• TABLE OF CONTENTS
HIDE
 Title Page
 Credits
 Table of Contents
 Introduction
 Review of literature
 Methods of commercial manufact...
 Experimental procedure
 Experimental results
 Discussion of results
 Summary
 Acknowledgments and literature...
 Historic note






Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 452
Title: Florida citrus oils
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027437/00001
 Material Information
Title: Florida citrus oils commercial production methods and properties of essential oils (1947-48 season)
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 44 p. : ill. ; 23 cm.
Language: English
Creator: Kesterson, J. W
McDuff, O. R
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1948
 Subjects
Subject: Citrus oils   ( lcsh )
Citrus fruits -- By-products -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 42-44.
Statement of Responsibility: J.W. Kesterson and O.R. McDuff.
General Note: Cover title.
General Note: "Cooperative project-Citrus Experiment Station and Florida Citrus Commission"--T.p.
 Record Information
Bibliographic ID: UF00027437
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000925533
oclc - 18270729
notis - AEN6186

Table of Contents
    Title Page
        Page 1
    Credits
        Page 2
        Page 3
    Table of Contents
        Page 4
    Introduction
        Page 5
    Review of literature
        Page 6
        Page 7
        Page 8
    Methods of commercial manufacture
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
    Experimental procedure
        Page 17
        Page 18
        Page 19
    Experimental results
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
    Discussion of results
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
    Summary
        Page 39
        Page 40
        Page 41
    Acknowledgments and literature cited
        Page 42
        Page 43
        Page 44
    Historic note
        Page 45
Full Text



November, 1948


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
HAROLD MOWRY, Director
GAINESVILLE, FLORIDA








FLORIDA CITRUS OILS
Commercial Production Methods and Properties
of Essential Oils
(1947 48 Season)

J. W. KESTERSON and 0. R. McDUFF










TECHNICAL BULLETIN











Cooperative Project -Citrus Experiment Station and
Florida Citrus Commission

Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


Bulletin 452










BOARD OF CONTROL

J. Thos. Gurney, Chairman, Orlando
N. B. Jordan, Quincy
Thos. W. Bryant, Lakeland
J. Henson Markham, Jacksonville
Hollis Rinehart, Miami
W. F. Powers, Secretary. Tallahassee


EXECUTIVE STAFF

J. Hillis Miller, Ph.D., President of the
University3
H. Harold Hume, D.Sc., Provost for Agr.s
Harold Mowry, M.S.A., Director
L. O. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield, M.S., Asst. Dir., Admin.
J. Francis Cooper, M.S.A., Editor3
Clyde Beale, A.B.J., Associate Editors
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Manager3
Geo. F. Baurhman, M.A., Business Managers
Claranelle Alderman, Accountant3


MAIN STATION, GAINESVILLE

AGRICULTURAL ENGINEERING
Frazier Rogers, M.S.A., Agr. Engineers
J. M. Johnson, B.S.A.E., Asso. Agr. Engineers
J. M. Myers, B.S., Asso. Agr. Engineer
R. E. Choate. B.S.A.E., Asst. Agr. Engineers
A. M. Pettis, B.S.A.E., Asst. Agr. Engineer2

AGRONOMY

Fred H. Hull, Ph.D., Agronomist'
G. E. Ritchey, M.S., Agronomist2
G. B. Killinger, Ph.D., Agronomists
H. C. Harris, Ph.D., Agronomist3
R. W. Bledsoe, Ph.D., Agronomist
M. E. Paddick, Ph.D., Agronomist
S. C. Litzenberger, Ph.D.,' Associate
W. A. Carver, Ph.D., Associate
Fred A. Clark, B.S., Assistant

ANIMAL INDUSTRY

A. L. Shealy, D.V.M., An. Industrialists
R. B. Becker, Ph.D., Dairy Husbandman3
E. L. Fouts, Ph.D., Dairy Technologist3
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M. Veterinarian3
L. E. Swanson, D.V.M., Parasitologist
N. R. Mehrhof, M.Agr., Poultry Husb.3
G. K. Davis, Ph.D., Animal Nutritionist3
R. S. Glasseock, Ph.D., An. Husbandman3
P. T. Dix Arnold, M.S.A., Asst. Dairy Husb.3
L. E. Mull, M.S., Asst. in Dairy Tech.
Katherine Boney, B.S., Asst. Chem.
J. C. Driggers, B.S.A., Asst. Poultry Husb.3
Glenn Van Ness, D.V.M., Asso. Poultry
Pathologist
S. John Folks, B.S.A., Asst. An. Husb.3
W. A. Krienke, M.S., Asso. in Dairy Mfs.S
S. P. Marshall, Ph.D., Asso. Dairy Husb.3
C. F. Simpson, D.V.M., Asso. Veterinarian
C. F. Winchester, Ph.D., Asso. Biochemist3


ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agri. Economist'
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Associate
D. E. Allez'er, M.S., Associate
D. L. Brooke, M.S.A., Associate
R. E. L. Greene, Ph.D., Agri. Economist
H. W. Little, M.S., Assistant

Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist
J. C. Townsend, Jr., B.S.A., Agr. Statisticians
J. B. Owens, B.S.A., Agr. Statistician2
J. F. Steffens, Jr., B.S.A., Agr. Statistician2

ECONOMICS, HOME
Ouida D. Abbott, Ph.D., Home Econ.1
R. B. French, Ph.D., Biochemist

ENTOMOLOGY
A. N. Tissot, Ph.D.. Entomologist'
L. C. Kuitert, Ph.D., Assistant
H. E. Bratley, M.S.A., Assistant

HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist'
F. S. Jamison, Ph.D., Horticulturists
H. M. Reed, B.S., Chem., Veg. Processing
Byron E. Janes, Ph.D., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
R. K. Showalter, M.S., Asso. Hort.
Albert P. Lorz, Ph.D., Asso. Hort.
R. H. Sharpe, M.S., Asso. Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.
Victor F. Nettles, M.S.A., Asst. Hort.4
F. S. Lagasse, Ph.D., Asso. Hort.2
L. H. Halsey, B.S.A., Asst. Hort.
F. E. Myers, B.S.A., Asst. Hort.

PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist's
Phares Decker, Ph.D., Asso. Plant Path.
Erdman West, M.S., Mycologist and Botanist
Howard N. Miller, Ph.D., Asso. Plant Path.
Lillian E. Arnold, M.S., Asst. Botanist
SOILS
F. B. Smith, Ph.D., Microbiologist 3
.Gaylord M. Volk, Ph.D., Chemist
J. R. Henderson, M.S.A., Soil Technologists
J. R. Neller, Ph.D., Soils Chemist
Nathan Gammon, Jr., Ph.D., Soils Chemist
C. E. Bell, Ph.D., Associate Chemist
R. A. Carrigan, Ph.D., Asso. Biochemists
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, Ph.D., Asso. Microbiologists
R. E. Caldwell, M.S.A., Asst. Chemists
J. B. Cromartie, B.S.A., Soil Surveyor
Ralph G. Leighty, B.S., Asso. Soil Surveyor
V. W. Cyzycki, B.S., Asst. Soil Surveyor
R. B. Forbes, M.S., Asst. Soils Chemist
W. L. Pritchett, M.S., Asst. Chemist
Jean Beem, B.S.A., Asst. Soil Surveyor

1 Head of Department.
2In. cooperation with U. S.
3 Cooperative, other divisions, U. of F.
4 On leave.









BRANCH STATIONS

NORTH FLORIDA STATION, QUINCY
J. D. Warner, M.S., Vice-Director in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
W. H. Chapman, M.S., Asso. Agron.
R. C. Bond, M.S.A., Asso. Agronomist
L. G. Thompson, Ph.D., Soils Chemist
Frank S. Baker, Jr., B.S., Asst. An. Husb.
Kelvin Dorward, M.S., Entomologist

Mobile Unit, Monticello
R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Marianna.
R. W. Lipscomb, M.S., Associate Agronomist

Mobile Unit, Wewahitchka
J. B. White, B.S.A., Associate Agronomist

Mobile Unit, DeFuniak Springs
R. L. Smith, M.S., Associate Agronomist

CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Vice-Director in Charge
W. L. Thompson, B.S., Entomologist
J. T. Griffiths, Ph.D., Asso. Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, M.S., Plant Pathologist'
R. K. Voorhees, M.S., Asso. Horticulturist
C. R. Stearns, Jr., B.S.A., Asso. Chemist
James K. Colehour, M.S., Asst. Chemist
T. W. Young, Ph.D., Asso. Horticulturist
J. W. Sites, M.S.A., Horticulturist
H. O. Sterling, B.S., Asst. Horticulturist
J. A. Granger, B.S.A., Asst. Horticulturist
H. J. Reitz, M.S., Asso. Horticulturist
Francine Fisher, M.S., Asst. Plant Path.
I. W. Wander, Ph.D., Soils Chemist
A. E. Willson, B.S.A., Asso. Biochemist
J. W. Kesterson, M.S., Asso. Chemist
R. N. Hendrickson, B.S., Asst. Chemist
E. H. Bitcover, M.A., Soils Chemist
L. C. Knorr, Ph.D., Asso. Histologist
Joe P. Barnett, B.S.A., Asst. Horticulturist
J. C. Bowers, B.S., Asst. Chemist
D. S. Prosser, Jr., B.S., Asst. Horticulturist
R. W. Olsen, B.S., Biochemist
F. W. Wenzel, Jr., Ph.D., Supervisory Chem.

