L' !AF SA' ~i
EXECUTIVE STAFF BOARD OF CONTROL
John J. Tigert, M. A., LL. D., President H. P. Adair, Chairman, Jacksonville
of the University3 W. M. Palmer. Ocala
Wilmon Newell, D.Sc., Directors R. H. Gore, Fort Lauderdale
Harold Mowry, M. S. A., Asst. Dir., N. B. Jordan, Quincy
Research T. T. Scott, Live Oak
W. M. Fifield, M. S., Asst. Dir., Admin. J. T. Diamond, Secretary, Tallahassee
J. Francis Cooper, M. S. A., Editor3
Clyde Beale, A.B.J., Assistant Editors BRANCH STATIONS
Jefferson Thomas, Assistant Editors NORTH FLORIDA STATION, QUINCY
Ida Keeling Cresap, Librarian J. D. Warner, M.S. Agron. in Charge
Ruby Newhall, Administrative Manager' R. R. Kinkaid, Ph.D., Asso. Plant Path.
K. H. Graham, Business Manager3 R. W. Wallace, B.S., Asso. Agron.
Rachel McQuarrie, Accountant3 Elliott Whitehurst, B.S.A., Assistant An.
MAIN STATION, GAINESVILLE Husbandman4
MAIN STATION, GAINJesse Reeves, Asst. Agron., Tobacco
AGRONOMY W. H. Chapman M.S., Asst. Agron.
W. E. Stokes, M.S., Agronomist'
W. A. Leukel, Ph.D., Agronomists CITRUS STATION, LAKE ALFRED
Fred H. Hull, Ph.D., Agronomist A. F. Camp, Ph.D.. Horticulturist in Chg.
G. E. Ritchey, M.S., Associate2 Chas. K. Clark, Ph.D., Chemist
W. A. Carver, Ph. D., Associate V. C. Jamison, Ph.D., Soils Chemist
Roy E. Blaser, M.S.. Associate B. R. Fudge, Ph.D., Associate Chemist
G. B. Killinger, Ph.D., Associate W. L. Thompson, B.S., Associate Ento.
John P. Camp, M.S., Assistant F. F. Cowart, Ph.D., Asso. Horticulturist
Fred A. Clark, B.S.A., Assistant W. W. Lawless, B.S., Asst. Horticulturist
R. K. Voorhees, Ph.D., Asso. Plant Path.
ANIMAL INDUSTRY T. W. Young, Ph.D., Asso. Hort., Coastal
A. L. Shealy, D.V.M., An. Industrialist, Ph.D., Asso. Hort., Coastal
R. B. Becker, Ph.D., Dairy Husbandman' EVERGLADES STA., BELLE GLADE
E. L. Fouts, Ph.D., Dairy Technologist' J. R. Neller, Ph.D., Biochemist in Chg.
D. A. Sanders, D.V.M., Veterinarian J. W. Wilson, Sc.D., Entomologist
M. W. Emmel, D.V.M., Veterinarian' F. D. Stevens, B.S., Sugarcane Agron.
L. E. Swanson, D.V.M., Parasitologist Thomas Bregger, Ph.D., Sugarcane
N. R. Mehrhof, M.Agr., Poultry Husb.' Physiologist
W. M. Neal, Ph.D., Asso. in An. Nutrition G. R. Townsend, Ph.D., Plant Pathologist
T. R. Freeman, Ph.D., Asso. in Dairy Mfg. R. W. Kidder, M.S., Asst. An. Husb.
R. S. Glascock, Ph.D., Asso. An. Husb. W. T. Forsee, Ph.D., Asso. Chemist
D. J. Smith, B.S.A., Asst An. Husb.' B. S. Clayton, B.S.C.E., Drainage Eng.2
P. T. Dix Arnold, M.S.A., Asst. Dairy F. S. Andrews, Ph. D., Asso Truck Hort.4
Husbandman' Roy A. Bair, Ph.D., Asst. Agron.
L. L. Rusoff, Ph.D., Asst. in An. Nutr.'
L. E. Mull, M.S., Asst. in Dairy Tech. SUB-TROPICAL STA., HOMESTEAD
O. K. Moore, M.S., Asst. Poultry Husb. Geo. D. Ruehle, Ph.D., Plant Pathologist
ECONOMICS, AGRICULTURE in Charge
ECONO CS, AGRI URE S. J. Lynch., B.S.A., Asst. Horticulturist
C. V. Noble, Ph.D., Agr. Economist' E. M. Andersen, Ph.D., Asst. Hort.
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Associate W. CENT. FLA. STA., BROOKSVILLE
Max E. Brunk, M.S., Assistant W. F. Ward, M.S., Asst. An. Husband-
ECONOMICS, HOME man in Charge'
Ouida D. Abbott, Ph.D., Home Econ.' RANGE CATTLE STA., ONA
Ruth Overstreet, R.N., Assistant W. G. Kirk, Ph. D. An. Husb. in Charge
R. B. French, Ph.D., Asso. Chemist E. M. Hodges, Ph.D., Asso. Agron.
ENTOMOLOGY Gilbert A. Tucker, B.S.A. Asst. An. Husb.
J. R. Watson, A.M., Entomologist'
A. N. Tissot, Ph.D., Associate FIELD STATIONS
H. E. Bratley, M.S.A., Assistant Leesburg
HORTICULTURE M. N. Walker, Ph.D., Plant Pathologist
G. H. Blackmon, M.S.A., Horticulturist' in Charge
F. L. Stahl, Ph.D., Associate Hort. K. W. Loucks, M.S., Asst. Plant Path.
F. S. Jamison, Ph.D., Truck Hort.8
R. J. Wilmot, M.S.A., Asst. Hort. Plant City
R. D. Dickey, M.S.A., Asst. Horticulturist A. N. Brooks, Ph.D., Plant Pathologist
J. Carlton Cain, B.S.A., Asst. Hort.' Hastings
Victor F. Nettles, M.S.A., Asst. Hort.' A. H. Eddins, Ph.D., Plant Pathologist
F. S. Lagasse, Ph.D., Asso. Horticulturist' E. N. McCubbin, Ph.D., Asso. Truck
H. M. Sell, Ph.D., Asso. Horticulturist' Horticulturist
PLANT PATHOLOGY Monticello
W. B. Tisdale, Ph.D., Plant Pathologist',' A. M. Phillips, B.S., Asst. Entomologists
George F. Weber, Ph.D., Plant Path.'
L. O. Gratz, Ph.D., Plant Pathologist Bradenton
Erdman West, M.S., Mycologist Jos. R. Beckenbach, Ph.D.. Truck Horti-
Lillian E. Arnold, M.S., Asst. Botanist culturist in Charge
SOS David G. Kelbert, Asst. Plant Pathologist
R. V. Allison, Ph.D., Chemistl,' Sanford
Gaylord M. Volk, M.S., Chemist R. W. Ruprecht, Ph.D., Chemist in
F. B. Smith, Ph.D., Microbiologists Charge, Celery Investigations
C. E. Bell, Ph.D., Associate Chemist W. B. Shippy, Ph.D., Asso. Plant Path.
J. Russell Henderson, M.S.A., Associates Lakeland
L. H. Rogers, Ph.D., Asso. Biochemist E. S. Ellison, Meteorologists
H. W. Winsor, B.S.A., Assistant Chemist
Richard A. Carrigan, B.S., Asst. Chemist 'Head of Department
Geo. D. Thornton, M.S., Asst. Chemist 'In cooperation with U. S.
R. E. Caldwell, M.S.A., Soil Surveyor sCooperative, other divisions, U. of F.
Olaf C. Olson, B.S., Soil Surveyor O0n leave for military service.
Introduction .... .. . 5
Previous Wrapper Investigations _------- ----------------- 7
Properties of Pliofilm-- ------------------- ---------------- 9
Explanation of Terms Used -------------------------------- 12
Citrus Fruits ------------- -------------.--------------- 13
Round Oranges ---------------------------------------- 15
Hamlin ---------- -------------------------------- 15
Pineapple -------------------------------------------- 16
Valencia ---------------------------------- 20
Mandarin Oranges ------------ 25
Tangerines ------------------------- 25
Satsumas .-------------------------- 28
Temples .-------------.--------.. ---------------- 29
Grapefruit ------------------- ..---------------------------------. 32
Duncan ------------- -------------- ---.---....-.--------3.... 32
Marsh Seedless, Silver Cluster and Singletary Varieties .-- 36
Limes --------------_...... ----..-------..--.. .----------- 36
Persian ------------------------- ------.---.-------- 36
Key ....----------------------- -..-.. --------------------- 37
Kumquats -.__---------..._._-.-_-__.....------------------ 37
Pliopeal Oranges --------------....... ----... ---------...- 38
Commercial Application ----.--- -----------------------------------.. 41
Discussion .. -----------------------------_--__-..... ..----..---..-- 46
Other Florida Fruits -----. -------- --------.-------------- 47
Persimmons ..-------------------... -----.----------- 47
Mangos .---------------.-------- ------... ------------- 49
Peaches ---------------------------------------------- 51
Avocados -----------------.-------------..------ 55
Preliminary Vegetable Investigations ------.---------._ ------- 58
Cabbage --------- --------------------------------.. 60
Lettuce .-------------------------------.-.... -- ----. 62
Celery .-----------------------..----------.------- 65
Peppers .---------------------------------------------_-------- 69
Cucumbers .-------------------.------_---------- ------ 73
Eggplants ..---------------------------------------. 73
Tomatoes ------------ ------------------------------- 75
Onions .------------------------------------.------ 80
Corn .-------------------------------. ------------ 81
Cauliflower --------------------------------------- 86
Brussels Sprouts -------------.------------------------- 86
Broccoli ----_------------------------------------- 86
Discussion ------------.----------------------------- 87
Summary __---------------._-------------------------- 88
Citrus Fruits .---------------.-----------------------. 88
Other Florida Fruits -----............---------- --- -- ---- ----- 89
Vegetables ----- --------------------------------_ 90
Literature Cited ----------------------------- ----------.. 91
Fig. 1.-Florida fruits and vegetables such as these were preserved
in fresh state over longer periods with pliofilm wrappers and plioseal in
the experiments reported herewith.
