a breakdown of the fatty acids (primarily un-
saturated fatty acids) to carbonyl compounds. These compounds
may change the odor and flavor of the oil, lowering the quality.
For this reason, exposure of the oil to air during processing or
storage should be kept to a minimum, especially during any heat
treatment. Quality of an oil from a rancidity standpoint may
be evaluated in several ways. These include tasting under a
variety of conditions, peroxide determination and, in some cases,
determining the quantity of an aldehyde, malonaldehyde, which
is present in oxidized fats. We have found that citrus seed oils
readily develop rancidity, and care should be taken during man-
ufacture and storage to prevent it.

Peroxide Determination.-The presence of significant quan-
tities of peroxides is somewhat indicative that an oil has re-







manufacturer produced crude oils from seeds dried in an open
flame dryer at exit stack gas temperatures of about 2500 F
(personal communication). The authors recommend exit stack
gas temperatures no higher than 2300 F, as seed kernels dried
in our pilot plant feed mill at temperatures above this value
were darkened and produced a dark brown oil of poor quality.

Color.-Color of fats and oils may be determined either by
standard A.O.C.S. procedures involving comparison of the oil
with standard color tubes, or by spectrophotometric methods
(2). The authors have found the color of commercial citrus seed
oils to be in the range of from 3 to 5, by comparison with
Gardner glass color standards (2). Crude oils of good quality
are usually light or faint yellow in color, while dark oils contain
considerable quantities of free fatty acids and are of poorer
quality.
Free Fatty Acids.-High quality seed oils contain largely
triglycerides and only small quantities of free fatty acids.
Basically, free fatty acids in the oil are a result of enzymatic
hydrolysis by lipases of the glycerides to free fatty acids and
the corresponding alcohols of the glycerides. Improper handling
of the seeds prior to or during oil extraction may result in in-
creasing the free fatty acid content in the product oil, and hence,
lowering the quality. According to analyses performed in our
laboratory, good quality crude citrus seed oils have been com-
mercially produced with less than 1 % free fatty acids. Oils with
high quantities of free fatty acids will tend to smoke if used
for frying.
Rancidity.-Fats and oils can react chemically with oxygen,
resulting in a breakdown of the fatty acids (primarily un-
saturated fatty acids) to carbonyl compounds. These compounds
may change the odor and flavor of the oil, lowering the quality.
For this reason, exposure of the oil to air during processing or
storage should be kept to a minimum, especially during any heat
treatment. Quality of an oil from a rancidity standpoint may
be evaluated in several ways. These include tasting under a
variety of conditions, peroxide determination and, in some cases,
determining the quantity of an aldehyde, malonaldehyde, which
is present in oxidized fats. We have found that citrus seed oils
readily develop rancidity, and care should be taken during man-
ufacture and storage to prevent it.

Peroxide Determination.-The presence of significant quan-
tities of peroxides is somewhat indicative that an oil has re-