EVERGLADES STATION, BELLE GLADE
R. V. Allison, Ph.D., Vice-Director in Charge
F. D. Stevens, B.S., Sugarcane Agronomist
Thomas Bregger, Ph.D., Sugarcane
Physiologist
J. W. Randolph, M.S., Agricultural Engineer
W. T. Forsee, Jr., Ph.D., Chemist
R. W. Kidder, M.S., Asso. Animal Husb.
T. C. Erwin, Assistant Chemist
Roy A. Bair, Ph.D., Agronomist
C. C. Seale, Asso. Agronomist
N. C. Hayslip, B.S.A., Asso. Entomologist
E. H. Wolf, Ph.D., Asst. Horticulturist
W. H. Thames, M.S., Asst. Entomologist
J. C. Hoffman, M.S., Asso. Horticulturist


C. B. Savage, M.S.A., Asst. Horticulturist
D. L. Stoddard, Ph.D., Asso. Plant Path.

SUB-TROPICAL STATION, HOMESTEAD
Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
D. O. Wolfenbarger, Ph.D., Entomologist
Francis B. Lincoln, Ph.D., Horticulturist
Robt. A. Conover, Ph.D., Asso. Plant Path.
R. W. Harkness, Ph.D., Asst. Chemist
Milton Cobin, B.S., Asso. Horticulturist


W. CENT. FLA. STATION, BROOKSVILLE
William Jackson, B.S.A., Animal .Husband-
man in Charge2


RANGE CATTLE STATION, ONA
W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Associate Agronomist
D. W. Jones, B.S., Asst. Soil Technologist
H. J. Fulford, B.S.A. Asst. Animal Husb.


CENTRAL FLORIDA STATION, SANFORD
R. W. Ruprecht, Ph.D., Vice-Dir. in Charge
J. W. Wilson, Sc.D., Entomologist
Ben F. Whitner, Jr., B.S.A., Asst. Hort.


WEST FLORIDA STATION, MILTON
H. W. Lundy, B.S.A., Associate Agronomist


FIELD STATIONS

Leesburg
G. K. Parris, Ph.D., Plant Path. in Charge

Plant City
A. N. Brooks, Ph.D., Plant Pathologist

Hastings
A. H. Eddins, Ph.D., Plant Path. in Charge
E. N. McCubbin, Ph.D., Horticulturist

Monticello
A. M. Phillips, B.S., Asso. Entomologist2

Bradenton
J. R. Beckenbach, Ph.D., Hort. in Charge
E. G. Kelsheimer, Ph.D., Entomologist
David G. Kelbert, Asso. Horticulturist
E. L. Spencer, Ph.D., Soils Chemist
Robert O. Magie, Ph.D., Gladioli Hort.
J. M. Walter, Ph.D., Plant Pathologist
Donald S. Burgis, M.S.A., Asst. Hort.

Lakeland
Warren O. Johnson, B.S., Meteorologist2

SHead of Department.
2In cooperation with U. S.
3 Cooperative, other divisions, U. of F.
4 On leave.







CONTENTS
PAGE

IN TRODUCTION ............... ..................................................................... .... ... ... 5

REVIEW OF LITERATURE ............................. ......... ............----............... ...... 6

METHODS OF COMMERCIAL MANUFACTURE ................................. ............ ... 9

Coldpressed Oils ............--.....-- ..-- ....---..... -. ---................... 9

Distilled Oils ..... ---.......... ---------------..... ............. -....--....---.. .....---- .......-.. 14

EXPERIMENTAL PROCEDURE ............. ........----..............-- .......-- .....-- 17

Survey of Commercial Plants ..--...-... .................... ..-.. .............. .. 17

Collection of Samples .-......- ---.---............---..... ... ........--- 18

Methods of Analyses ....................---.-------................... 19

EXPERIMENTAL RESULTS ...............---------- ----....................... 20

Coldpressed Oil of Orange ............... ......................................... 20

Coldpressed and Distilled Oils of Orange, Grapefruit, Tangerine
and Lime .......... ..... ...........-........... ----------. ...........-........... 28

DISCUSSION OF RESULTS ...........-------....- --..............- .................. ...... 32

Relation of Yield to Properties and U. S. P. Specifications .................. 32

Effect of Aqueous Phase on Aldehyde Content --.................---................ 36

Relation of Fruit Variety to Properties ...............----- ..... ...-...----.... 37

Storage of Fruit Prior to Oil Extraction .....-............. .................... 38

Effect of Maturity on Properties --..................-..... ....-. .......- ...- 38

Comparison of Coldpressed and Distilled Oils ............-...........-............. 38

Comparison of Floridian Essential Oils with Oils from Other Sources 39

SUM M ARY .......................................................... ................................. ......... 39

ACKNOWLEDGMENTS .................................... .. .........----- -- 42

LITERATURE CITED .................................................................. ........ ............... 42









FLORIDA CITRUS OILS
Commercial Production Methods and Properties
of Essential Oils
(1947- 48 Season)
J. W. KESTERSON 1 and O. R. McDUFF 2

INTRODUCTION
Today the processing of citrus fruits is a vast business in
Florida, almost 50 million boxes of oranges, grapefruit, and tange-
rines having been processed commercially during the 1947-48
season. This represented approximately 55 percent of the citrus
crop which was harvested. The principal and primary products
which resulted from the processing of this huge quantity of
fruit were canned unconcentrated and concentrated citrus juices
and canned citrus sections.
Over half of the weight of the 50 million boxes of citrus fruits
used by the processing industries consisted of peel, pulp, rag,
and seeds. During the past 15 years an entirely new industry
has developed to utilize these enormous quantities of refuse from
the canneries, formerly considered waste products but now
fundamental in the economy of Florida.
The essential oil, found in the peel of the fruit, is the first
product recovered from cannery refuse. Oil of orange is the
most useful of the citrus oils produced in Florida, and commands
a price which justifies economically the operation of a plant for
its recovery.
A one-year survey of the commercial production of essential
oils in Florida was completed in June 1948, near the end of
another citrus processing season. Methods of commercial pro-
duction used throughout the state during the 1947-48 season
were studied and physical and chemical properties of many
types of essential oils were determined. The principal purpose
of this investigation was to determine by what means essential
oils of very high quality could be produced. Through the use
of the data obtained, it is hoped that the citrus industry in
Florida will be able to produce citrus oils which will consistently
meet the specifications of the United States Pharmacopoeia

1Associate Chemist, Citrus Experiment Station, Lake Alfred, Florida.
SResearch Fellow, Florida Citrus Commission, Citrus Experiment Station,
Lake Alfred, Florida.






Florida Agricultural Experiment Station


(24)3 and also other high quality requirements of essential oil
consumers throughout the country. Production of oils of high-
est quality and uniformity should result in a larger consumer
market. Another purpose of this study was to determine the
relationship between the physical and chemical characteristics
of the various types of oils and such factors as methods of
extraction, methods of processing, fruit variety, fruit maturity,
and others.
It is realized that the results herein presented are based on
the commercial production of essential oils for only one season.
However, representatives of the citrus industry have cooperated
readily and have shown keen interest in this work. Results of
this investigation are presented now in the belief that they will
be of immediate help to manufacturers now producing essential
oils in Florida. A similar survey will be continued for one or
two more seasons, and other factors affecting quality, such as
stability and flavor, will be investigated.

REVIEW OF LITERATURE
Many investigators have pointed out that the quality of citrus
oils is dependent upon many factors, some of which are soil,
climate, method of extraction of the oil, weather, and maturity
of the fruit.
Citrus oils are contained in oval, balloon-shaped oil sacs or
vesicles located in the outer rind or flavedo of the fruit. Winton
and Winton (26) describe the exact location of these oil sacs
in their discussion of the microscopic structure of the flavedo
of the orange. Hood (15) found a wide variation in the oil yield
of Florida oranges, reporting values of 0.11 to 0.58 percent
calculated on the weight of the whole fruit. He stated that the
oil content does not reach its maximum until the oranges are
fully mature, but is present in commercial quantities before the
fruit is ready for harvest. He also noted that a decrease in oil
content immediately follows a period of rainfall. Bartholomew
and Sinclair (3) studied the effect of age, size, and environment
on the relative amounts of oil in California oranges. Atkins,
Wiederhold, and Heid (2) reported the oil content of cull Persian
limes to be 0.32 percent on a whole fruit basis.
To secure the oil from the peel of citrus fruits, the oil sacs
must be punctured by either pressure or rasping. Methods of

SItalic figures in parentheses refer to Literature Cited in the back of
this bulletin.