Gift of Issuing offlo
PLIOFILM IN THE PRESERVATION OF
FLORIDA FRUITS AND VEGETABLES
By ARTHUR L. STAHL AND PAUL J. VAUGHAN1
A growing competition with canned, frozen, and concen-
trated food products emphasizes the importance of improved
methods of wrapping and packing fresh Florida fruits and vege-
tables in order that they may reach the markets in the best con-
dition and as nearly as possible like the freshly harvested pro-
Vitamins, mineral elements and other substances essential to
the growth and health of the human body are found in greatest
abundance in fresh food products. It is therefore of important-
ance to keep food products as long as possible in the fresh con-
dition. In the marketing of Florida produce long distance trans-
portation is necessary and any economical means which can be
found to keep fruit and vegetables in a fresh state for longer per-
iods of time is of great value.
The causes of deterioration after harvesting are both path-
ological and physiological. Pathological deterioration is caused
by fungi and bacteria attacking the produce and causing subse-
quent decay. This may be reduced by either the prevention or
inhibition of growth of the organism. Physiological deterioration,
which is often a combination of many things intimately related to
the catabolism of the fruit or vegetable, can be reduced by slow-
ing down the respiration and transpiration (moisture loss). Both
types of deterioration are commonly reduced by surface treat-
ments, wrapping, and refrigeration. This investigation deals
primarily with wrapping.
A fruit or vegetable is a living plant even after it is
harvested. It is capable of carrying on the life processes, to a
certain extent, as it did before harvest. In fact, its catabolic
activities are even greater because it must maintain its life en-
tirely on the food products stored within itself (sugars, acids,
proteins, fats, etc.). Hence the metabolic activity is entirely a
destructive one-catabolism. This includes respiration, which is
the chemical process of breaking down these organic food ma-
terials with a release of energy which is used to maintain life;
transpiration, which is the elimination of the water evolved
6 Florida Agricultural Experiment Station
during these respiratory reactions; and the other physical and
chemical changes taking place during the destructive life pro-
cess. The fruit or vegetable' is of greatest value when it contains
the most food elements, yet this process of catabolism destroys
much of the food value. The object, then, is to slow down this
process as much as possible without stopping it altogether, thus
preventing loss of food value, and still maintaining the fresh con-
dition of produce as long as possible.
Oxygen is necessary for normal respiration and this cannot
be cut off entirely because abnormal (anaerobic) respiration then
takes place, with the production of toxic by-products that en-
danger the life of the fruit or vegetable. Also, the by-products
of aerobic (normal) respiration must be eliminated. These norm-
ally pass off into the surrounding atmosphere in the form of
gases and vapers as indicated by loss in weight, size and qual-
ity. Since the oxygen necessary for normal respiration comes
from the atmosphere, and the wastes, or by-products, are ex-
pelled into the atmosphere, it is readily seen that, in a small
closed system, such as an air-tight container, the atmosphere
would soon become contaminated with waste products and de-
ficient in the life-maintaining elements (18)'. This condition is
unfavorable in maintaining proper life balance and will produce
stale tastes and physiological breakdown. It is readily apparent
that the ideal fruit and vegetable wrapper to keep the fruit in a
perfect physiological state should allow for a diffusion of respira-
tory gases through the film and yet be very efficient in the reten-
tion of moisture.
Many wrappers have been tried for citrus fruits during the
past several years. A report of the reaction of these when used
on commercial varieties of citrus was given in Florida Agricul-
tural Experiment Station Bulletin 304. Since that time as new
products which could be used as wrappers were placed on the
market they have been tested, not only on citrus but on other
Florida fruits and vegetables as well. Trials were made on their
use under cold storage conditions, as well as under conditions
prevailing at the time of the commercial handling of the crop.
A study of the physical properties of pliofilm indicated the
possibility of its use as an ideal produce wrapper, since this ma-
terial would allow for the passage of respiratory gases while re-
taining moisture (18).
"Italic figures in parentheses refer to "Literature Cited".
Pliofilm in the Preservation of Florida Fruits and Vegetables 7
Results of preliminary trials of pliofilm as a fruit and vege-
table wrapper were so outstanding that additional investigations
have been carried out on many varieties of fruits and vegetables
during the past three years (1938-1941). Various types, gauges
and colors of pliofilm were used on many varieties of citrus, other
fruits, and vegetables held at ordinary temperatures and in cold
storage. This bulletin is a report of these investigations.
PREVIOUS WRAPPER INVESTIGATIONS
Paper was the first sheet material used in wrapping and was
apparently used for packing and wrapping fruit as early as 1856,
when its use was reported by Hovey's Garden Magazine (1). In
1859 paper was used as a wrapper on grapes (2) and, in 1879,
oranges shipped from Australia to England were wrapped with
paper, but the paper proved inferior to a sawdust pack (3). It
was used for packaging figs and peaches in 1879 (9). After this
period the wrapping of fruit was more commonly employed but
the use of wrappers for protection of vegetables came somewhat
later, their use for cucumbers and tomatoes being reported in
At first plain tissue and other cheap grades of paper were
used almost entirely. The main object was to decrease loss in
weight. Hendrickson (13) found that tissue wrappers were un-
satisfactory as they prevented little moisture loss and became
entirely soaked within a few hours after removal from cold
storage, causing a soggy condition of the pack. Tissue-wrapped
citrus fruit developed pitting, as did also fruit not wrapped.
Later, better grades of paper were used and it was learned
that impregnating the paper with oils and waxes made them
more moistureproof and had some value in reducing scald and
other physiological disorders. The value of wrapping apples in
oiled paper was shown by Kidd and West (14) using scald-suscept-
ible varieties. After four and one-half months in ordinary stor-
age, fruits in oiled paper remained about 48 percent sound as
compared with 5 percent for waxed paper and 3 percent for un-
wrapped fruit. Brooks, Cooley and Fisher (6) found that un-
oiled wrappers had no effect in controlling apple scald, and
that, while paraffined wraps caused considerable reduction in
the amount of scald, they proved far inferior to oiled wraps.
Many types of oiled wrappers were tested and most of them
proved efficient in scald control.
8 Florida Agricultural Experiment Station
Tindale (23) showed that Washington Navel oranges, when
wrapped in the better wrappers, remained in a firmer condition
and the formation of mold "nesting" in the packed boxes was
Powell and Fulton (16) experimented with unprinted news-
paper, tissue, parchment, and waxed paper wrappers on apples,
and found that the fruit wrapper retarded the ripening of the
fruit, preserved its brighter color, checked transpiration, pro-
tected it from bruising, and prevented the spread of fungus spores
from decayed to perfect fruit. Parchment and waxed wrappers
were found to be slightly more efficient than the others. Mold
developed freely on the parchment paper at all temperatures.
Impregnation of the wrapper with certain chemicals to re-
duce or inhibit fungal growth has been used by some investi-
gators. Tomkins (24) found that certain types of rotting can be
controlled by the use of iodized wraps but the greatest caution
must be exercised before the principle can be applied to fruit
handled under commercial conditions. The nature of the specific
fungi requires a knowledge of their pathogenicity and the effect
of iodine on the fruit also must be clearly understood in ad-
vance. Rotting of grapes, tomatoes, apples, plums, and peaches
has been reduced by storage in iodized wraps. Appearance and
ripening of some varieties of these fruits and vegetables, how-
ever, are affected adversely by this treatment.
Cooley and Crenshaw (10) found that Botrytis rot could be
controlled in pears by the use of oiled or plain wrappers im-
pregnated with 25% solution of copper sulphate, the dry wrapper
carrying about 1.4% of its dry weight in metallic copper.
The influence of wrappers on succulence, flavor, color, and
undesirable contaminations of foodstuffs, varies greatly with the
materials used. Very little is known concerning the effect of
various wrappers on the quality of horticultural products. Sando
(17) found that tomatoes ripened off the vine with diminished
ventilation due to paper wrappers had a high acid content and a
low soluble carbohydrate (sugars) content, while well ventilated
tomatoes contained relatively more sugar and less acid and
possessed a flavor more nearly like that of fruits ripened on
the vines. He also states that, although the reaction of wrapped
tomatoes was decidedly acid, the general flavor was insipid. He
concludes that lack of ventilation retards ripening. Duggar (11)
states that the lack of oxygen inhibits the development of the
red color of tomatoes. McKay, Fisher and Nelson (15) found that
Pliofilm in the Preservation of Florida Fruits and Vegetables 9
wrappers interfere with cooling of cantaloupes placed under re-
frigeration and that wrappers, by retaining the moisture con-
densed on the melons after their removal from refrigeration,
favor the spread of disease. Brown (7) observed that waxed
papers reduced moisture loss from certain vegetables but that
decay was greater. He found also that paper wrappers had some
cushioning value which helped protect perishable products from
mechanical injury. Plain, oiled, and waxed paper wrappers
had no effect upon preventing the decrease of sugars in corn or
peas. No increase in acidity either as pH or titratable acidity
could be detected in tomatoes as a result of wrappers.