ceived poor treatment or is undergoing oxidative rancidity.
Peroxide values of crude commercial citrus seed oils analyzed
in our laboratory (A.O.C.S. (2), Method Cd-8-53) have been
in the range 0.5 to 10 meq of peroxide/kg oil. However, the
method is highly empirical, and variation of results may be ob-
served due to chemical instability and changes in the peroxides
during storage of an oil.
TBA Number.-The thiobarbituric acid (TBA) test depends
on the fact that oxidized oil (possibly the malonaldehyde present
therein) produces a red color with TBA which can be estimated
colorimetrically. Theoretically, the TBA number increases with
the degree of oxidation or rancidity of a fat. Tests on commer-
cial citrus seed oil showed TBA numbers of about 2 mg malonal-
dehyde/kg oil. Procedures used for the analysis were those
described by Yu and Sinnhuber (55), with the modification that
sample sizes of 1 gm oil were used in place of fish meal.
Antioxidants-To prevent oxidation of oils during process-
ing and storage, it may be necessary to add antioxidants. This
is especially important for edible oils which may be stored for
some time during marketing and distribution. Common anti-
oxidants used or present naturally in oils include such synthetic
antioxidants as butylated-hydroxyanisole (BHA), butylated-
hydroxytoluene (BHT) and propyl gallate (PG), and the nat-
urally occurring tocopherols, respectively.
Synthetic antioxidants may be used, by approval of FDA, at
levels of 0.02% of oil for one primary antioxidant (such as
BHA, BHT, or PG), or for all combinations. BHA can survive
heat treatment and may be added to oils prior to processing.
BHT is superior to BHA (and less expensive) in oils, but does
not carry through heat treatments as well. PG is used to protect
oils during storage and will not survive heat treatments. There
are many synergistic effects when these antioxidants are used
in combination, and the best combinations depend on the use
and treatment the oil will receive.
Data from our laboratory show that citrus seed oils contain
the naturally occurring antioxidants belonging in the tocopherol
family, of which alpha-tocopherol is the predominant member.
Our results show the following contents of tocopherols in fresh
citrus seed oils (mg tocopherol/100 gm oil): alpha-tocopherol
(20 to 40 mg), beta-tocopherol (1-4 mg), gamma-tocopherol
(1 to 6 mg), delta-tocopherol (4 to 10 mg) and alpha and beta-
tocotrienol (0.15 to 1 mg). These figures are comparable to
tocopherol contents of other seed oils, and undoubtedly con-
tribute favorably to citrus seed oil stability.








ceived poor treatment or is undergoing oxidative rancidity.
Peroxide values of crude commercial citrus seed oils analyzed
in our laboratory (A.O.C.S. (2), Method Cd-8-53) have been
in the range 0.5 to 10 meq of peroxide/kg oil. However, the
method is highly empirical, and variation of results may be ob-
served due to chemical instability and changes in the peroxides
during storage of an oil.
TBA Number.-The thiobarbituric acid (TBA) test depends
on the fact that oxidized oil (possibly the malonaldehyde present
therein) produces a red color with TBA which can be estimated
colorimetrically. Theoretically, the TBA number increases with
the degree of oxidation or rancidity of a fat. Tests on commer-
cial citrus seed oil showed TBA numbers of about 2 mg malonal-
dehyde/kg oil. Procedures used for the analysis were those
described by Yu and Sinnhuber (55), with the modification that
sample sizes of 1 gm oil were used in place of fish meal.
Antioxidants-To prevent oxidation of oils during process-
ing and storage, it may be necessary to add antioxidants. This
is especially important for edible oils which may be stored for
some time during marketing and distribution. Common anti-
oxidants used or present naturally in oils include such synthetic
antioxidants as butylated-hydroxyanisole (BHA), butylated-
hydroxytoluene (BHT) and propyl gallate (PG), and the nat-
urally occurring tocopherols, respectively.
Synthetic antioxidants may be used, by approval of FDA, at
levels of 0.02% of oil for one primary antioxidant (such as
BHA, BHT, or PG), or for all combinations. BHA can survive
heat treatment and may be added to oils prior to processing.
BHT is superior to BHA (and less expensive) in oils, but does
not carry through heat treatments as well. PG is used to protect
oils during storage and will not survive heat treatments. There
are many synergistic effects when these antioxidants are used
in combination, and the best combinations depend on the use
and treatment the oil will receive.
Data from our laboratory show that citrus seed oils contain
the naturally occurring antioxidants belonging in the tocopherol
family, of which alpha-tocopherol is the predominant member.
Our results show the following contents of tocopherols in fresh
citrus seed oils (mg tocopherol/100 gm oil): alpha-tocopherol
(20 to 40 mg), beta-tocopherol (1-4 mg), gamma-tocopherol
(1 to 6 mg), delta-tocopherol (4 to 10 mg) and alpha and beta-
tocotrienol (0.15 to 1 mg). These figures are comparable to
tocopherol contents of other seed oils, and undoubtedly con-
tribute favorably to citrus seed oil stability.