Florida Citrus Oils


oil extraction used in Florida during the 1937-38 season were
investigated by von Loesecke and Pulley (25) and they showed
that the method of preparation had an effect upon the physical
characteristics of the oil. However, they did not find any rela-
tion between the time of production and the physical character-
istics, and reported that there were no great differences in the
properties of the oil from different fruit varieties or from fruit
produced in different counties. Atkins, Wiederhold, and Heid
(2) extracted oil from cull limes by using both a screw and a
Pipkin (22) press and the centrifuging of lime oil emulsions has
been discussed by Moore, Atkins, and Wiederhold (17). Guenther
(13) in a recent series of articles is reviewing methods of oil
extraction used in the United States and in foreign countries, and
states that the method of oil extraction and the amount of
carrier water used in a process affect the quality of the oil.
The physical and chemical characteristics of Florida orange,
grapefruit, tangerine, and lime oils have been reported by many
investigators (2, 5, 9, 11, 14, 18, 19, and 25). Some of these
results reported are presented in Table 1, which also includes
values for oils from other sources as reported by Poore (23)
and Guenther (7, 9). Foote and Gelpi (5) noted variations
in the properties of different lots of Floridian oil of orange and
suggested that producers should unite in the blending and mar-
keting of their oils in an effort to maintain the same quality
from year to year.
Nelson (18), Nelson and Mottern (19, 20), and Markley,
Nelson, and Sherman (16) have carried out investigations rela-
tive to the chemical constituents of orange, grapefruit, and
tangerine oils produced in Florida.
Guenther (8) stated that Naves reported that Guinea orange
oils extracted from fully matured fruit showed a higher specific
gravity, refractive index, aldehyde content, and evaporation resi-
due but a lower optical rotation than oils pressed from green fruit.
When oranges were kept in cold storage for periods longer
than six weeks previous to the extraction of the oil, de Villiers
(4) found an increase in the specific gravity, optical rotation,
iodine number, and saponification value, but a decrease in the
aldehyde content of the oil.
Fundamental information relative to all types of essential
oils produced throughout the world is found in Perry (21) and
Gildemeister and Hoffman (6). Guenther (12) has written the
first of a series of volumes in which he is bringing the whole






TABLE 1.-PROPERTIES OF CITRUS OILS AS REPORTED BY OTHER INVESTIGATORS.
Florida California
Coldpressed Coldpressed Coldpressed Other Florida Distilled Oils
Orange Orange Orange Coldpressed Oils_
Cali-
U.S.P. XIII Source 1 Source 2 Valencia Navel Grapefruit Tange- Lime fornia Florida
Specifications ____ ___ rine __ Orange Lime
Reference (24) (25) (5) (23) (23) (19) (11) (9) (7) (9)

Specific 0.842 0.840
gravity to 0.8434 0.8425 0.8440 0.8455 0.8563 0.845 0.886 to 0.8632
(25C./25"C.) 0.846 (20C./20C.) (15C.) 0.842 (15C.)


Refractive 1.4723 1.4717
index to 1.4726 1.4734 1.4735 1.4738 1.4758 1.4748 1.4855 to 1.4759
(20C.) 1.4737 1.4730

Evaporation not less
residue than 4.18 2.80 3.61 4.53 7 to 8 3.3 13.0 0.5 to 1
% 1.7%


Optical not less than +98
rotation +94 and not +96.49 +95.5 +97.78 +96.93 +93.280 +92.50 +41.26 to +43.200
(25"C.) more than +990 (20C.) (20C.) (20C.) +99.1
in 100 mm tube

Optical equal to original
rotation oil or not more +97.55* +97.50 +99.21" +98.71*
- (25C.) than 20 (20C.) (200C.)
- difference
not less than
Refractive 0.0008 and not
S index more than 0.0015 1.4719 1.4729 1.4723 1.4724
(20C.) lower than
_________ original oil _






Florida Citrus Oils


subject up-to-date. In this first volume he ably presents in-
formation on the production, chemistry, analysis, and uses of
the essential oils.
In spite of the profusion of literature there has been lacking
sufficient knowledge concerning the character of oils produced
in Florida. Such information must necessarily represent broad
scale sampling to include the effects of varieties, season, and
methods of extraction if an accurate picture of the production
is to be presented. In this work the writers have attempted to
produce such an accurate broad scale picture that covers the
entire production in Florida, and all sampling has been carried
out accordingly.

METHODS OF COMMERCIAL MANUFACTURE
COLDPRESSED OILS
General Processing Procedure.-Citrus peel oils are expressed
in Florida by four different types of equipment; namely, (1)
Pipkin roll, (2) screw press, (3) Fraser Brace extractor, and
(4) Pipkin juice extractor. The general processing procedure,
used after the extraction of oil from the peel, is very similar
in most of the commercial plants. All of the above methods
of extraction give an emulsion of oil and water. The oil is
separated centrifugally from the aqueous phase by passing the
emulsion through a sludger (8,000-10,000 r.p.m.) and then
through a polisher (16,000-18,000 r.p.m.). Following separation,
the oil is stored for approximately one week at 32o-400 F. and
during this winterizing treatment undesirable waxy materials
separate from the oil and are allowed to settle. The clear oil
is decanted into stainless steel storage tanks or tin-dipped con-
tainers, which are then maintained at a storage temperature of
about 400 F. Air is usually excluded from the container in
order to prevent deterioration. Exclusion of air usually is ac-
complished either by filling the container full of oil or by dis-
placement of the air with carbon dioxide.
Pipkin Roll Method of Extraction.-A Pipkin Roll (22) is
shown in Fig. 1, and the flow and material balance sheet for this
process is given in Fig. 2. In this method the oil is expressed
by passing peel of the fruit between two striated rollers of
stainless steel that turn in opposite directions. The distance
between the two rollers is adjusted so that the pressure against
the peel is just sufficient to puncture the oil cells without break-
ing or rasping the peel. Small striations or grooves are dis-






Florida Agricultural Experiment Station


Fig. 1.-Pipkin roll. (Photograph courtesy Essential Oil Producers, Inc.,
Dunedin, Fla.)
tribute over the entire surface of the rolls and are of a depth
sufficient to receive the oil from the oil cells, thereby keeping
it out of contact with the peel and thus eliminating to some ex-
tent its absorption by the albedo of the fruit.
Screw Press Method of Extraction.-In this method tapered
screws press the crushed peel against a perforated screen, there-
by squeezing out the oil. This operation can be carried out with










Florida Citrus Oils 11


the screws in either a vertical or horizontal position. Water

may, or may not, be used in the pressing operation. Figure 3

is a flow and material balance sheet for the manufacture of

coldpressed citrus peel oil by the use of screw presses.







CITRUS PEEL
FROM
JUICE PLANT
22.5 TON/HR.


PIPKIN ROLL PIPKIN ROLL PIPKIN ROLL PIPKIN ROLL
5.6 TON/HR 5.6 TON/HR. I .6 TON/HR. 5.6 TON/HR.


PRESS EFFLUENT PRESS EFFLUENT PRESS EFFLUENT PRESS EFFLUENT
32 GAL./HR. 32 GAL./HR. 32 GAL./HR. 32 GAL./HR.




STORAGE STORAGE
TANK TANK

80 GAL. O8 GAL.






I SLUDER I SLUDGE
128 GAL./HR. EFFLUENT


SLUDGE TO
















PIPKIN ROLL. r
FLOW AND MATERIAL BAL E SEWER
122

POLISHER EFFLUENT
SHARPLES -- 1 FROM
18000 R.RM. POLISHER



PEEL 01L
COLD PRESSED
6 GAL./HR.





PIPKIN ROLL
FLOW AND MATERIAL BALANCE SHEET
COLD PRESSED CITRUS PEEL OIL MANUFACTURE

AQUEOUS PHASE 21.5 GAL./GAL. OIL
YIELD 1.85 LB. OIL/TON PEEL
VARIETY LATE SEASON ORANGES

APR.L I, I041 JAMES W. =TERON
Fig. 2.-Flow. and material balance sheet for process using Pipkin roll.


Fig. 2.--Flow and material balance sheet for process using Pipkin roll.










Florida Agricultural Experiment Station


SCREW PRESS
FLOW AND MATERIAL BALANCE SHEET
COLD PRESSED CITRUS PEEL OIL MANUFACTURE

AQUEOUS PHASE 190 GAL./GAL. OIL
YIELD 4.90 LB. OIL/TON PEEL
VARIETY MIDSEASON ORANGES


SARClOH E 1R4e


IJAME s. NIFrFion
OWER I. "CDUFF


Fig. 3.-Flow and material balance sheet for process using screw press.


Fraser Brace Extractor.-Whole fruit is passed through a
corridor of carborundum rolls in this process, as shown in Fig. 4.
As the fruit passes through the extractor it is turned over and
over and abrasive rolls rasp the flavedo from the fruit. Water






Florida Citrus Oils


CROSS SECTION 3-TUNNEL GRATER


Fig. 4.-Cross-section diagram of Fraser Brace extractor. (Courtesy
Fraser Brace Engineering Co., Tampa.)

sprays are directed onto the fruit and rolls to wash away the
oil and grated peel. The oil and water emulsion is passed over
a screen to remove the suspended solid particles and then trans-
ferred to settling tanks in which it is held from three to 12
hours to effect complete settling and to allow the emulsion to
break. The machine is completely enclosed and very little loss
of oil is encountered. Figure 5 is a flow and material balance
sheet for this process.
Pipkin Juice Extractor.-The Pipkin Juice Extractor (Fig. 6)
provides a method whereby both the juice and the peel oil from
whole fruit are secured simultaneously, but in such a manner
that they do not come in contact with each other to any great
extent. The machine is of the rotary type and has 24 squeezing
heads, which are all actuated by a common cam. The extractor
is furnished complete with a feeder mechanism and a built-in
electric power unit. The whole fruit is fed into a squeezing cup
where just enough pressure is applied to remove all of the juice







Florida Agricultural Experiment Station


FRASER BRACE EXTRACTOR
FLOW AND MATERIAL BALANCE SHEET
COLD PRESED CITRUS PEEL OIL MANUFACTURE
AQUEOUS PHASE 1o00 AL./AL.OIL
YIELD .TO0 LR OIL/TON PEEL
VARIETY MIDSEASON ORANGES
SPRAY NOZZLS 1. 0, ,1 4
EXTRACTORI 4 7
STORAGE TANKS R, I II. 1,I1


MARCH SI) IS


Fig. 5.-Flow and material balance sheet for process using Fraser
Brace extractor.


from the fruit and at the same time rupture the oil cells. The
juice and the oil emulsion are collected in separate trough
assemblies. The flow and material balance sheet for this process
is given in Fig. 7.