In the past several years many types of moistureproof wrap-
pers have been placed on the market, among which are the
metal foils, cellulose acetate products and rubber hydrochlorides.
The last two are transparent films. Several years ago Stahl and
Fifield (21) showed the superiority of moistureproof wrappers
for the preservation of citrus fruits in storage. Many wrap-
pers were used at various temperatures on a large number of
the commercial citrus varieties.
Experiments conducted by the Texas Agricultural Experi-
ment Station (26) have resulted in the development of practical
methods to preserve weight, color, turgidity, texture, flavor ahd
palatability of vegetables in moistureproof cellulose films.
Pliofilm is being used on many manufactured food products
such as cheese, prepared meats, soup mixtures and candies. The
reaction of these products in the film has been reported in sev-
eral trade journals (8) (12). Little investigational work has been
published on pliofilm used on fruits and vegetables. Brief reports
of preliminary investigations on Florida fruits and vegetables are
given in the 1939 and 1940 annual reports of the Florida Agri-
cultural Experiment Station (19).
PROPERTIES OF PLIOFILM
Pliofilm is a synthetic plastic containing rubber hydrochlo-
ride as its principal base. It is transparent, tasteless, odorless,
tough, durable, thermoplastic, and moistureproof, yet permeable
to carbon dioxide gas (22).
Rubber, one of the basic raw materials used in the manu-
facture of pliofilm, seems to give to this product two important
physical properties desirable in a fruit and vegetable wrapper.
These are moistureproofness and high permeability to carbon
dioxide gas (25).
10 Florida Agricultural Experiment Station
Pliofilm is inherently moistureproof. This is a property of
the rubber hydrochloride film itself and is not obtained by a
coating or impregnation with another material that might flake or
peel off. In its resistance to the passage of moisture vapor,
pliofilm compares favorably with equal thicknesses of other mois-
tureproof material now on the market.
Carbon dioxide gas diffuses through pliofilm 10 to 20 times
as fast as does ordinary air.
Pliofilm is quite resistant to punctures, tears, and abrasions
and is pliable at ordinary temperatures. This ability to absorb
the shocks of processing, transportation and marketing is essen-
tial in packaging Florida produce which often goes to distant
Pliofilm is not attacked by insects or vermin, and molds will
not grow on its surface, nor can their spores or mycelia pass
through the film. The transparency of pliofilm permits the
contents of the sealed package to be seen without being opened,
thus preventing outside contamination during the marketing
Pliofilm has dimensional stability through the entire hu-
midity range at ordinary temperatures but becomes thermoplas-
Fig. 2.-Laboratory model pliosealing machine, showing the plio-
film clamped in the frame and the heating element raised.
Pliofilm in the Preservation of Florida Fruits and Vegetables 11
Fig. 3.-The heating element is lowered to contact the pliofilm sheet.
tic at a temperature of 325' F. This latter feature allows it to
be heat-sealed in a welded bond, and also permits a novel type of
packaging known as the plioseal or stretch-wrap. In the latter
operation the film is clamped firmly in a frame (Fig. 2). The
heating element is then lowered (Fig. 3) and allowed to remain
in contact with the pliofilm for one or two seconds. The heat-
ing element is then returned to the original position and the
object to be wrapped is thrust firmly into the plastic film to a
depth slightly greater than the diameter of the fruit or vege-
table (Fig. 4). The fruit is then grasped beneath the frame with
the left hand and pushed upward with an accompanying half-
twist on the horizontal axis. This latter operation brings the
edges of the stretched pocket together in the form of a welded
seal. The seal is then trimmed, another section of film is clamp-
ed into the frame and the process repeated. This type of pack-
age permits the wrapping of irregular objects without seams or
folds, since the film always assumes the shape of the object. Dur-
ing this operation the pliofilm does not become sticky and does
not adhere to the object but rather takes the form of a trans-
parent protective skin.
The thickness of pliofilm is designated by guage. For ex-
ample, 120 guage is approximately .0012 inch thick and 80 gauge
is .0008 inch in thickness. Thinner gauges such as those used in
most of the following experiments are termed tensilite. Tensilite
pliofilm is manufactured by stretching the film as it passes over
heated rolls. Thus from heavier gauges 40 and 20 gauges (.0004
and .0002 inch thickness) are manufactured, retaining the qualities
of utensilized pliofilm but proving an economy of material.
12 Florida Agricultural Experiment Station
Fig. 4.-The object to be wrapped is thrust into the plastic film and
twisted, making the seal.
It has been found that small amounts of a plasticizer included
in pliofilm make it more durable. Films of this type are desig-
nated as N1, N2, N3, etc., indicating varying amounts of plasticiz-
er. Unless stated otherwise, all the pliofilm used in these ex-
periments contains no plasticizer.
EXPLANATION OF TERMS USED
Plioseal.-The term used to describe the type of wrapping in
which the previously-heated pliofilm assumes the form of the
wrapped object, as described above. Eighty-gauge pliofilm was
used in the machine, and the final thickness of the plioseal
Pliopeel.-This is the plioseal wrapper applied to peeled
fruits, enclosing the fruit in a sealed pliofilm covering.
Sheet Wrapper.-A square sheet commonly used to wrap
produce individually. The object is placed in the center of the
sheet and the edges are brought together and twisted, forming
Pliofilm Bags.-These are fabricated bags, usually made of
120-gauge material with heat-sealed seams.
Pliofilm in the Preservation of Florida Fruits and Vegetables 13
Unwrapped, Control Samples.-These are terms used to
designate produce obtained from the same source and subjected
to the same conditions but not wrapped. Thus, the effect of
wrapping may be measured by comparison of fruits or vege-
tables wrapped and not wrapped.
Tissue Wrapped.-This is the common paper ordinarily used
for wrapping citrus fruits in Florida. It is designated herein as
Unmarketable.-The state or condition of produce rendered
unsalable by pathological or physiological deterioration, as
judged by three or more persons.
The principal function of a fruit wrapper is to prevent deter-
ioration and dehydration of the fruit and thus preserve its orig-
inal quality and attractiveness from the time of packing until
consumption. This time interval varies, depending on the method
of transportation, distance to market area, volume of sales of the
retail store and the rate of consumption. In addition, the fruit
may be stored for a time to await a better market price.
The protection of fruit from dehydration is of great import-
ance, particularly in Northern market areas, which have com-
paratively low humidities during the Florida marketing season.
This is especially true for small retail stores, where it is often
necessary to keep the fruit on the display counters for a consider-
During transportation the wrapper is of value in preventing
bruising and abrasion between the individual fruits and between
the fruit and box. If there is damage to the fruit during packing
or transit, and mold infection occurs, the wrapper should prevent
the spread of spores and mycelia from the decayed fruit to oth-
ers and in this manner prevent "nesting".
The wrapper has an important function in preserving the
original quality and freshness of the fruit during and after re-
moval from storage. There are two general applications of stor-
age in the marketing scheme of Florida citrus. Short-term stor-
age may be used to advantage when oversupply in a particular
market area has caused a temporary depression in prices. Also,
it is often profitable to store part of the crop of certain varieties
of citrus such as the Mandarin oranges past their ordinary har-
vest time for more profitable late season markets. The longer
14 Florida Agricultural Experiment Station
storage period may be used to extend the marketing season of the
All of the above-mentioned factors were considered in plan-
ning and conducting the investigations on the use of pliofilm as a
The citrus fruits used in these experiments were obtained
from the groves of the Experiment Stations at Gainesville and
Lake Alfred; Crosby-Wartmann Groves, Inc., Citra; Swan Groves,
Winter Haven; and Wirt Groves, Babson Park. Fruit was obtained
also from the Polk Packing Association, Winter Haven; Florence
Villa Growers' Association, Florence Villa; American Fruit
Growers, Inc., Maitland; Waverly Growers' Cooperative, Waver-
ly; J. M. Ingram Packing Co., Tampa; Theodore Strawn, Inc.,
DeLeon Springs; Purpura Bros., Inc., Citra. An effort was made
to wrap the fruit as soon as possible after picking. At no time
was the interval between picking and wrapping more than 12
hours and, in the majority of cases it was less than six hours.
The majority of fruit was not treated in any way except the
washing, grading, and sizing practised in the ordinary packing-
house. In a number of cases both waxed and unwaxed fruits
The fruits were placed under observation in the Horticul-
tural Laboratories and the Refrigeration Plant at the Agricul-
tural Experiment Station in Gainesville, which have been de-
scribed fully in Bulletin 303 (20). Temperatures of 370 F. and
420 F. were used to approximate the conditions of refrigerated
transit and storage. The control temperature of 700 F. was chos-
en because it approximates the average for retail stores at the time
Florida fruits are placed on the market. Experimental holding
rooms of temperatures of 37' F. and 420 F. were maintained at a
relative humidity of 80 percent; fruit held at 700 F. was kept at
varying relative humidities of from 50 to 70 percent. Some fruits
also were held at room temperatures which averaged 700 F. to
80 F. during winter and 700 F to 900 F. during summer.
Sufficient numbers of samples were used in all varieties to
prevent individual variation appreciably affecting the results.