Pro-oxidants.-Some materials contribute to increased oxi-
dative deterioration of fats and oils. Of these, metals which
may contaminate the oil during processing operations are of
primary importance. Reaction conditions leading to metal cat-
alysis of oxidation in oils are complex, but certain metals-
copper, iron, cobalt, manganese, nickel, and others possessing two
or more valence states with a suitable oxidation reduction po-
tential between them-can most efficiently increase the oxidative
deterioration of oils. Contact of oils with these metals should
be minimized during processing and handling.

Smoke, Flash, and Fire Points.-The smoke point is the tem-
perature at which an oil gives off a thin stream of smoke; the
flash point is the temperature at which mixtures of vapor with
air will ignite; and the fire point is the temperature at which
the oil will sustain combustion. These properties of an oil are
useful in evaluating those which might be used for frying. The
smoke point of crude citrus seed oil is about 4300 F and is in
the range of those for corn and soybean oil (4500 F). Flash
and fire points of citrus seed oil are not known.

NUTRITIONAL ASPECTS
Both man and animals may receive nutritional benefits from
the consumption of citrus seeds and products (7). Whole seeds
dried with the peel, pulp, and rag fractions of the fruit currently
are used as cattle feed, or the seeds could be separated and
processed into oil leaving a proteinaceous, oil-free meal which
might be added to feed or used for other purposes.
Seed Oil.-From the standpoint of human nutrition, a major
benefit to be derived from the consumption of citrus seed oils
(and many other seed oils) in preference to animal fats is their
high content of the essential fatty acids, linoleic and linolenic
acids. The linoleic acid content of citrus seed oils is from 30%
to 40% of the fatty acids present, and certainly makes this oil
one of those high in polyunsaturated fatty acids.
Also present in the oil are significant quantities of vitamin
E, or tocopherols. The authors have found the total quantity of
this vitamin (all tocopherols) in the oil to be in the range of
from 30 to 60 mg/100 gm oil. While the human requirement of
vitamin E is not known, daily intake in the average American
diet has been calculated as about 30 mg of mixed tocopherols.
An adult would have to consume about 4 fluid ounces of citrus
seed oil daily for a 30 mg intake of tocopherol.








Pro-oxidants.-Some materials contribute to increased oxi-
dative deterioration of fats and oils. Of these, metals which
may contaminate the oil during processing operations are of
primary importance. Reaction conditions leading to metal cat-
alysis of oxidation in oils are complex, but certain metals-
copper, iron, cobalt, manganese, nickel, and others possessing two
or more valence states with a suitable oxidation reduction po-
tential between them-can most efficiently increase the oxidative
deterioration of oils. Contact of oils with these metals should
be minimized during processing and handling.

Smoke, Flash, and Fire Points.-The smoke point is the tem-
perature at which an oil gives off a thin stream of smoke; the
flash point is the temperature at which mixtures of vapor with
air will ignite; and the fire point is the temperature at which
the oil will sustain combustion. These properties of an oil are
useful in evaluating those which might be used for frying. The
smoke point of crude citrus seed oil is about 4300 F and is in
the range of those for corn and soybean oil (4500 F). Flash
and fire points of citrus seed oil are not known.

NUTRITIONAL ASPECTS
Both man and animals may receive nutritional benefits from
the consumption of citrus seeds and products (7). Whole seeds
dried with the peel, pulp, and rag fractions of the fruit currently
are used as cattle feed, or the seeds could be separated and
processed into oil leaving a proteinaceous, oil-free meal which
might be added to feed or used for other purposes.
Seed Oil.-From the standpoint of human nutrition, a major
benefit to be derived from the consumption of citrus seed oils
(and many other seed oils) in preference to animal fats is their
high content of the essential fatty acids, linoleic and linolenic
acids. The linoleic acid content of citrus seed oils is from 30%
to 40% of the fatty acids present, and certainly makes this oil
one of those high in polyunsaturated fatty acids.
Also present in the oil are significant quantities of vitamin
E, or tocopherols. The authors have found the total quantity of
this vitamin (all tocopherols) in the oil to be in the range of
from 30 to 60 mg/100 gm oil. While the human requirement of
vitamin E is not known, daily intake in the average American
diet has been calculated as about 30 mg of mixed tocopherols.
An adult would have to consume about 4 fluid ounces of citrus
seed oil daily for a 30 mg intake of tocopherol.