DISTILLED OILS

Distilled oil of orange, grapefruit, or tangerine is secured by
some processors as a by-product in the canning of citrus fruit


JAMlW. KESTEROM
OnR .cDurfP






Florida Citrus Oils


juices. Some of the citrus peel oil becomes mixed with the
juice as it is extracted by the various types of juice extractors
used in the canneries. Excessive amounts of peel oil in the
juice are detrimental to the quality of the canned juice; there-
fore, in most canning plants the oil content of the juice is re-
duced to a desirable level by passing the juice through a deoiler.
The juice is usually flashed in the deoiler, which is operated
under a vacuum of 11 in. (1900 F.) to 25.5 in. (130 F.), and
a vapor mixture of oil and water is removed. Then the mixture
of oil and water vapors is condensed and the oil is separated
from the condensate by decantation or centrifuging. Vacuum
steam distilled oils, which are manufactured in this manner,
will have slightly different properties from oils which are ob-
tained by steam distillation at atmospheric pressure.
Stripper oils are obtained as a by-product from the manu-
facture of citrus molasses, which is made from the press liquor

Fig. 6.-Pipkin juice extractor. (Photograph courtesy Food Machinery
Corp., Lakeland, Fla.)







Florida Agricultural Experiment Station


PIPKIN JUICE EXTRACTOR
FLOW AND MATERIAL BALANCE SHEET
COLD PRESSED CITRUS PEEL OIL MANUFACTURE
AQUEOUS PHASE 12.5 GAL./ GAL. OIL
YIELD 7.0 LB. OIL / TON PEEL
VARIETY MIDSEASON ORANGES


Fig. 7.-Flow and material balance sheet for process using Pipkin
juice extractor.

from plants manufacturing dried citrus pulp for cattle feed.
Press liquor results when limed, shredded citrus peel is pressed
prior to drying. Citrus peel oil is present in this press liquor
and is usually removed by heating the latter to 230 to 240 F.
and then flashing at atmospheric pressure. Stripper oil is usually
a mixture of citrus oils, since the press liquor is often obtained
from a mixture of orange and grapefruit peel.






Florida Citrus Oils


Distilled oil of lime is manufactured in Florida from cannery
peel. The peel is first passed through a Pipkin roll in order to
secure some coldpressed oil; then it is mashed or chopped and
finally steam distilled at atmospheric pressure. Figure 8 shows
an installation for the manufacture of expressed and distilled
oil of lime, and the flow diagram for this commercial process is
given in Fig. 9.

EXPERIMENTAL PROCEDURE
SURVEY OF COMMERCIAL PLANTS
Information pertaining to the various processes used in Florida
for the manufacture of expressed and distilled citrus peel oils
was secured through the helpful cooperation of commercial pro-
cessors. In order to secure the data used in the preparation
of flow and material balance sheets, the authors visited plants

Fig. 8.-Installation for the manufacture of Florida expressed and
distilled oil of lime.






Florida Agricultural Experiment Station


Fig. 9.-Flow sheet for the manufacture of Florida expressed and
distilled oil of lime.
employing the various methods of oil extraction. Rate of flow
measurements were made on each unit process operation for each
individual process. Data were taken covering periods of oper-
ation of four to 24 hours' duration. Information obtained from
each study was incorporated in a flow and material balance dia-
gram for that particular process, and these are presented in
Figs. 2, 3, 5, 7, and 9.
COLLECTION OF SAMPLES
A total of 83 samples of various types of coldpressed and dis-
tilled citrus oils was secured from commercial processing plants
during the 1947-48 season.






Florida Citrus Oils


Forty-two samples of coldpressed oils of orange, grapefruit,
and tangerine were secured from four plants, each of which was
using a different method for the extraction of the oil from the
peel. These samples were taken once a month from lots of oil
ranging from 500 to 11,000 pounds, which represented the pro-
duction for approximately one week.
One plant furnished 12 samples of expressed orange oil, which
were analyzed to determine if storage of the fruit for several
days prior to the extraction of the oil would cause any change
in the physical and chemical characteristics of the oil. Part of
a selected lot of Valencia oranges was processed through the
oil plant on the day it was picked and an equal quantity of the
same lot of fruit was held in storage bins from three to five
days before the oil was extracted. Each comparative set of
samples was made by the same type of extractor under exactly
the same conditions. These 12 samples were representative of
132,000 pounds of oil that was extracted from approximately
840,000 boxes of fruit.
Samples of distilled oils of orange and grapefruit from 250
to 350-pound batches of oil were collected from five canneries
and a total of 18 samples were secured. Only one sample of dis-
tilled tangerine oil representing 35 pounds was obtained. The
six samples of expressed oil of lime, the five samples of distilled
lime oil, and the one sample of distilled oil from Meyer lemon were
obtained from one commercial processing plant during July and
August 1948. These samples represented the coldpressed oil
which was expressed from 3,850 boxes of Persian limes. After
the removal of the coldpressed oil, 1,100 of these boxes were
subsequently steam distilled to produce the distilled oil of lime.
The sample of Meyer lemon oil was secured by the distillation
of the peel from 25 boxes of this fruit.

METHODS OF ANALYSES
The physical properties of the original oils and the 10 percent
distillates were determined by the Official and Tentative Methods
of Analysis of the Association of Official Agricultural Chemists
(1). The specific gravity was determined at 250C./250C. and
the optical rotation at 25C. as recommended by the United
States Pharmacopoeia (24).
The aldehyde content of the oils was determined by the
hydroxylamine method, a standard procedure for which is given
by Guenther (12). The final end point for the reaction was ob-
tained by using a titrimeter rather than the bromphenol blue







Florida Agricultural Experiment Station


indicator. All of the aldehyde values were calculated as decyl
aldehyde, except those for the lime and Meyer lemon oils, which
were calculated as citral.
The method of Seeker and Kirby as reported by Poore (23)
was used for the determination of esters. In this method the
aldehydes present are removed with hydroxylamine hydrochlor-
ide prior to the saponification of the esters.
The evaporation residue was determined by a method very
similar to that given by Guenther (12). A watch glass (100
mm. in diameter) was used in place of an evaporating dish, and
after having been heated on the steam bath for the prescribed
length of time the watch glass was transferred to an oven at
100' C. and dried for one hour.

EXPERIMENTAL RESULTS
COLDPRESSED OIL OF ORANGE
The physical and chemical properties of samples of coldpressed
oil of orange, which were secured from four commercial plants
each month from October 1947 through May 1948, are presented
in Table 2. Each of the four plants used a different method for
expressing the oil. These data are also shown graphically in
Figs. 10 to 15 inclusive.

0 PIPKIN JUICE EXTRACTOR
(D SCREW PRESS
PIPKIN ROLL
e FRASER BRACE EXTRACTOR
0.846 ----------------------------------------------------------
C, U.S.P. XIII
0.842
TO
o 0.845 0.846
I-

S0.844


0.843


A0.84
0.842---------- ----------- ---- ...... ........

OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY
Fig. 10.-Specific gravity of coldpressed orange oils extracted by four
different methods during the 1947-48 season.




TAB E. .-THE PHYSIC AND CHEMICAL PROPERTIES OF COLDP SSED ORAN E O. S PRODUCED IN .LORIDA.
Refrac-
Refrac- tive Optical Alde- Evapor-
Type tive Index Optical Rotation hyde Ester ation
of Variety Specific Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Extractor of Gravity 20 Distillate ence 25 Distillate ence tent tent due
Fruit* 25C./25C. n D 20 D 25 % %
n cc % % %
DD ID
October, 1947
Pipkin juice I
extractor 100% H | 0.8433 | 1.4729 1.4714 0.0015 +97.57 +97.75 0.18 1.17 0.44 2.52
50% H
Screw press 50% PB 0.8419 1.4723 1.4708 0.0015 +97.57 +97.75 0.18 1.01 0.42 2.20
November, 1947
Pipkin juice 25% H I
extractor 75% P&S 0.8433 1.4728 [ 1.4715 I 0.0013 I +97.01 +97.05 0.04 1.31 0.38 2.59
50% H
Screw press 50% PB 0.8422 1.4724 1.4709 0.0015 +97.57 +97.60 0.03 0.92 0.30 2.02
December, 1947
10% H II I
Pipkin juice 50% P I I
extractor 40% S 0.8426 1.4725 1.4712 0.0013 +97.01 +97.06 0.05 1.63 0.33 2.18
50% H
Screw press 50% PB 0.8420 1.4723 I 1.4709 0.0014 +97.53 +97.60 0.07 1.34 0.48 1.77
January, 1948
Fraser Brace 50% P
extractor 50% S 0.8458 1.4733 1.4709 0.0024 +95.16 +97.12 1.96 1.08 1.45 4.81
60% S
Pipkin juice 35% _P
extractor 5% H 0.8426 1.4724 1.4709 0.0015 +96.81 +96.81 0.00 1.74 0.42 1.94
50% P
Screw press 50% S 0.8416 1.4721 1.4707 0.0014 +97.49 +97.52 0.03 1.55 0.33 1.38
February, 1948
Fraser Brace 50% P | P
extractor 50% S 0.8453 1.4734 1.4703 0.0031 +95.16 +97.12 1.96 1.08 1.50 4.93
Pipkin juice 50% P I
extractor 50% S 0.8430 1.4724 1.4710 0.0014 +96.81 +97.37 0.56 1.78 0.38 2.19
45% P
45% S
Screw press 10% V 0.8420 1.4723 1.4710 0.0013 +97.13 +97.54 0.41 1.41 0.20 1.68




TABLE 2.-THE PHYSICAL AND CHEMICAL PROPERTIES OF COLPRESSED ORANGE OILS PRODUCED IN FLORIDA-(Concluded).