The fruit was wrapped at ordinary room temperatures and
placed on slatted shelves at the various storage temperatures in
such a position as to give free circulation of air, or packed in
either standard (nailed) or Bruce (wire-bound) boxes using the
commercial methods of packing. The individual fruits were
weighed to a tenth of a gram and the packed boxes to /s pound
Pliofiim in the Preservation of Florida Fruits and Vegetables 15
accuracy. Unless otherwise specified, the amount of fruit placed
on shelves and weighed individually to obtain an average per-
centage loss in weight was never less than 75 fruit for each con-
dition, 100 being the number most generally used. Likewise,
unless otherwise specified, the number of packed boxes used for
each condition was never less than five and in most cases 10.
Figures in the tables and graphs are averages of fruit weighed
individually from shelves, unless it is stated specifically that they
are weights of commercial packs. At regular intervals fruit on
the shelves and in the commercial boxes were examined for
shriveling, color, quality and flavor. Several varieties of round
oranges, Mandarin oranges and grapefruit were used, including
early, mid-season and late varieties of round oranges and both
20c seedy and seed-
S 2 3 1 less grapefruit.
Results of the ex-.
HAML ORANGES periment are re-
corded as numer-
ical data, supple-
15 mented by
0 ges.-To determ-
_/ ine the effect of
40-gauge pl io -
fil m wrappers,
4 fully-colored and
5 oranges produced
o n sour-orange
6 placed at two
peratures, 3 7
0 2 4T 6 8 10 12 1
Time in Storage (weeks and 700 F., and at
Fig. 5.-Percentage weight loss of Hamlin ordinary room
oranges held at three temperatures, wrapped in
40-guage pliofilm and unwrapped. At room tem- temperature (70'
perature (70-80 F.) 1, no wrapper and 4, wrap- F. 800 F.)
ped; at 700 F. 2, no wrapper and 5, wrapped; and Ta 1 s
at 370 F. 3, no wrapper and 6, wrapped. Table 1 shows
16 Florida Agricultural Experiment Station
the marked effect of the pliofilm wrapper in preventing rapid
weight loss shown by unwrapped fruit at all temperatures. The
rate at which the unwrapped oranges lost weight changed only
slightly during the course of the experiment.
The rapid weight loss of unwrapped fruit was accompanied
by a marked deterioration in its freshness and appearance. The
peel and buttons became shriveled and dried. The weight loss
was accompanied by a decrease in size of the fruit. These effects
were more rapid at room temperature, making the unwrapped
fruit commercially unmarketable after two weeks. At the lower
temperatures the unwrapped oranges did not lose weight as
quickly, but soon became badly pitted and showed severe stem-
Oranges subjected to the same conditions but wrapped with
40-gauge pliofilm showed a slight weight loss which averaged
less than 1/10 that of the unwrapped fruit for the first two
months (Fig. 5). Taste and appearance of the pliofilm-wrapped
fruit did not change appreciably during the experiment. The
orange color of the fresh fruit was preserved by the pliofilm
wrappers and in addition the fresh green color of the buttons was
Depreciation in quality of fruit after removal from storage
at 370 F. was considerably greater in unwrapped fruit, due main-
ly to increased dehydration. There was no significant difference
in amount of decay in the wrapped and unwrapped fruit at the
lower temperature, but at room temperature the percentage of
rots in unwrapped fruit was higher. Rind pitting and browning
were controlled successfully by pliofilm wrappers at all temper-
atures, but were severe in the fruit not wrapped, especially at the
lower temperatures. In all cases the color and freshness of the
buttons were preserved by the pliofilm wrappers.
Results of these experiments indicate clearly that pliofilm-
wrapped Hamlin oranges could be placed on distant markets in a
much better condition than is now possible.
During the season of 1941 the experiment with Hamlin
oranges was repeated, using 20-gauge sheet wrappers and plio-
sealing (stretch-wrapping) instead of 40-gauge sheet wrappers.
Both types of wrapping gave results very similar to those of the
40-gauge wrapper. The pliosealed oranges showed a more at-
tractive luster furnished by the skin-tight, transparent pliofilm.
Pineapple Oranges.-The investigation on pliofilm-wrapped
Pineapple oranges covered a period of three seasons (1938-1941).
TABLE 1.-EFFECT OF PLIOFILM WRAPPERS ON THE PERCENTAGE Loss IN WEIGIIT OF HAMLIN ORANGES AT 370 F., 70' F. AND AT RooM
Percentage Loss in Weight After (Weeks)
Temperature Wrapper 2 3 5 7 9 10 11 12 13 15 L
40-gauge sheet 0.09 0.19 0.32 0.71 0.84 0.95 1.30 1.90 2.32 -
37" F. None (Control) 3.58 4.92 6.81 9.00 10.74* 11.68 15.19 19.20 22.03 -
40-gauge sheet 0.44 0.95 2.02 3.25 3.43 4.44 --- 5.18 -
70 F. None (Control) 5.08 6.79 14.66 20.08 21.57 27.63 32.90 1
40-gauge sheet 0.84 1.36 1.88 2.50 3.75 4.06 -- 5.37 -- 6.45
Room Temperature None (Control) 8.09 9.46* 13.84 17.26 23.86 25.74 30.10 --- 34.60
18 Florida Agricultural Experiment Station
During this time 40-gauge sheet wrappers were used on large
quantities of Pineapple oranges, which were placed on shelves or
packed in boxes and held at different temperatures and under
various conditions. Losses in weight and observations as to
quality, texture, taste and percent decay were recorded at inter-
vals. Fruit was used from both high pine and hammock soils.
Fig. 6.-Pineapple oranges after four months' storage at room tem-
perature. Fruit at left wrapped in pliofilm, that at right unwrapped.
Pliofilm in the Preservation of Florida Fruits and Vegetables 19
Fruit on the high pine soil was produced on rough lemon root-
stock and that on hammock soil was grown on sour orange root-
stock. No difference in behavior of fruit wrapped in pliofilm
could be attributed to rootstock influence. Since the results were
practically the same for the three seasons and for fruit from both
rootstocks, only the results for the 1940-41 season with Pineapple
oranges grown on sour orange stock will be presented here.
Pineapple oranges were picked January 22, 1941, and placed
under observation at two storage temperatures, 370 F., and 42
F., and at room temperature (700-80 F.) with no treatment other
than wrapping in 40-gauge pliofilm. In addition, several boxes
of fruit wrapped in 40-gauge pliofilm were placed in storage at
370 F. for comparison with control boxes not wrapped as a check
20 on the perform-
ance of the wrap-
per under com-
PINEAPPLE ORANGES mercial c o n d i-
tions of packing.
Table 2 shows
15 t the percentage
weight loss of the
2 oranges at tem-
peratures of 37
/F., 42 F. and at
-/ room tempera-
/ture (700-80 F.).
Under all con-
S editions the weight
loss of wrapped
fruit was small
i n comparison
with that of fruit
n ot wrapped.
B The original ap-
0 2 4 8 10 12 14 pearance and
Time in Storage (weeks) taste were well
Fig. 7.-Percentage weight loss of Pineapple preserved during
oranges held at three temperatures, wrapped in the course of the
40-gauge pliofilm and unwrapped. At room tem-
peratures (70-90 F.) 1, unwrapped and 4, wrap- experiment at all
ped; at 42 F. 2, unwrapped and 5, wrapped; and temperatures,
at 37 F. 3, unwrapped and 6, wrapped.
20 Florida Agricultural Experiment Station
and a noteworthy feature of the pliofilm wrapper was its per-
formance at room temperature. Original color and texture of
oranges wrapped in pliofilm at room temperature were un-
changed after two months, while the appearance of unwrapped
controls showed effects of the loss in weight within a short time
by a shriveled and leathery texture of the peel and loss of
juice (Fig. 6). This degeneration of appearance was soon fol-
lowed by a loss of initial flavor and taste, and, after three weeks,
the unwrapped fruit was altogether unmarketable at this tem-
perature. At this point the fruit protected by 40-gauge pliofilm
had lost only 1.25 percent of its total weight and was unchanged
in appearance, quality and taste (Fig. 7).
The fruit at the higher relative humidity and low controlled
temperatures showed the same effects, after a longer time inter-
val. In addition to the drying effects, the fruit at the lower
temperatures showed rind pitting when not protected by the
wrapper. At 370F. and 420 F. rind pitting appeared after three
to four weeks in the unwrapped control samples, in addition to
the severe drying symptoms observed after four weeks.
During the entire storage of 17 weeks pliofilm-covered fruit
at the lower temperatures did not show pitting, drying or change
in taste. This was quite remarkable in that they did not have.
"storage taste" and pitting commonly associated with fruit ordi-
narily stored for this length of time.
Results for all three seasons show very definitely the ad-
vantages of wrapping Pineapple oranges in pliofilm. This plio-
film protection is of advantage, not only in permitting the fruit
to be held over short periods in storage for a better price when
the market is oversupplied, but also in the regular marketing
channels by permitting the fruit to remain in good condition for
a longer time on the retail stand, or in transit to more distant
Valencia Oranges.-The investigations with Valencia oranges,
as with Pineapple oranges, were conducted over a period of three
seasons (1938-1941). During the first two seasons the fruit was
wrapped in 40-gauge sheet wrappers and held at temperatures
of 370 F., 420 F. and 70 F. The Valencia oranges the first season
were obtained from the Citrus Experiment Station and were
grown on rough lemon rootstock, while those used the second and
third seasons came from Citra and were grown on sour orange
stock. No differences were noted between the storage reactions
of pliofilm-wrapped oranges grown on different rootstocks.