Pro-oxidants.-Some materials contribute to increased oxi-
dative deterioration of fats and oils. Of these, metals which
may contaminate the oil during processing operations are of
primary importance. Reaction conditions leading to metal cat-
alysis of oxidation in oils are complex, but certain metals-
copper, iron, cobalt, manganese, nickel, and others possessing two
or more valence states with a suitable oxidation reduction po-
tential between them-can most efficiently increase the oxidative
deterioration of oils. Contact of oils with these metals should
be minimized during processing and handling.

Smoke, Flash, and Fire Points.-The smoke point is the tem-
perature at which an oil gives off a thin stream of smoke; the
flash point is the temperature at which mixtures of vapor with
air will ignite; and the fire point is the temperature at which
the oil will sustain combustion. These properties of an oil are
useful in evaluating those which might be used for frying. The
smoke point of crude citrus seed oil is about 4300 F and is in
the range of those for corn and soybean oil (4500 F). Flash
and fire points of citrus seed oil are not known.

NUTRITIONAL ASPECTS
Both man and animals may receive nutritional benefits from
the consumption of citrus seeds and products (7). Whole seeds
dried with the peel, pulp, and rag fractions of the fruit currently
are used as cattle feed, or the seeds could be separated and
processed into oil leaving a proteinaceous, oil-free meal which
might be added to feed or used for other purposes.
Seed Oil.-From the standpoint of human nutrition, a major
benefit to be derived from the consumption of citrus seed oils
(and many other seed oils) in preference to animal fats is their
high content of the essential fatty acids, linoleic and linolenic
acids. The linoleic acid content of citrus seed oils is from 30%
to 40% of the fatty acids present, and certainly makes this oil
one of those high in polyunsaturated fatty acids.
Also present in the oil are significant quantities of vitamin
E, or tocopherols. The authors have found the total quantity of
this vitamin (all tocopherols) in the oil to be in the range of
from 30 to 60 mg/100 gm oil. While the human requirement of
vitamin E is not known, daily intake in the average American
diet has been calculated as about 30 mg of mixed tocopherols.
An adult would have to consume about 4 fluid ounces of citrus
seed oil daily for a 30 mg intake of tocopherol.








Seed Meal.-The dry, oil-free meal obtained during the oil
manufacturing operation has a high protein content. The com-
position of the press cake meal obtained in the preparation of
grapefruit seed oil is presented in Table 6. In addition, Am-
merman et al. (3) found 16.2% protein in the whole seeds,
19.5% in the kernels, and 6.1% in the hulls. When fed to lambs
as 88% of the total protein in the ration, the protein of citrus
seed meal was equal in digestibility and biological value to the
protein of soybean meal.
A toxic factor has been reported in commercial citrus seed
meal (14). When fed as 20% of the diet of white Leghorn
chicks, this factor resulted in high mortality and unsatisfactory
growth. Chemical analysis and alcohol solubility suggested that
the factor was limonin, a bitter principle found in the seed. To
the authors' knowledge, toxicity of citrus seeds, oil, or meal to
animals other than chickens has not been reported.
The amino acid composition of the meal has been determined
in our laboratory and is listed in Table 7. When values for five
amino acids important in livestock feeding and animal nutrition
are compared with soybean, the following ratios of the amino
acids in orange seed to soybean are obtained: glycine 1.2, cystine
1.3, methionine 1.4, lysine 0.45, and tryptophan 1.6. For live-
stock feeding, the quantities of glycine, cystine, methionine, and
tryptophan in citrus seed meal would be an important plus.
Similarly, the lower amount of lysine would be a deterrent.
The data in Table 7 indicate some differences when compar-
ing the amino acid composition of orange and grapefruit seed
meals. Notably, the amounts of cystine and methionine were
approximately 1.5 times higher in the grapefruit than in the
orange seed meal, but orange seed meal had about 1.6 times
more tryptophan than grapefruit. The values for total sulfur