I Refrac-
Refrac- tive Optical Aide- Evapor-
Type Variety Specific tive Index Differ- Optical Rotation Differ- hyde Ester ation
of of Gravity Index of 10% ence Rotation of 10% ence Con- Con- Resi-
Extractor Fruit* 25C./25C. 20 Distillate 25 Distillate tent tent due
D n 20 D c 25 % % %
Dc D
50% P II
P;l.~ili roll 50% S 0.8424 1.4722 i 1.4709 0.0013 +97.76 +97.77 0.01 1.70 0.15 1.49
__March, 1948
Fraser Brace 50% P I
extractor 50% S 0.8449 1.4734 1.4710 0.0024 +95.21 +96.96 1.75 1.64 0.35 3.70
Pipkin juice |
extractor 100% V 0.8428 1.4723 1.4708 0.0015 +96.61 +96.96 0.35 2.04 0.08 2.08
50% P P
Screw press 50% P&S 0.8421 1.4719 1.4711 0.0008 +97.04 +97.24 0.20 1.52 0.04 1.95

Pipkin roll 100% V 0.8420 1.4718 1.4708 0.0010 +97.34 +98.19 0.85 1.98 0.34 1.07
___April, 1948
Fraser Brace I
extractor 100% V 0.8441 1.4730 1.4713 0.0017 +96.10 +97.61 1.51 1.65 0.97 3.12
Pipkin juice
extractor 100% V 0.8431 1.4725 1.4712 0.0013 +96.19 +97.21 1.02 1.97 0.53 2.09

Screw press 100% V 0.8420 1.4722 1.4711 0.0011 +93.69 +97.25 0.56 1.52 0.53 1.71

Pipkin roll 100% V 0.8423 1.4721 1.4711 0.0010 +97.16 +97.52 0.36 2.02 0.39 1.31
May, 1948
Fraser Brace
extractor 100% V 0.8455 1 1.4733 | 1.4713 0.0020 +95.66 +98.10 2.44 1.45 1.50 3.99
Pipkin juice
extractor 100% V 0.8431 1.4723 1.4710 0.0013 +96.66 +97.83 1.17 1.77 0.91 2.36

Screw press 100% V 0.8426 1.4721 1.4712 0.0009 +97.59 +98.32 0.73 1.38 1 0.95 2.11

Pipkin roll 100% V 0.8425 1.4719 1.4710 0.0009 +97.73 +98.19 0.46 1.72 1.01 1.57
H = Hamlin, PB = Parson Brown, P = Pineapple, S = Seedling, V = Valencia.







Florida Citrus Oils


0 PIPKII JUICE EXTRACTOR
1.474 SCREW PRESS
PIPKIN ROLL -....---- -----------------------------..
SFRASER BRACE EXTRACTOR










SU.S.P. XIII
1.472 1.4725
0TO
w






4 1.4737




1.471 -. .
OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY
Fig. 11.-Refractive index of coldpressed orange oils extracted by four
different methods during the 1947-48 season.
0 PIPKIN JUICE EXTRACTOR
D SCREW PRESS
+99*'0 PIPKIN ROLL ----------------------
FRASER BRACE EXTRACTOR

o 9 +

z
I,-
















U.S.P. XIII
NOT LESS THAN
+*940
NOT MORE THAN
@99"
+ 94f l l --------------- -- ----..-

OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY
Fig. 12.-Optical rotation of coldpressed orange oils extracted by four
different methods during the 1947-48 season.






Florida Agricultural Experiment Station


'O PIPKIN JUICE EXTRACTOR
0 SCREW PRESS
SPIPKIN ROLL
0 FRASER BRACE EXTRACTOR


5.0




4.0




S3.0








W
oi


U.S.P. XIII
NOT LESS THAN
1.7%


OCT. NOV. DEC. JAN. FEB. MAR, APR. MAY
Fig. 13.-Evaporation residue of coldpressed orange oils extracted by four
different methods di;ring the 1947-48 season.

O PIPKIN JUICE EXTRACTOR
D SCREW PRESS
( PIPKIN ROLL
I_ O FRASER BRACE EXTRACTOR r


L


OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY

Fig. 14.-Aldehyde content of coldpressed orange oils extracted by four-
different methods during the 1947-48 season.






Florida Citrus Oils


0 PIPKIN JUICE EXTRACTOR
a SCREW PRESS
9 PIPKIN ROLL
O FRASER BRACE EXTRACTOR


I.O0


0.s5


U.U B .. ..
OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY
Fig. 15.-Ester content of coldpressed orange oils extracted by four
different methods during the 1947-48 season.


O SPECIFIC GRAVITY
9 EVAPORATION RESIDUE


S 2 3 4 5 6 7 8 9 10
YIELD- LB.OIL/TON PEEL
Fig. 16.-Relation of specific gravity and evaporation residue of coldpressed
orange oils to yield.

Data secured at the various processing plants pertaining to
the yields of oil obtained by the different methods of extraction







26 Florida Agricultural Experiment Station


are presented in Table 3 and Figs. 2, 3, 5, and 7. Table 3 also
shows the relationship between the yields of coldpressed orange
oils, which were obtained by the four methods of extraction,
and all of the physical and chemical properties of the oils, except
the aldehyde content. Data for all four of the different methods
of extraction are not available for the months prior to February;
therefore, they could not be used to secure average values for
comparison purposes. The data presented are average values
for the three months, March, April, and May, and also were


0o


0 OPTICAL ROTATION
REFRACTIVE INDEX


1.4721-


+99*


+98*
r
+970 =


+96* g


+950
o24


IAT711


I 2 3 4 5 6 7
YIELD LB. OIL/TON PEEL
Fig. 17.-Relation of refractive index and optical
orange oils to yield.


1.-
I-

0
o
ac
I-
hi


8 9 10


rotation of coldpressed


Fig. 18.-Relation of ester content of coldpressed orange oils to yield.


1 2 3 4 5 6 7 8 9 10
YIELD LB. OIL/ TON PEEL


W%


r'


v.v


,,







Florida Citrus Oils


TABLE 3.-RELATION OF YIELD TO THE CHARACTERISTICS OF FLORIDIAN
OIL OF ORANGE.



o0 a Method
E 0 of
-d c Extraction
p, aC) 0 0 2 W

9.70 .8448 3.60 +95.66 1.4732 0.94 Fraser Brace
_________________ ____________ extractor
7.00 .8430 2.18 +96.49 1.4724 0.51 Pipkin juice
extractor
4.90 .8422 1.92 +97.11 1.4721 0.51 Screw press

1.85 .8423 1.32 +97.41 1.4719 0.58 Pipkin roll


secured during those months when only one variety, Valencia,
of oranges was being processed. Figures 16, 17, and 18 present
these results in graphic form.
The relationship between the aldehyde content of expressed
oil of orange and the quantity of aqueous phase, which comes
in contact with the oil during processing, can be seen in Table
4 and Fig. 19. Here, also, the average values for the aldehyde
content of samples of oil secured during March, April, and May
are used. The results secured for oils which were extracted dur-
ing January and February by the Fraser Brace extractor were
not included in these average values because a basic change was

TABLE 4.-EFFECT OF QUANTITY OF AQUEOUS PHASE ON THE ALDEHYDE
CONTENT OF FLORIDIAN OIL OF ORANGE.
Aqueous Phase Aldehyde Content Method of
Gal./Gal. Oil % Extraction

12.5 1.93 Pipkin juice extractor

21.5 1.91 Pipkin roll

100.0 1.58 Fraser Brace extractor

190.0 1.47 Screw press






Florida Agricultural Experiment Station


made in this processing method after these samples of oil had
been obtained. Extremely large quantities of water were being
used with this extractor during January and February. In
March the amount of water used was reduced to give 100 gallons
of an aqueous phase per gallon of oil produced and the oil ex-
tracted in that month contained 52 percent more aldehyde than
the February sample.
The analyses of samples of expressed oil of orange, extracted
during March, April, May, and June from Valencia oranges by
the Pipkin juice extractor, are given in Tables 5 and 6. Values
in Table 5 are for oil which was extracted from fruit on the day
it was harvested; the data in Table 6 refer to oil extracted from
fruit which was held in storage bins from three to five days prior
to its extraction. The differences between the average values
of the properties of the oils immediately extracted and the oils
extracted from the stored fruit are presented in Table 7. Sig-
nificant differences were found only in the chemical properties
of these oils.

COLDPRESSED AND DISTILLED OILS OF ORANGE, GRAPEFRUIT,
TANGERINE, AND LIME
Table 8 includes the maximum and minimum values of the
physical and chemical characteristics of coldpressed and distilled


~2.0




0
0
W 1.5
z





1.0 r
0 50 100 150 200
AQUEOUS PHASE= GAL./GAL. OIL
Fig. 19.-Influence of the quantity of aqueous phase which comes in
contact with the oil during processing on the aldehyde content of coldpressed
orange oils.