TABLE 2.-EFFECTS OF PLIOFILM WRAPPERS ON THE PERCENTAGE Loss IN WEIGHT OF PINEAPPLE ORANGES AT 37 F., 420 F., AND ROOM
TEMPERATURE (700-80 F.).
Percentage Loss in Weight After Weeks ____
Temperature 1 2 4 7 9 11 13 16 8 161/2 17
40-gauge sheet 0.19 0.25 0.42 0.56 0.69 0.88 1.05 1.30 P 4 2.10 2.90
370 F. None (Control) 1.21 1.94 3.39 6.02 7.74 9.19 10.98 13.40 o 16.70 20.30
42* F. 40-gauge sheet 0.19 0.39 0.69 0.87 1.05 1.28 1.49 1.72 I 2.30 2.89
None (Control) 1.43 2.44 4.66 6.71 8.28 10.02 12.73 14.90 E 18.40 21.10
Room 40-gauge sheet 0.37 0.93 1.60 2.67 3.73 4.55 5.89 7.80 --
Temperature None (Control) 2.94 6.06 10.72 19.60 26.04 31.51 37.86 39.00 ....
TABLE 3.-EFFECT OF VARIOUS TYPES OF PLIOFILM WRAPPERS ON THE Loss IN WEIGHT OF VALENCIA ORANGES AT 370 F. AND 700 F.
S W Percentage Loss in Weight After Weeks
"1 2 3 4 6 8 10 12 14 16 18 20
20-gauge sheet 0.06 0.19 0.30 0.40 0.61 0.84 1.08 1.26 1.47 1.77 1.92 2.12
40-gauge sheet 0.07 0.09 0.14 0.21 0.34 0.48 0.59 0.73 0.85 0.99 1.06 1.13
37 F. Plioseal
(Cold Storage) (Stretch-wrap) 0.08 0.17 0.26 0.31 0.52 0.66 0.83 1.08 1.21 1.45 1.71 1.96
None (Control) 1.34 2.65 3.84 5.01 7.45 9.40 12.12 13.87 16.06 18.00 20.08 22.10
20-gauge sheet 0.75 1.22 1.78 2.08-- --... .. .... ..
40-gauge sheet 0.62 1.14 1.54 1.93 ... .... .... .. .
70 F. Plioseal
(Retail stand) (Stretch-wrap) 0.70 1.21 1.71 2.07
None (Control) 3.84 6.52 9.37 12.21
22 Florida Agricultural Experiment Station
Additional types, gauges and colors of pliofilm wrappers were
used in 1941. The loss in weight and the condition of the fruit as
to quality, texture and taste were recorded at regular intervals
for all three seasons. Since the results of the investigations on
Valencias were so nearly the same for the three seasons only
the work of the 1940-41 season is presented.
Valencia oranges picked April 18 were washed, wrapped
with pliofilm and placed under observation at 37' F. and 70 F.
Three types of wrapping were used-40-gauge sheet wrap, 20-
gauge sheet wrap and plioseal-and the reaction of the fruit in
these wrappers was compared with unwrapped controls sub-
jected to the same conditions. Records on loss of quality and
weight were taken at regular intervals on the fruit on shelves
as well as that packed in standard and Bruce boxes.
Table 3 shows the effect of three types of pliofilm wrappers
in preventing loss of weight at 370 F. (cold storage) and 700 F.
(retail stand). A comparison of the percentage weight losses in
cold storage shows that the unwrapped control fruit lost 10 times
as much weight as the fruit in pliofilm wrappers. The control
fruit at room temperature averaged a weight loss of more than
six times that of the wrapped fruit.
Of perhaps greater importance than preventing loss in
weight was the action of the pliofilm wrapper in retaining the
original taste and appearance of the fruit during the entire
period of the experiment. As was the case with earlier citrus
varieties, the wrappers preserved the original quality of the
Valencia oranges for a longer time at the lower temperature.
The original green color of the calyx (stem button) was main-
tained by the three types of pliofilm wrapper, while the stem
buttons of the fruit not wrapped became darkened and withered
within a month. Valencia oranges are not as susceptible to
severe pitting as are many other varieties of round oranges, but
pitting does occur, especially at lower temperatures, and is
objectionable from the standpoint of appearance. This pitting
appeared on the unwrapped controls after three weeks, but was
so effectively prevented by the pliofilm wrappers that the symp-
toms appeared on only a few scattered fruit after two months.
The taste of the fruit protected by pliofilm and kept at 370
F. was unchanged during the entire course of the experiment,
while that not wrapped lost the original taste and flavor after
four to six weeks.
Pliofilm in the Preservation of Florida Fruits and Vegetables 23
Fig. 8.-Valencia oranges stored three months at 37 F. (left)
wrapped in 20-gauge pliofilm and (right) unwrapped.
The pliofilm wrappers showed marked efficiency in pre-
venting deterioration of the fruit at room temperature. The
dehydration and change in taste of the unwrapped fruit was
more rapid, rendering it unsalable within two to three weeks,
while the plioseal and 40- and 20-gauge sheet wrappers protected
the fruit from rapid dehydration and change in appearance and
Oranges packed in wire-bound Bruce boxes and standard
nailed boxes showed the same reaction to the wrappers as did
those placed on the shelves for observation. The commercially
packed fruit, however, showed a slightly lower percentage
weight loss, since all the fruit surfaces in the boxes were not
exposed to free circulation of air. The relatively large weight
loss of the unwrapped oranges was soon evidenced by a shrinking
in actual size of the fruit, so that the whole pack became loose
after a short time. The loss in weight of the fruit in the pliofilm
24 Florida Agricultural Experiment Station
Fig. 9.-Valencia oranges stored three months at 37 F. (left)
iosealed and (right) unwrapped.
, rappers at the optimum temperature (370 F.) was less than
2% of the initial weight after a storage period of five months,
and had no discernable effect on the si2e of the fruit.
The plioseal with its glittering transparency proved to be
a most attractive type of wrapper (Fig. 9). The skin-tight, sealed
covering gives a gloss and sheen to the surface of the orange
that adds greatly to its appearance and is a property perculiar to
pliosealing. The plioseal method of covering the fruit with plio-
film has the further advantage of eliminating the material wasted
by allowing a margin for the twist, as is the case when a square
sheet is used to wrap an orange. For example, the 150-size
orange, measuring 3 2/16 inches in diameter, has a surface of
only 30.7 sq. in., but is wrapped with a 12-inch square sheet hav-
ing an area of 144 square inches. Thus the square sheet requires
Pliofilm in the Preservation of Florida Fruits and Vegetables 25
more than four and one-half times as much material as would
be required to actually cover the surface of the fruit with a
plioseal of the same thickness.
Another advantage of the plioseal on oranges is that the pro-
tective covering need not be removed by the storekeeper when
he places the oranges on his counter for display. This allows for
the continued protection of the fruit while on display counter.
A supplementary experiment was conducted to compare the
effect of various types and colors of pliofilm on fruit from Lake
Alfred grown on rough lemon rootstock. Half of these oranges
used in this wrapping experiment were waxed in the packing-
house and the other half left unwaxed, with the object in mind
of comparing the reaction of the waxed and unwaxed fruit
under pliofilm protection.
Forty-gauge pink, red, amber, and clear pliofilm of the NO,
N1 and P4 types were compared at 370 F. Several hundred fruit
were wrapped in each color and type of pliofilm and an equal
number left unwrapped. These were packed in standard boxes
and observations were made and recorded on the shrinkage,
texture, taste, and general appearance. The results showed very
little difference between the wrapped fruits, indicating that the
pink, red, amber, and clear are equally efficient in preservation
of quality in the fruit. Likewise, no marked superiority was
found in any of the types of film tested. All were efficient in
preventing loss in weight and quality but the NO type film was
found to be slightly more efficient in preventing loss in weight.
When the results with waxed fruit were compared to those
with unwaxed fruit, it was found that both sets of fruit reacted
well to pliofilm wrapping. The keeping quality, texture and
taste of the unwaxed fruit was as good as that waxed, indicating
that waxing is not necessary when this protective wrapper is
Tangerines.-The tangerine is probably the most important
orange of the Mandarin group from a commercial standpoint.
It is very popular as a fancy fruit but must be picked, handled
and transported with the greatest of care and must have special
treatment in order that good sound fruit be placed on the market.
All tangerines used in this investigation were of the Dancy
variety grown on sour orange stock. One hundred fifty fruit
were packed per box. Four boxes of tangerines wrapped in 40-
gauge pliofilm were placed at 370 F., 42 F., and room tempera-
26 Florida Agricultural Experiment Station
ture (70-800 F.), as well as an equal number not wrapped. At
intervals of two weeks the effects of the wrapper and tempera-
ture were determined by examination as to decay, pitting, taste,
general appearance and marketability.
Loss in weight of the fruit was determined by placing 75
fruit not wrapped and 75 fruit wrapped in 40-gauge sheet wrap-
pers on shelves at each temperature and weighing individually at
intervals of two weeks.
Table 4 gives the percentage loss in weight of the wrapped
fruit compared with that not wrapped at 370 F., 420 F. and room
temperature (70 F.-80. F.). The percentage loss in weight of
fruit not wrapped was 10 to 20 times as great as that wrapped
in 40-gauge pliofilm. This was true at room temperature, as well
as at cold storage temperatures.