Table 6. Percentage Composition of Grapefruit Seed Press Cake.*

Moisture 3.4 (%) SiO, 0.08 (%)
Ash 4.0 S 0.09
N as NHa 4.2 Ca 0.35
N as Protein 21.6 Mg (MgO) 0.39
Crude Fat 14.0 NaCI + KCI 2.48
Crude Fiber 26.5 Phosphates 0.55
Fe 0.001
*Table from reference (37).








Table 7. Amino Acids of Citrus Seed Meal and Soybeans.


mg Amino Acid/g Nitrogen in Product
Amino Acid Orange Grapefruit Soybean*

Aspartic Acid 548 560 731
Threonine 186 181 241
Serine 239 290 320
Glutamic Acid 1594 1623 1169
Proline 256 253 343
Glycine 322 272 261
Alanine 231 230 266
Cystine 110 174 83
Valine 307 333 300
Methionine 112 165 79
Isoleucine 219 224 284
Leucine 394 446 486
Tyrosine 168 166 196
Phenylalanine 306 296 309
Lysine 178 175 399
Histidine 128 108 158
Arginine 695 596 452
Ammonia -
Tryptophan 125 79 80

*Amino acid values for soybean from reference 49.

amino acids of citrus seed meal are higher than for protein
from many common seeds, nuts, and grains (49).
There is concern that removal of seeds from citrus pulp
would lower the protein content of cattle feed to the point of
not passing the guaranteed protein analysis (6%). This is un-
true, and data is presented in Table 8 showing that removal of
all seeds from commercial Valencia pulp would lower the protein
content by only 0.4%. It can be further stated that the meal
may still be added back to the dried pulp after oil extraction, a
common practice in the manufacture of soy and cottonseed oils.
A similar argument could be presented related to the concern
that removal of the seeds from dried pulp would lower the fat
content sufficiently to cause failure of a feed to pass the guaran-
teed minimum fat analysis. It can be shown that 65% of the
fat in dried citrus pulp is derived from sources other than seeds,








and that removal of seeds from Valencia pulp would cause the
fat content of the dried pulp to be reduced only about 1.1%.
Data from the 1971 report of the Florida Department of
Agriculture for 278 samples of feed analyzed showed fat con-
tents in the range of from 1.1% to 7.3%, with an average value
for all varieties of dried citrus pulp of 3.7% fat. Most manu-
facturers guarantee 2% to 3% fat in their dried citrus pulp,
and the pulp is allowed by law to be 0.5 % below its tag reading
before subject to penalty. Hence, even with the 1.1% reduction
caused by removal of seeds from the pulp, the average fat con-
tent would still be above the 2% to 3% declared on most labels.
The above arguments relate to the fat and protein contents
of dried pulp from Valencia oranges. The authors agree that
the percentages of fat and protein attributed to seeds in the
pulp will be higher for the more seedy varieties. Complete re-
moval of all seeds from the pulp of these seedy varieties may
cause the fat or protein content to be lower than the guaranteed
analysis. However, the most efficient commercial process for
seed recovery from pulp can obtain only 60% to 80% of the
seeds present, leaving sufficient seeds so that the pulp can meet
the guaranteed analysis for fat and protein.