TABLE 5.-PROPERTIES OF OIL OF ORANGE EXPRESSED FROM FRUIT ON THE DAY HARVESTED.
Refrac-
Refrac- tive Optical Alde- Evapor-
Quantity Variety Specific tive Index Opitical Rotation hyde Ester ation
Date of Oil of Gravity Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Sampled Fruit 25*C./25C. 20 Distillate ence 25 Distillate ence tent tent due
Lb. nD 20 D 25 % % %
D D
3-22-48 11,000* Valencia 0.8428 1.4723 1.4708 .0015 +96.61 +96.96 0.35 2.04 0.08 1 2.08
4-8-48 11,000 Valencia 0.8427 1.4725 1.4714 .0011 +96.38 +97.44 1.06 1.94 0.53 2.07
4-14-48 11,000 Valencia 0.8431 1.4725 1.4712 .0013 +96.19 +97.21 1.02 1.97 0.53 2.09
5-10-48 11,000 Valencia 0.8427 1.4722 1.4712 .0010 +97.26 +97.76 0.50 1.84 0.71 I 1.85
6-1-48 11,000 Valencia 0.8428 1.4719 1.4707 .0012 +97.29 +97.77 0.48 1.65 0.60 1.98
6-21-48 11,000 Valencia 0.8427 1.4719 1.4709 .0010 +96.97 +98.37 1.40 1.45 0.45 1.74
Average 0.8428 1.4722 1.4710 .0012 +96.78 +_97.58 0.80 1.82 0.48 1.97
Each 11,000 pounds of oil represents approximately 70,000 boxes of fruit.












TABLE 6.-PROPERTIES OF OIL OF ORANGE EXPRESSED FROM FRUIT STORED IN FRUIT BINS FOR THREE TO FIVE DAYS.

Refrac-
Refrac- tive Optical Alde- Evapor-
Quantity Variety Specific tive Index Opitical Rotation hyde Ester ation
Date of Oil of Gravity Index of 10% Differ- Rotation of 10% Differ- Con- Con- Resi-
Sampled Fruit 25C./25C. 20 Distillate ence 25 Distillate ence tent tent due
Lb. nD 20 D 25 %
n D cc D
3-19-48 11,000* Valencia 0.8430 1.4723 1.4708 .0015 +96.61 +96.96 0.35 1.92 0.25 2.07

4-10-48 11,000 Valencia 0.8426 1.4725 1.4710 .0015 +96.39 +97.23 0.84 1.89 0.60 2.17

4-14-48 11,000 Valencia 0.8432 1.4723 1.4709 .0014 +96.52 +97.20 0.68 1.89 0.63 2.33

5-10-48 11,000 Valencia 0.8421 1.4722 1.4711 .0011 +96.78 +97.50 0.72 1.76 0.86 2.18

6-1-48 11,000 Valencia 0.8428 1.4720 1.4709 .0011 +96.89 +98.17 1.28 1.59 0.77 2.14

6-21-48 11,000 Valencia 0.8426 1.4719 1.4708 .0011 +97.29 +98.37 1.08 1.40 0.68 2.09

Average 0.8427 1.4722 1.4709 .0013 +96.74 +97.57 0.83 1.74 0.63 2.16
Each 11,000 pounds of oil represents approximately 70,000 boxes of fruit.











TABLE 7.-INFLUENCE OF STORAGE OF FRUIT, PRIOR TO EXTRACTION, ON THE PROPERTIES OF COLDPRESSED OIL OF ORANGE.
Oil Expressed Oil Expressed
from Fruit Soon from Fruit %
After Harvesting After Storage Difference Difference
(Table 5) (Table 6)

Specific gravity 25oC./25oC. 0.8428 0.8427 0.0001 Not significant
20
Refractive index n 1.4722 1.4722 0.0000 Not significant

Refractive index 10% distillate n 1.4710 1.4709 0.0001 Not significant

Difference 0.0012 0.0013 0.0001 Not significant
25
Optical rotation cc D +96.78 +96.74 0.04 Not significant

Optical rotation 10% distillate c +97.58 +97.57 0.01 Not significant

Difference 0.80 0.83 0.03 Not significant

Aldehyde content % 1.82 1.74 0.08 4.6

Ester content %_ 0.48 0.63 0.15 31.3

Evaporation residue % 1.97 9 2.16 0.19 9.6






Florida Agricultural Experiment Station


orange oils that were secured during the 1947-48 season. Simi-
lar data for expressed and distilled grapefruit and tangerine oils
are given in Table 9, which also includes results obtained from
the analyses of 10 samples of stripper oils from citrus molasses
plants.
The maximum and minimum values for the properties of ex-
pressed and steam distilled Persian lime oil are listed in Table 10.
Also included in this table are results from the analysis of one
sample of steam distilled oil from Meyer lemon. Properties of
Meyer lemon oil indicate that it is predominantly lemon in char-
acter, although the Meyer lemon is commonly believed to be a
natural hybrid.

DISCUSSION OF RESULTS
RELATION OF YIELD TO PROPERTIES AND U. S. P.
SPECIFICATIONS
The factor found to influence the physical and chemical prop-
erties of coldpressed oil of orange to the greatest extent was the
yield of oil secured from the peel. As shown in Table 3 and
Figs. 16 and 17, as the yield increased the values of the specific
gravity, evaporation residue, and refractive index also increased,
but the values of the optical rotation decreased. Thus the per-
centage of the total amount of oil in the peel that is extracted
determines the characteristics of the oil and, therefore, its final
quality. As the yield of oil is increased, more high-boiling,
high-molecular weight constituents are evidently extracted, and
the presence of a greater percentage of these compounds in the
oil causes a reduction in the percentage of d-limonene, resulting
in lower optical rotation values, since d-limonene is the most
optically active component in the oil.
The yield of oil obtained by the various methods of processing
varied from 1.85 lbs./ton peel to 9.70 lbs./ton peel. Commercial
plants often have more peel than it is possible for them to process
and still obtain the maximum amount of oil recoverable from
the peel. This being the case, the plants are operated in such
a manner as to produce the maximum amount of oil on an hourly
basis. To do this they partially extract the oil from a large
quantity of peel rather than secure the maximum recovery of
oil from a smaller quantity of peel. By operating in this manner
they may secure very low yields of oil, despite the fact that they
are capable of obtaining much higher yields with the use of the
same equipment. The yields of oil secured using the Pipkin






TABLE 8.-MAXIMUM AND MINIMUM VALUES FOR THE PHYSICAL AND CHEMICAL PROPERTIES OF ORANGE OILS PRODUCED IN FLORIDA
DURING 1947-48 SEASON.
Vacumm
Type of Oil Coldpressed Steam
___Distilled
Fraser Pipkin
Method of Extraction All Pipkin Screw Brace Juice De-Oiler Oil
Methods Roll Press Extractor Extractor
Number of samples analyzed 35 4 8 6 17 9
Maxi- Mini- Maxi- Mini- Maxi- Mini- Maxi- Mini- Maxi- Mini- Maxi- Mini-
mum mum mum mum mum mum mum mum mum mum mum mum
Specific gravity 25C./25C. 0.8458 0.8416 0.8425 0.8420 0.8426 0.8416 0.8458 0.8441 0.8433 0.8420 0.8464] 0.8400
20 index.4720
Refractive index n 21.4734 1.4718 1.4722 1.4718 1.4724 1.4719 1.4734 1.4730 1.4729 1.4722 1.4732 1.4715
Refractive index of 10% distillate n 20 1.4715 1.4703 1.4711 1.4708 1.4712 1.4707 1.4713 1.4703 1.4715 1.4707 ..

Difference 0.0031 0.0008 0.0013 0.0009 0.0015 0.0008 0.0031 0.0017 0.0015 0.0010] .... .
Optical rotation oc D5 +97.76 +95.16 +97.76 +97.16 +97.59 +96.69 +96.30 +95.16 +97.57 +96.19 +98.56 +95.92
Optical rotation of 10% distillate cc +98.70 +96.81 +98.19 +97.52 +98.32 +97.24 +98.70 +96.961 +97.89 +96.81 .... ...

Difference 2.44 0.00 0.85 0.01 0.73 0.03 2.44 1.51 1.30 0.00 ...
Aldehyde content % 2.041 0.92 2.02 1.70 1.55 0.92 1.65 1.08 2.04 1.17 2.48 1.72
Ester content % 1.63 0.04 1.01 0.15 0.95 0.04 1.63 0.35 1.09 0.08 1.38 0.22
Evaporation residue % 4 4.93 1.07 1.57 1.07 2.20 1.38 4.93 3.12 2.59 1.85 1.24 0.08








TABLE 9.-MAXIMUM AND MINIMUM VALUES FOR THE PHYSICAL AND CHEMICAL PROPERTIES OF SOME CITRUS OILS PRODUCED
IN FLORIDA DURING 1947-48 SEASON.

Type of Oil Grapefruit Tangerine Stripper Oil**
Number of samples analyzed 6 9 1 1 10
Cold- Dis-
Coldpressed Distilled* pressed tilled Distilled

I MaximumM MinimumMaximum Minimum Maximum Minimum
Specific gravity 25C./25oC. 0.8532 0.8508 0.8539 0.8415 0.8456 0.8407 0.8443 0.8398
Refractive index n 2D 1.4761 1.4746 1.4746 1.4714 1.4734 1.4720 1.4721 1.4713
Refractive index of 10% distillate n 1.12 69 1.4711
D 1.4712 1.4698 1.4711
Difference 0.0054 0.0038 .... .... 0.0023 .....
Optical rotation a D +92.96 +91.19 +96.50 +91.50 +91.18 +93.67 +98.90 +95.55
Optical rotation of 10% distillate c 2D +98.14 +95.81 .... .... +92.68 .... ...

Difference 6.33 3.68 .... .... 1.50 ........ .
Aldehyde content % 1.67 1.49 4.06 2.30 1.08 1.24 1.50 0.47
Ester content % 0 4.20 2.11 2.52 0.08 0.34 0.25 2.46 0.07
Evaporation residue % 8.02 6.02 3.66 0.19 4.53 0.20 0.79 0.03
Vacuum steam distilled (de-oiler oil).
** By-product from manufacture of citrus molasses.