TABLE 4.-PERCENTAGE Loss IN WEIGHT OF PLIOFILM-WRAPPED DANCY TANGERINES
COMPARED WITH THOSE NOT WRAPPED AT 37 F., 420 F. AND ROOM TEMPERATURE
Percentage Loss in Weight After Weeks
Temperature Wrapper 2 4 6 8 10 12
40-gauge sheet 0.58 1.02 1.25 1.75 1.90 2.02
37 F. None (Control) 4.47 7.91 11.47 15.87 18.45 20.57
40-gauge sheet 0.00 0.40 0.82 1.15 1.40 2.00
42 F. None (Control) 4.32 7.83 12.65 16.09 19.04 21.60
70-800 F. 40-gauge sheet 1.08 2.08 4.40 5.98 8.42 10.00
(Room Temp.) None (Control) 11.90 21.59 28.33 34.48 41.72 47.51
Table 5 gives the comparative effect on the keeping quality
and marketability of pliofilm-wrapped and unwrapped Dancy
tangerines. It brings out clearly the beneficial effect of plio-
film wrappers, in that there was always a higher percentage
of marketable fruit in that wrapped in pliofilm than in that
not wrapped. It should be noted also in the table that the low
storage temperature of 370 F. was unfavorable for tangerines
as much physiological breakdown occurred. At the higher tem-
peratures, even though the percent decay was greater, the tan-
gerines kept much better and a higher percentage was market-
able at all times.
Results of the experiment indicate that temperatures below
420 F. are too low for the storage of tangerines. At 420 F. the
fruit can be held for six to eight weeks in good marketable con-
dition if wrapped in pliofilm as compared to two weeks when
TABLE 5.-EFFECT OF PIIOFILI WRAPPERS ON ITI MAILKETABILITA AND KEEPING QUALITY OF DANCY TANGERINES AT 370 F., 42 F., AND
RooM TEMPERATURE (70-80 F.).
After 2 Weeks After 4 Weeks After 6 Weeks After 8 Weeks
% Unmarketable % Unmarketable % Unmarketable % Unmarketable
Temper- Due to % Mar- Due to % Mar- Due to % Mar- Due to % Mar-
ature Wrapper ketable ketable ketable ketable
Ap- fruit Ap- ketable fruit Ap- fruiketable Ap- fruit
Decay pear- Taste Decay pear- Taste fruit Decay pear- Taste frt Decay pear- Taste fruit
ance ance ance ance
40-gauge sheet 0.0 0.0 0.0 100.0 2.0 0.0 0.0 98.0 3.9 10.0* 13.0* 73.1 6.6 15.0* 15.0* 63.4
37 F. None (Control) 0.0 0.0 0.0 100.0 2.3 10.0* 5.0* 82.7 8.0 25.0* 15.0* 52.0 17.3 30.0* 25.0* 27.7
40-gauge sheet 0.0 0.0 0.0 100.0 0.0 0.0 0.0 100.0 3.0 0.0 0.0 97.0 6.0 0.0 0.0 94.0 S
42 F. None (Control) 2.7 0.0 0.0 97.3 4.1 0.0 5.0 90.9 15.1 0.0 10.0 74.9 30.0 10.0 10.0 50.0
Room Temp.40-gauge sheet 3.0 0.0 0.0 97.0 7.5 0.0 0.0 92.5 15.3 0.0 0.0 84.7 20.0 0.0 0.0 80.0
(70-80F.) None (Control) 10.7 5.0 0.0 84.3 44.0 10.0 0.0 46.0 62.7 20.0 10.0 6.3 76.0 24.0 0.0 0.0 "
*Caused by physiological breakdown.
28 Florida Agricultural Experiment Station
not wrapped. At room temperature the wrapped tangerines can
be held two to four weeks in good condition as compared to one
week for those not so protected.
During the past season of 1941 the experiment was repeated,
using 20-gauge (instead of 40-gauge pliofilm) and pliosealing
(stretch-wrapping). Both types of wrapping gave results very
similar to those of the 40- gauge wrapper.
Satsumas.-Two varieties of Satsumas (Owari and Wase)
were used in the experiments conducted over a period of two
seasons (1939-1941). Duplicate experiments were set up for these
varieties and almost identical results were obtained. The results
for one variety, Owari, are presented here. One hundred seventy-
five fruit were packed per box and four boxes each of the
20 wrapped and un-
1 2 3 wrapped fruit
were placed at
SATSUMA ORANGES temperatures o f
370 F., 42 F., and
700 F. At inter-
15 vals of two weeks
the effects of the
tures were deter-
mined by thor-
1 as to loss in
Spitting, taste and
ance. In addition
75 fruit not wrap-
ped and an equal
5 number wrap-
Sped in 40-gauge
0 2 4 8 10 12 14 placed on shelves
Time in Storage weekss and individually
Fig. 10.-Percentage weight loss of satsuma or- weighed every
anges held at three temperatures wrapped in 40-
gauge pliofilm and unwrapped. At room temper- two weeks.
ature (70-80 F.) 1, unwrapped and 4, wrapped; Table 6 gives
at 42 F. 2, unwrapped and 5, wrapped; at 37o F. 3, perc loss
unwrapped and 6, wrapped percentage loss
Pliofilm in the Preservation of Florida Fruits and Vegetables 29
in weight of the wrapped fruit compared to that not wrapped
at 370 F., 420 F., and 70 F. for the 1939 season. The percentage
loss in weight is given for the fruit packed in crates as well as
for those on shelves which were individually weighed. Fruit
not wrapped lost from five to 10 times as much weight as that
wrapped (Fig. 10). It may be noted from the table that the loss
in weight of fruit packed in crates is always less than that set
out for display or on shelves. In the case of the unwrapped fruit,
approximately one-half as much weight was lost from the fruit
in crates as from that on display shelves. For the wrapped fruit
this difference was much smaller. Similar results were obtained
for the 1940 season, as shown in Fig 10.
The lowest temperature at which Satsumas kept most sat-
isfactorily was found to be 37' F. At this temperature the
wrapped fruit remained marketable for three months. Decay was
negligible and no physiological breakdown occurred as with
tangerines at this temperature. Results at 42 F. duplicated
Lh )se for the fruit at 37 F. in all respects except that the decay
and percentage weight loss were slightly higher. At 700 F., the
temperature of the retail stand, the time that the fruit remained
in a marketable
more than dou-
bled by the use
"of pliofilm (Fig.
grown on sour
were used in the
both 1939 and
1940. During the
1939 season the
fruit was wrap-
Si ped when fully
mature in 40-
g gau ge pliofilm
and packed in
Fig. 11.-Satsuma oranges after two weeks at standard boxes.
room temperature (70-800 F.). Top, unwrapped;
bottom, wrapped in 40-gauge pliofilm. Five boxes of
TABLE 6.-COMPARISON OF Loss IN WEIGHT oF OWARI SATSUMA ORANGES IN 40-GAUGE PLIOFILM WRAPPERS WITH THOSE NOT WRAPPED
AT 370 F., 42' F. AND 70 F.
Percentage Loss in Weight After Weeks
2 4 6 8 10 12
> a > a a aE a aE a
40-gauge sheet 0.27 0.23 0.53 0.31 0.70 0.68 1.02 0.98 1.22 1.04 1.40 1.26
(Cold Storage) None (Control) 4.04 2.13 5.20 3.29 6.98 3.55 9.24 4.38 10.95 4.90 12.42 5.82
40-gauge sheet 0.47 0.31 0.75 0.36 0.85 0.50 1.27 0.80 1.52 1.24 1.88 1.40
(Cold Storage) None (Control) 4.00 1.82 5.19 3.21 6.99 3.58 9.42 4.17 11.20 4.87 12.92 6.10
40-gauge sheet 1.03 0.82 2.06 1.00 4.21 2.23 5.23 2.51 7.10 3.02 8.93 4.12
70' F. t
(Retail Stand) None (Control) 10.78 3.16 15.41 5.47 22.33 10.17 31.48 15.70 38.62 18.98 42.10 20.16
TABLE 7.-EFFECT OF PLIOFILM WRAPPERS ON THE SHRIVELING, QUALITY, TASTE, RIND PITTING AND DECAY OF TEMPLE ORANGES AT 37 F.,
AND 700 F., AFTER INTERVALS OF THREE AND SiX WEEKS.
Time Temperature Wrapper Shriveling Quality Taste Rind Pitting Decay 1
(Cold 40-gauge sheet None Excellent Excellent None None
Storage) None (Control) Slight Good Good Slight Slight
3 weeks 70* F.
(Retail 40-gauge sheet None Good Very good None Medium
Stand) None (Control) Severe Poor Fair Slight Very heavy
(Cold 40-gauge sheet None Very good Very good None Slight
After Storage) None (Control) Severe Fair Fair Heavy Medium
(Retail 40-gauge sheet Slight Fair Fair None Medium
Stand) None (Control) Very severe Poor Poor Heavy Very heavy .
32 Florida Agricultural Experiment Station
wrapped and two boxes of unwrapped fruit were placed at each
temperature, 37" F. and 70 F. At regular intervals inspection
was made and the wrapped fruit compared with that not wrapped.