Table 8. Protein Yield Data for Seeds in Valencia Citrus Pulp.
Material Amount
Fruit yields to wet pulp (boxes/ton) 50
Seeds in fruit (Ibs/box) 0.7
Wet seeds in wet pulp (Ibs/ton) 35
Wet seeds in dry pulp (Ibs/ton) 157.5
Dry seeds in dry pulp (Ibs/ton) 52.5
Oil content of seeds (%) 40
Oil in dry pulp (Ibs/ton) 21
Meal in dry pulp (Ibs/ton) 31.5
Protein content of meal (%) 25
Protein in dry pulp (Ibs/ton) 7.9
Guaranteed protein analysis of citrus pulp (%)* 6
Guaranteed protein analysis of citrus pulp (Ibs/ton) 120
Protein content of seedless pulp (%) 5.6
Protein loss by seed removal from pulp (%) 0.4

*Florida Commercial Feed Law (paragraph 580.131) allows citrus pulp to be
1% below its tag reading before subject to penalty.








Table 9 lists the authors' data concerning seed removal from
dried citrus pulp of four different varieties of fruit. By exam-
ination of this table, it can be seen that the protein content of
dried pulp is not seriously affected by seed removal. However,
the fat content of pineapple oranges and seedy grapefruit would
be lowered to less than 1.5% if 100% of the seeds were removed
from pulp of these varieties.

Table 9. Protein and Fat Contents of Dried Citrus Pulp (8% Moisture)
Before and After Seed Removal.

Protein % Fat %
Seeds Seeds Seeds Seeds
Variety Present Removed Present Removed

Valencia orange 6.5 6.3 2.3 1.5
Pineapple orange 6.7 5.8 5.1 1.3
Seedy grapefruit 7.6 6.7 5.1 1.2
Marsh grapefruit 7.3 7.1 1.3 0.7


UTILIZATION
Refined citrus seed oil is bland and pale yellow in color and
with proper processing could be utilized in much the same way
as the oil of other seeds, such as soybeans and cottonseeds. The
refined oil may be used as a salad or cooking oil, but would need
partial hydrogenation for suitable shelf life, primarily because
of its linolenic acid content. With hydrogenation, the oil could
also be manufactured into margarines (5) and shortenings.
If production of a line of specialty fat products made from
citrus were to be a reality, such items as mayonnaise and salad
dressings should be popular. For mayonnaise production, re-
fined seed oil which had not been bleached would be desired,
since the yellow color of the oil would give the desired color in
the finished product.
Utilization of the oil and defatted meal flour as a beverage
clouding agent has been proposed (31), and a patent has been
issued. As previously mentioned, the defatted meal and hulls
from the oil processing operation may also be added back to the
pulp. Table 10 shows the estimated annual yield of dried Florida
citrus seed by-products, including crude oil, meal, and hulls. This
data was calculated on the basis of the actual number of boxes
of each variety processed during the 1970-71 season (151.6 mil-
lion boxes total), and represents the potential yield of seed oil,








meal, and hulls only if all available seeds were processed for
these products. Table 10 shows potential yields of 28, 39, and
21 million pounds of seed oil, meal and hulls, respectively.
Utilization of citrus seed oils has been evaluated (23), and
some unusual applications have been proposed. Kaplan (29)
patented the use of grapefruit seed oil as a lubricant and pre-
servative to treat textile fibers such as silk, wool and rayon;
Stambovsky (44) discusses utilization of citrus seed oil as a
food, in paints, and for soaps.


Table 10. Estimated Annual Yield of Dried Florida Citrus Seed By-Products.

Millions of Lbs

Oil Meal Hulls

Oranges
Early and Midseason 18.6 25.6 14.0
Valencia 4.4 6.2 3.4
Temple 0.6 0.8 0.4

Grapefruit
Duncan 3.8 5.2 2.8
Marsh 0.4 0.4 0.4
Pink 0.2 0.2 0.2

Other
Tangerines 0.1 0.2 0.1
Tangelos 0.1 0.2 0.1












LITERATURE CITED


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This public document was promulgated at an annual cost
of $1968.27 or a cost of 24.6 cents per copy to consolidate
scientific information on citrus seed oils, assist the citrus
industry with utilization and processing of these oils, and
inform the food industry of their potential uses.

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B6/22/99 34772 V g




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