TABLE 10.-CHARACTERISTICS OF ESSENTIAL OILS SECURED FROM PERSIAN LIME AND MEYER LEMON.

Type of Oil Persian Lime Meyer Lemon
Number of samples 6 5 1

Coldpressed Steam Distilled Steam Distilled
_____Maximum Minimum Maximum Minimum_
Specific gravity 20'C./20'C. 0.8823 0.8798 0.8579 0.8556 0.8555
Refractive index n D 1.4853 1.4842 1.4751 1.4743 1.4740
Refractive index of 10% distillate n 1.4731 1.4729 ...

Difference 0.0123 0.0112 .... _.....
20 1
Optical rotation cc _D +41.80 +-38.60 +50.52 +46.84 +56.00
Optical rotation of 10% distillate oc ) +49.24 +47.60 .... .

Difference 9.88 7.00 __ ........ __
Aldehyde content % 5.52 3.66 2.71 1.61 1.19
Ester content % I 8.20 7.42 3.49 2.41 2.45
Evaporation residue %1 14.67 12.95 1.23 0.18 0.16







Florida Agricultural Experiment Station


roll and screw press methods of extraction, as shown in Table 3,
appear to be low when compared to the yields obtained by the
other methods of extraction, but this is caused by the operation
of the equipment from an efficiency standpoint on an hourly
rather than a yield basis. Quality of the oil depends upon its
properties, which are influenced by the yield obtained, which
in turn is determined by operational procedure of the equipment
used and other processing techniques.
Analyses of expressed oils of orange secured during the
1947-48 season indicate that the oil produced by some of the
manufacturing processes at certain times during the season did
not meet the U. S. P. (24) specifications, because some of the
processes resulted in yields which were too low or too high.
Only one method of extraction gave yields throughout the season
so that the oil consistently met the requirements of the U. S. P.
However, it is apparent that if oil is extracted in such manner
that the yield falls within a certain range, then it will meet
U. S. P. specifications.
Utilization of data obtained during this investigation will
make it possible for any processor to produce an oil which will
meet U. S. P. specifications, provided he is willing to change
his manufacturing procedures. He may still use available equip-
ment in such manner that he will secure a yield of oil having
these properties which are indicative of good quality. Exces-
sively high or low yields should be decreased or increased by
the mode of operation of the extraction equipment. Based upon
the data accumulated during the past year, it is estimated that
a yield of 6.5 to 8.5 pounds of oil per ton of peel from mid-season
oranges or the extraction of 45 to 60 percent of the total amount
of oil in the peel of any variety of fruit of good maturity will
result in a coldpressed oil of orange that will meet the specifica-
tions of the United States Pharmacopoeia (24). It might also
be added that oil extracted about the middle of May from Va-
lencia oranges which had passed peak maturity did not meet
U. S. P. standards. The reason that this late-season oil was of
lower quality was that low yields of oil were obtained with this
type of fruit because the peel had become soft and pliable, mak-
ing the extraction of the oil more difficult.
EFFECT OF AQUEOUS PHASE ON ALDEHYDE CONTENT
The flavor quality of oil of orange is dependent upon the many
constituents of which it is composed. The aldehyde content of
the oil, although not included in the U. S. P. specifications, is






Florida Citrus Oils


indicative of the flavoring qualities of the oil. Although other
constituents are also very important from a flavor standpoint,
aldehydes are a predominant factor in orange and other citrus
oils. The data in Table 4 and Fig. 19 indicate that the aldehyde
content decreases as the amount of aqueous phase which comes
in contact with the oil during processing is increased. The
average aldehyde content of the expressed oils of orange, secured
during March, April, and May from the four plants at which
material balance studies were made, varied from 1.47 to 1.93
percent. In one plant, where, at the suggestion of the authors,
the water used in the process was reduced from extremely large
quantities to an amount sufficient to give 100 gallons of aqueous
phase per gallon of oil produced, while other variable factors
were kept constant, the aldehyde content increased from 1.08
to 1.64 percent, or 52 percent. Thus, it is evident that to pro-
duce an orange oil of high aldehyde content, the amount of aque-
ous phase allowed to come in contact with the oil during process-
ing should be reduced to as small a quantity as is practically
possible under operating conditions.

RELATION OF FRUIT VARIETY TO PROPERTIES
Consideration of Table 2 and Figs. 10, 11, and 12 shows that
the oils manufactured by any one process fell within a particular
category of their own and remained there throughout the season.
The differences in the physical properties of expressed orange
oils that were obtained from different varieties of fruit by any
particular process were not significant, except in the case of the
Fraser Brace method of extraction where, during the month
of April, an apparently erratic variation occurred.
The aldehyde content of coldpressed oils of orange, as can
be seen from Table 2 and Fig. 14, was highest when made from
Valencia oranges. Mixtures of Pineapple and seedling oranges
gave an oil with a lower aldehyde content, and mixtures of
Hamlin and Parson Brown varieties yielded the lowest aldehyde
content oil.
The variety of the fruit apparently had very little effect on
the ester content of the orange oils. Oil of orange produced by
the Fraser Brace extractor from mid-season varieties that were
partially green in color was considerably higher in ester content
than that made by the same process later in the season from
the same varieties when they were completely orange in color,
and it was also higher in esters than oils produced by the other





Florida Agricultural Experiment Station


methods. High evaporation residue values also were found for
the oils produced by the Fraser Brace extractor.
STORAGE OF FRUIT PRIOR TO OIL EXTRACTION
Results obtained indicate that the length of time fruit was
stored prior to the extraction of the oil was another factor which
influenced the characteristics and quality of the oil. This is
illustrated by the data presented in Tables 5, 6, and 7, which
show the effect storage of the fruit had upon the physical and
chemical properties of the oil. There were no significant differ-
ences in the physical properties of coldpressed oils of orange
extracted from fruit on the same day it was harvested and those
extracted from fruit having been stored in fruit bins for three
to five days before the oils were extracted. However, significant
differences were found in the chemical properties. The ester
content of the oil secured from stored fruit was 31.3 percent
higher than that extracted from fruit which had not been stored.
The evaporation residue of the oil from the stored fruit was 9.6
percent greater and the aldehyde content was 4.6 percent
smaller than these properties of the oil from the fruit which
was not stored.
EFFECT OF MATURITY ON PROPERTIES
In the studies of the effect of fruit storage on oil quality,
all samples of the oil of orange were extracted by the same
process and secured from the same variety of fruit. Therefore,
over a period of four months information was obtained in refer-
ence to the effect of maturity on the properties of the oil. Here,
again, differences were noted in the chemical characteristics
rather than in the physical properties. The aldehyde content
of Valencia orange oils increased as maturity increased, reached
a maximum when extracted during the early part of the Valencia
season from fruit that just passed the maturity standards, and
then decreased after peak maturity had been reached. The
ester content of these oils was lowest when extracted during
the early part of the Valencia season and gradually increased
as the fruit became more mature. Valencia oranges that had
passed peak maturity produced an oil with the highest ester
content of any oils secured during the year.

COMPARISON OF COLDPRESSED AND DISTILLED OILS
Comparison in Table 8 of the analyses of coldpressed oils of
orange with those of vacuum steam distilled oils of orange,







Florida Citrus Oils


which were secured from the cannery deoilers, showed that the
distilled oils had an aldehyde content 24 percent higher and an
ester content 10 percent lower than the corresponding values
for coldpressed oils. Similarly, as seen in Table 9, distilled oil
of grapefruit was 90 percent higher in aldehydes and 60 percent
lower in esters than the expressed oil. From these results it
was evident that large quantities of aldehydes were removed
from the citrus juice itself by the deoilers during commercial
canning'operations. Also it is indicated that the removal of oil
from the juice by the deoilers results in the fractionation of the
peel oil originally present, so that the small quantity of oil which
remains in the canned juice will have different characteristics
from either expressed or distilled oils.
A comparison of the properties of stripper oils that were
obtained from the press liquor in citrus molasses plants with
the properties of other types of oils cannot be made because the
press liquor was often obtained from a mixture of orange and
grapefruit peel.

COMPARISON OF FLORIDIAN ESSENTIAL OILS WITH OILS
FROM OTHER SOURCES
Data presented in Tables 11 and 12 show how various types
of Floridian essential oils compare with similar types of oils
from California and various foreign countries. All of the data
in these tables for Floridian oils are based on results secured
during this investigation. The data for the oils from other
sources are those given by Guenther (7), (8), (9), (10) and
are based upon the analysis of many samples of these oils in
the laboratories of Fritzsche Brothers, Inc., New York. From
the comparison of the properties presented in these tables it is
evident that Florida citrus oils can be equal or superior to essen-
tial oils from any other source. Further research is being under-
taken in reference to the flavoring qualities of the essential oils
produced in Florida in order to demonstrate that they can con-
sistently be manufactured with high flavoring quality.

SUMMARY
Commercial methods of production of essential oils in Florida
during the 1947-48 season have been studied and compared.
The physical and chemical properties of 83 samples of cold-
pressed and distilled oils of orange, grapefruit, tangerine, and
lime have been determined. Properties of Meyer lemon oil and












TABLE 11.-COMPARISON OF FLORIDIAN COLDPRESSED ORANGE OIL WITH OILS FROM OTHER SOURCES.