Table 7 gives the effect of pliofilm wrappers on shrinkage, qual-
ity, taste, rind pitting and decay of Temple oranges at 370 F.
and 700 F., after intervals of three and six weeks. This tabula-
tion shows the pliofilm to be very efficient in the prevention of
shriveling, rind pitting, and decay, and in the preservation of
quality and taste. After six weeks no shriveling could be
detected in the wrapped fruit at 370 F. and only slight
shriveling at 700 F., compared with very heavy drying and
shriveling of the unwrapped fruit at both temperatures.. Rind
pitting was controlled entirely by the pliofilm wrappers at both
temperatures, while it was severe after six weeks in the fruit
not wrapped, especially at 370 F. Decay was not controlled en-
tirely by the wrappers but at both cold storage and retail stand
temperatures the percentage decay was less in the wrapped fruit
than in that not wrapped.
Taste and quality were preserved for a period of three
months in the wrapped fruit held at 370 F., and for four and five
weeks in that at 70' F.
The work was repeated during the 1940 season with all con-
ditions being the same except that 20-gauge pliofilm and plioseal
were used instead of 40-gauge pliofilm. The results showed 20-
gauge and plioseal to be equal to 40-gauge pliofilm in most re-
spects except in the case of percentage loss in weight. The loss in
weight was less in the fruit wrapped in 40-gauge than either the
20-gauge or plioseal but this additional protection did not justify
the higher cost of the wrapper.
The attractiveness of the plioseal was outstanding in that the
transparent wrapper in addition to accentuating the good color
and quality of the Temple orange, also gave the fruit a high gloss
which improved its appearance immensely. The amount of ma-
terial used is approximately one-fifth as much for the plioseal as
for the sheet wrapper, thus effecting an economy in material
when this type wrapper is used.
Duncan.-Forty boxes of the Duncan variety were used
during the 1940-41 season in the wrapping investigations on
grapefruit. Half of the fruit was washed in a commercial
packinghouse and the other half was untreated. The experi-
Pliofilm in the Preservation of Florida Fruits and Vegetables 33
ment was designed to test the effect of 40-gauge pliofilm sheet
wrappers on grapefruit at 42 F. and 700 F. The fruit was packed
in field boxes in such a manner that each box contained the
20 same number of
DUNAN RAPEFRUIT and small fruit.
Table 8 gives
loss in weight of
15 the fruit wrap-
ped in 40-gauge
pliofilm and that
V/ unwrapped, at
1 2 the two tempera-
o tures. High
U weight loss at
both 70 and 42
F. of the unpro-
tected fruit was
s o o n evidenced
5 by an accompan-
ying loss of firm-
S ness and appear-
ance. (Fig. 12).
S--- Within three
weeks, the fruit
0 2 4- 6 8 10 12 4- at 70 F. was
Time in Storage (weeks)
Fig. 12.-Percentage loss in weight of Duncan
grapefruit during 14 weeks' storage, wrapped in salable due to
40-gauge pliofilm and unwrapped. At storage drying, whi e
temperature of 70 F. 1 represents unwrapped and
3 wrapped fruit; at 42 F. 2, unwrapped and 4, that in the wrap-
wrapped. per had lost less
than 1 percent of its total weight. The data show that, for
both these temperatures, pliofilm wrappers reduced the loss of
weight to less than 1/10 of that of the unwrapped control sam-
ples. Of equal importance was the control of rind pitting by the
wrappers. General pitting appeared in the unwrapped fruit af-
ter three to four weeks and became severe after five weeks at
42 F., but on the wrapped samples, showed only slightly after
six weeks. Pitting was more severe at 42 F. than at 700 F.,
but the loss in weight was more gradual at the lower tempera-
TABLE 8.-PERCENTAGE Loss IN WEIGHT or DUNCAN GRAPEFRUIT AS AFFECTED BY PLIOFILM WRAPPERS AT 420 F. AND 700. F.
Percentage Loss in Weight After Weeks
Temperature Wrapper 1 3 5 7 9 11 13 15
42 40-gauge sheet 0.16 0.28 0.61 0.78 0.84 1.28 1.41 1.65
(Cold Storage) None (Control) 1.98 3.92 6.57 9.45 12.69 15.30 16.13 17.88
700 F. 40-gauge sheet 0.44 0.72 1.25 1.60 1.90 2.50 2.80 3.51
(Retail Store) None (Control) 3.96 7.86 11.95* 15.90 18.70 25.80 30.00 37.20 .
TABLE 9.-PERCENTAGE Loss IN WEIGHT OF PERSIAN LIMES AS AFFECTED BY VARIOUS TYPES OF PLIOFILM PROTECTION AT 370 F., 420 F.,
AND 700 F.
Percentage Loss in Weight After Weeks
Temperature Wrapper 1 2 3 5 6 7 8
(3701d t (Same as 42 F.) Temperature too low. All fruit broke down physiologically.
(Cold Storage) (o
20-Gauge sheet Plioseal 0.38 0.54 0.74 0.92 1.27 1.46 1.79
420 F. (Stretch-wrap) 0.19 0.40 0.57 0.77 0.95 1.10 1.29
(Cold Storage) 20-Gauge liner 0.22 0.40 0.54 0.78 0.86 0.98 1.10
None (Control) 3.70 6.18 9.29 13.45 15.71 17.24 18.91
20-Gauge sheet 0.54 1.89 2.62 3.88 4.98
70 F. Plioseal (Stretch-wrap) 0.62 0.72 0.82 1.29 1.64
(Retail Stand) 20-Gauge liner 0.53 1.15 1.69 2.30 2.71
None (Control) 6.63 12.87 16.34 20.14 23.54
*Unsalable from this time on.
I', .:j.',, in the Preservation of Florida Fruits and Vegetables 35
The effect of the pliofilm wrapper on the percentage of fruit
lost by decay, other than the prevention of "nesting", was not
appreciable while the unwrapped fruit, weakened through exces-
sive drying and pitting, decayed rapidly.
The original color, texture, acidity, flavor and juice content
of the wrapped fruit was retained to a remarkable degree by the
pliofilm wrapper through the entire course of the experiment.
Some of this fruit left under the same conditions for three months
had changed only slightly in appearance (Fig. 13) and was in-
distinguishable from fresh fruit in taste, flavor and texture.
Throughout the entire seven months of observation it was
noted that no sprouting of seeds occurred in the wrapped fruit
at any of the temperatures but that in unwrapped fruit sprouting
occurred after three weeks' storage at 70' F. and after six weeks
at 42 F.
There was very little difference in results obtained with the
washed and unwashed fruit, results with unwashed fruit being
slightly better. Since this difference was so slight, only the data
for the unwashed fruit are given here.
Fig. 13.-Appearance of Duncan grapefruit after three months'
storage at 42 F. (left) wrapped in 40-gauge pliofilm and (right) un-
36 Florida Agricultural Experiment Station
Marsh Seedless, Silver Cluster and Singletary Varieties.-
During two seasons (1939-1941) similar experiments were carried
out with Singletary, Silver Cluster and Marsh Seedless varieties.
In these experiments fruit of each variety were wrapped in 40-
gauge pliofilm and 100 placed on shelves with an equal number
unwrapped at each of two cold storage temperatures-37 F. and
420 F.-and at 700 F. Three boxes each of wrapped and unwrap-
ped fruit were packed in regular packing boxes and loss in
weight, quality, texture, taste and percent decay determined over
a period of three months. All varieties reacted favorably to the
pliofilm protection. Marsh Seedless did not react as well un-
der storage conditions as the two seedy varieties but, in all cases,
the differences were so slight when compared with results ob-
tained with the Duncan variety, which are presented above, that
the data are not given here. Investigations on these varieties do
show, however, that the advantages derived from wrapping
grapefruit in pliofilm are not confined to one variety and were
consistent over a period of three seasons.
Persian Limes.-Mature green Persian limes were placed in
three types of protective wrappers; 20-gauge pliofilm sheet wrap,
plioseal, and liners of 20-gauge in small commercial packing
cartons, and were compared with the unwrapped control at each
of three temperatures, 370 F., 42' F., and 700 F. Two hundred
were placed in each type wrapper at each temperature and an
equal number left unwrapped for comparison.
The lowest temperature, 370 F., proved to be impractical,
since physiological breakdown occurred in all samples within a
month. For storage purposes, 420 F. was found to be the best
temperature. The fruit held the initial green color at this tem-
perature for two months, and the severe pitting and dehydration
occurring in fruit not wrapped was controlled remarkably well by
the two types of wrappers and by pliofilm liners.
At 70 F. dehydration and change in color were limiting fac-
tors. Loss of moisture was effectively controlled by wrappers
and the carton liner, but color change was only slightly retarded.
Limes are marketed while having a full green color, since light
areas or streaks place them in the classification of second grade
or cull fruit. This color change will occur after approximately
two weeks at ordinary temperatures, but this time is sufficient
for ordinary marketing processes without color change.
Pliofilm in the Preservation of Florida Fruits and Vegetables 37
Table 9 shows the percentage loss in weight of the limes at
42 F. and 700 F. Severe pitting of the rind was general
throughout the unwrapped fruit at 420 F. within eight days,
causing them to be unmarketable. Slight pitting occurred in the
fruit held in wrappers and lined cartons after six weeks.
The severe weight loss of limes in the usual marketing chan-
nels where refrigeration is not commonly used could best be con-
trolled by using inexpensive 20-gauge liners in the cartons now
used for packaging. Table 9 shows the loss in weight of the un-
wrapped fruit at fruit stand temperature (70 F.) to be three to
10 times as high as for the fruit in wrappers or pliofilm-lined
It is evident that Persian limes will not tolerate a low stor-
age temperature, since the fruit held at 370 F. developed physio-
logical breakdown within a relatively short period. The sheet
wrapper, plioseal, and carton liners were effective in preventing
severe drying and the consequent loss of juice.