U.S.P. XIII Floridian Californian Italian Guinea Brazilian
Specifications Coldpressed Orange Coldpressed Coldpressed Coldpressed Coldpressed
Coldpressed Orange Orange Orange Orange
Orange Maxi- Mini- Maxi- Mini- Mai- Mini- Mai- Mini- Mai- Mini-
___mum mum Average mum mum mum mum mum mum mum mum
Specific 0.842
gravity to 0.846 0.842 0.843 0.846 0.843 0.846 0.843 0.845 0.840 0.847 0.842
(250C./25"C.) 0.846
Refractive 1.4723
index to 1.4734 1.4718 1.4724 1.4742 1.4731 1.4740 1.4729 1.4742 1.4721 1.4747 1.4723
(20C.) 1.4737
Evaporation not less
residue than 4.9 1.1 2.2 5.1 3.5 4.3 1.4 2.4 1.1 4.8 2.2
% 1.7%
not less than
Optical +94 and not
rotation more than +990 +97.76 +95.160 +96.75* +98.33" +94 +97.17" +95.5 +98* +94* +97.87* +95.0*
(25-C.) in 100mm tube _













TABLE 12.-COMPARISON OF FLORIDIAN ORANGE AND LIME OILS WITH OILS FROM OTHER SOURCES.


I ri~df~lloor namo. o


Coldpressed Lime


Distilled Lime


I West Indian West Indian
Fleridian Californian Floridian and Mexican Floridian and Mexican
. .. --.. .... I __ r. 11___ 1_u


Maxi- Mini- Aver- Maxi- Mini-
fIinn a e mumnfll mum


Maxi- Mini- Aver- Maxi- Mini- I Maxi-
mum mum age mum mum mum


Mini-
mum


Aver- 1vMaxi- I YLni-
age mum mum


00 HU001 1 1 *JM.^ ,.... ,-.--- i --r-- ______ __---
Specific 0..0.878856 0.857 0.862
gravity 0.846 0.840 0.842 0.842 0.840 0.882 0.880 0.881 0.886 0.878 0.858 0.856 0.857 0.868 0.862
(25c./25C.) (20"C.) (20C.) (20C.) (15 C.) (15 1C.) (20 0. (20200.) (200C.) (15C.) (15 .)
Refractive 1.4750
index 1.4732 1.4715 1.4720 1.4730 1.4717 1.4853 1.4842 1.4849 1.4860 1.4800 1.4751 1.4743 1.4747 1.4770 1.4750
(20'C.)
(20C.) 1a_473I 2 1.470 _______I _____I II I ______ -- ---------
Evaporation I
residue 1.24 0.08 0.47 1.0 0.5 14.67 12.95 13.74 13.5 10 1.23 0.18 0.60

Optical I 1 ...___ --1- --- -35"
rotation 98.56 1+95.92" +97.621 +99.1" +980 +41.80* +38.600 +40.55" +40* 1+35* +50.52* +46.840 +48.02* +46" +35"
(25oC.) (25"C.) (25'C.) (25C0.) (25C.) (20"C.) (20"C.) (20"C.) ___(200C.) (200C.) (20C.) __


Aldehyde
content-% 2.48* 1.72* 1.99*
(as citral)
As decyl aldehyde.


5.52


3.66 1 4.92


4.5 2.71 1.61 2.03


I






Florida Agricultural Experiment Station


stripper oils also are reported. Coldpressed and distilled oils of
orange and grapefruit were found to have very large differences
in their aldehyde and ester contents.
Fruit variety, degree of maturity, and storage of fruit before
extraction were found to be factors which affected significantly
the chemical properties of expressed oil of orange. These factors
did not affect to any extent the physical characteristics of the oil.
Quality of citrus peel oils, as indicated by their physical and
chemical characteristics, is determined by the yield of oil ob-
tained in any commercial process, regardless of the type of ex-
traction equipment used, and also by the quantity of aqueous
phase that comes in contact with the oil during processing, since
the aldehyde content of the oil is largely determined by this
factor.
The use of proper processing methods results in the produc-
tion of essential oils in Florida which are of the highest quality
and which consistently meet the specifications of the United
States Pharmacopoeia. When manufactured carefully, Florida
citrus oils are equal or superior in quality to essential oils from
any other sources.

ACKNOWLEDGMENTS
Acknowledgments are made to the commercial processors and manu-
facturers in the State of Florida whose earnest cooperation contributed
much to the success of this work. Coldpressed oil samples used in this
study were obtained from Essential Oil Producers, Inc., Dunedin; Pasco
Packing Company, Dade City; Florida Citrus Oil Company, Lake Alfred;
and Fraser Brace Engineering Company, Tampa. The distilled oils were
secured from Florida Citrus Canners Cooperative, Lake Wales; Wm. P.
McDonald Corporation, Auburndale; Floridagold Citrus Corporation, Lake
Alfred; Dr. P. Phillips Canning Company, Orlando; and Essential Oil Pro-
ducers, Inc., Dunedin. The stripper oils were furnished by the Florida
Molasses Corporation, Lake Alfred; Adams Packing Association, Auburn-
dale; Citrus Canners Cooperative, Lake Wales; and Pasco Packing Company,
Dade City. The authors are indebted to Dr. F. W. Wenzel for his contribu-
tion to the organizing and editing of this bulletin. Acknowledgment is
made to V. H. Ragsdale and E. C. Parrish for their assistance in securing
part of the analytical data. For all of these courtesies and contributions
the authors express their appreciation and thanks.

LITERATURE CITED
1. ASSOCIATION OF OFFICIAL AGRICULTURAL CHEMISTS. Official and tenta-
tive methods of analysis. 6th Ed., 932 pp. 1945. Washington,
D. C.
2. ATKINS, C. D., E. WIEDERHOLD, and J. L. HEID. The recovery of







Florida Citrus Oils


flavoring oil from Persian limes-preliminary experiments. The
Fruit Products Jour. and Am. Food Manufacturer. 23: 10: 306-308.
1944.
3. BARTHOLOMEW, E. T., and W. B. SINCLAIR. Factors influencing the
volatile oil content of the peel of immature and mature oranges.
Plant Physiol. 21: 3: 319-331. 1946.
4. DE VILLIERS, F. J. Citrus by-products research: orange oil. Farming
in S. Africa. 4: 515-516, 529. 1930.
5. FOOTE, P. A.; and R. Z. GELPI. Florida volatile oils. IV. Sweet orange.
Jour. Am. Pharm. Assoc. 32: 6: 145-148. 1943.
6. GILDEMEISTER, E., and F. HOFFMAN. Die Aetherischen Oele. 3rd Ed.
Vols. I, II, and III. 1928-1931. Leipzig.
7. Guenther, E. California citrus oils. Am. Perfumer Essent. Oil Rev.
May, June, July, Aug. 1937. Reprint 15 pp.
8. GUENTHER, E. Sketches from French Guinea and French Guinea
sweet orange oil. Am. Perfumer Essent. Oil Rev. Sept., Oct., Nov.
and Dec.,1941 and Jan. 1942. Reprint 19 pp.
9. GUENTHER, E. The production of oil of limes. Am. Perfumer Essent.
Oil Review. Nov. and Dec. 1942 and Jan., Feb., March and April
1943. Reprint 19 pp.
10. GUENTHER, E. Brazilian sweet orange oil. Food Ind. 16: 898-902,
939-940. 1944.
11. GUENTHER, E. Mandarin and tangerine oils. Food Ind. 16: 979-982,
1021-1022. 1944.
12. GUENTHER, E. The essential oils. Vol. I, 427 pp. 1948. D. Van
Nostrand Co., Inc.
13. GUENTHER, E. Citrus oils and their methods of extraction. Food
Packer. 29: 10, 33-35. 1948.
14. GUENTHER, E., and E. E. LANGENAU. An investigation of the chemical
constituents of distilled lime oil. Jour. Am. Chem. Soc. 65: 959-
963. 1943.
15. HooD, S. C. Relative oil yield of Florida oranges. Ind. Eng. Chem.
8: 709-711. 1916.
16. MARKLEY, K. S., E. K. NELSON, and M. S. SHERMAN. Some wax-like
constituents from expressed oil from the peel of Florida grapefruit.
Jour. Biol. Chem. 118: 433-441. 1937.
17. MOORE, E. L., C. D. ATKINS and E. WIEDERHOLD. A progress report
on Persian limes. Citrus Ind. 29: 6: 5-6. 1948.
18. NELSON, E. K. Florida tangerine oil. Am. Perfumer Essent. Oil
Rev. Sept. 1934.
19. NELSON, E. K., and H. H. MOTTERN. Florida grapefruit oil. Ind.
Eng. Chem. 26: 634-637. 1934.
20. NELSON, E. K., and H. H. MOTTERN. The occurrence of citral in
Florida Valencia orange oil. Jour. Am. Chem. Soc. 56: 1238-1239.
1934.
21. PARRY, E. J. The chemistry of essential oils and artificial perfumes.
2nd Ed., 546 pp. 1908. Scott, Greenwood and Son.







44 Florida Agricultural Experiment Station

22. PIPKIN, W. Method and machine for extracting oil from the peels
of citrus fruit. U. S. Patent No. 2,004,056. June 4, 1935.
23. POORE, H. D. Analyses and composition of California lemon and
orange oils. U. S. Dept. Agr. Tech. Bul. 241: 1-30. 1932.
24. UNITED STATES PHARMACOPOEIA. 13th revision, 957 pp. 1947. Mack
Publishing Company.
25. VON LOESECKE, H. W., and G. N. PULLEY. Physical characteristics of
Florida orange oil produced during 1937-38 season. Fruit Products
Jour. 18: 228-230, 249, 251. 1939.
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foods. Vol. 2, p. 904. 1935. John Wiley and Sons, Inc.









HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






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