Key Limes.-Key limes reacted very favorably to wrapping
ii 20-gauge pliofilm, either individually or in groups of six and
12 per wrapper. The freshness, quality and taste were pre-
served by the pliofilm wrapper as well as by the carton liner
irade of 20- and 40-gauge pliofilm. At all temperatures except
17 F. wrapped Key limes or those protected with liners re-
mained marketable four times as long as those not so protected.
Both wrapped and unwrapped Key limes broke down physiolog-
ically after two weeks' storage at 37' F. The best storage tem-
perature for Key limes was found to be 42' F.
Nagami Kumquats.-Nagami kumquats were placed in quart
and two-quart baskets which were lined with 40-gauge pliofilm.
The fruit was first packed in a frame which was lined with
pliofilm and which fitted the basket when inverted. This per-
mitted the fold to be on the bottom of the pack when placed in
the basket and gave a smooth transparent covering for the top
of the basket.
The fruit was picked and packed with and without leaves.
Several baskets were placed at 370 F., 42 F., and room tempera-
ture (700 F. 800 F.), together with an equal number of baskets
not protected by the liners as controls on the conditions of the ex-
periment. Very good results were obtained at all temperatures.
The pliofilm liner was outstanding in holding the kumquats in a
38 Florida Agricultural Experiment Station
state of harvest freshness and good quality three to five times
longer than that not so protected at both cold storage and retail
The original color and freshness of the leaves as well as those
of the fruit were preserved by the pliofilm liner. Shriveling was
not detected in the wrapped fruit at any time during the six
weeks' holding period even at the higher temperatures.
(Peeled, stretch-wrapped, ready to eat)
A large proportion of the consumer public likes to eat peeled
oranges, as well as to drink the juice. Florida oranges generally
have a much thinner peel and contain a higher percentage of
juice than citrus grown in other areas. These characteristics
make them difficult to peel by hand and inconvenient to eat in
this manner because of their juiciness. Peeled oranges, offered
for sale in a sanitary, convenient, sealed package that would
preserve the initial taste, texture, and flavor of the fruit should
prove popular because of their appeal to the consumer.
Experiments were initiated with Valencia oranges in an
attempt to apply the benefits of moisture-proofness and trans-
parency of pliofilm to a new method of offering Florida oranges
to the public.
The washed Valencia oranges were precooled to 340 F. and
the flavedo (outer peel) was removed with a knife, taking care
that all the oil cells were removed. This left the orange covered
by the white albedo (inner peel). These oranges were packaged
in three ways: Wrapped in a 20-gauge sheet with a twist closure,
pliopeeled, and the orange cut in two and the halves individually
Large quantities of oranges were prepared and packaged in
each of the above manners of pliofilm wrapping and held at 34'
F. and 370 F. Taste tests were made on these samples at two-
day intervals to determine how long the samples could be stored
without change in flavor and texture. The percentage weight
loss of the pliopeel Valencia oranges in cold storage at 340 F. or
at 370 F. was only slightly greater than that of unpeeled Valencia
oranges (Table 3), and this small weight loss had no apparent
effect on the juiciness, even after a period of six weeks.
The type of wrap did not have an appreciable influence on
the keeping quality of the prepared oranges. Samples were
kept on shelves without distinguishable changes in flavor for a
Pliofilm in the Preservation of Florida Fruits and Vegetables 39
Fig. 14.-Pliopeel oranges: left, halves and right, whole fruit.
minimum of 21 days. Some samples retained their original
quality for a period of six weeks. In no case did mold growth
appear in less than one month after wrapping.
The types of packaging applied to the oranges differed some-
what in their attractiveness. The pliopeel oranges with the
glistening transparent wrapper proved to be more desirable than
the sheet wrapper. The halved pliopeel oranges proved to be
the most attractive and convenient of all the types prepared.
Figure 14 shows the sales appeal of the juicy oranges, whole and
in half-sections, attractively displayed in a sanitary transparent
-~-'ed covering. The small amount of juice liberated from the
j juice sacs and retained under the flat pliofilm cover on the
pliopeel half-section did not differ in taste from the other sec-
tions of the orange. This was true for the entire time of storage.
Market trials of pliopeel Valencia oranges were conducted at
DeLand, Florida, in cooperation with a representative of the
Florida Citrus Exchange. Fruit having a high juice content
were selected and the flavedo was peeled off under sanitary con-
40 Florida Agricultural Experiment Station
editions. One to two weeks' supply was prepared in advance and
that not to be used immediately was returned to storage.
The sales display was made from a five cubic foot refrigera-
tor with a glass door. The pliopeel fruit was stacked on the
metal shelves in such way that the purchaser was able to select
any fruit. A sharp knife and wooden cutting board were located
on the top shelf. The display refrigerator was located opposite
the soft drink dispensing unit in a service station. Five cents
was charged for each orange and, when the sale was made, the
customer was instructed to slice the orange in half on the cutting
board. The pliofilm continues to cling snugly to the surfaces of
the peeled orange after it has been cut, protecting the hands from
any juice that may escape from the orange while it is being
eaten. The substitution of the pliofilm for the outer peel pre-
vents the objectionable rind oil taste when the fruit is eaten in
this manner. This new method of preparing and selling oranges
was very popular and found a ready acceptance by the public.
The experiment was continued for several weeks and its con-
tinued success indicated that the novelty of the product was not
responsible for its customer-appeal. Nearly as many sales were
made of oranges from the refrigerated showcase during the course
of the experiment as there were of soft drinks from the adjacent
The object of offering such ready-to-eat oranges to the pub-
lic would be to encourage their consumption at baseball parks,
service stations and confectioners' stores. In this way it should
supplement the ordinary sale of fruit. The sale of these oranges
at public gatherings such as baseball games could be made most
conveniently from iced trays by vendors, while the refrigerated
unit would be more suitable for permanent sales displays.
Removal of the outer peel with its oil sacs permits the use
of skin-blemished fruit for the ready-to-eat oranges. A large
amount of the high juice quality fruit brings a relatively low price
because of peel imperfections. This fruit could well be used,
since the removal of the outer peel would make this type of fruit
indistinguishable from the best grade oranges. Preparation of
pliopeel fruit should be carried out under sanitary conditions,
using only the best juice-quality fruit.
The marketing of such fruit is simplified to an extent by the
good keeping qualities at low temperatures, a minimum of three
weeks at 34' F. to 370 F. Either fresh or storage fruit may be
used, insuring an all-year supply.
Pliofilm in the Preservation of Florida Fruits and Vegetables 41
Prepared oranges may be preserved indefinitely without
change in taste by quick-freezing and storing at a temperature
below freezing. The pliofilm covering prevents dehydration and
change of taste. The fruit may be thawed just before eating.
Experiments were instituted in cooperation with several
grocers and shippers from various sections of the citrus belt in an
effort to apply the results of the pliofilm investigations to com-
mercial methods of wrapping and packing. The object was to
subject the pliofilm wrap to a test in the regular market channels
and to measure its ability to preserve the original quality of the
fruit under commercial storage conditions.
Twenty-gauge pliofilm sheets were used in the experiments.
The individual sheets were separated with tissue for greater ease
in handling. Ten-inch and 12-inch square sheets were used,
and sizes 126's to 325's were packed. A total of 2,000 standard
and Bruce boxes of pliofilm-wrapped Valencias were packed in
six packinghouses during the first two weeks of June 1941. Five
hundred boxes wrapped with the tissues commonly in use were
employed as controls for comparison. When Bruce boxes were
used the control fruit was left unwrapped.
The actual wrapping and packing operations were carried out
as nearly like the routine operations as possible so that the pro-
duction process would not be affected. Firm first-grade fruit was
used and an effort was made to protect it from bruising.
Comparatively little difficulty was encountered in substitut-
ing the pliofilm for the regular paper wrappers. The novelty of
this new wrap slowed the speed of the packers considerably until
they had packed several boxes. Oranges in pliofilm wrappers
made a very attractive pack, much improved in appearance over
the ordinary paper tissue. They also slipped into place more
easily with less bruising or crushing when the pack was sub-
jected to pressure on the heading machine. This operation press-
es the top firmly on the standard box before it is fastened with
nails and metal strips. The fruit was precooled and shipped in
iced refrigerator cars to Northern market areas, where it was
placed in storage at temperatures ranging from 340 F. to 37' F.
and 80 percent relative humidity.
Before shipment and from each of the six lots of fruit packed,
six to 10 half-boxes of the pliofilm-wrapped and tissue-wrapped
fruit were taken by truck to the refrigeration plant at the Experi-
42 Florida Agricultural Experiment Station
ment Station in Gainesville, Florida, and placed in storage at
conditions as nearly approximating those of commercial storage
as possible. Regular inspection of the fruit was made and rec-
ords were taken of the loss of size and weight as well as changes
in texture, appearance and taste. These are tabulated in Table
Regular inspections of the fruit in the commercial storage
houses were made by representatives of the shippers. Reports
of these inspections were found to compare well with results ob-
tained with corresponding lots of fruit stored in the refrigeration
plant at the Experiment Station.
The shippers placed the Valencias on the fruit auctions in
the various cities where they judged that the best price could be
obtained. As is shown in Table 10, the pliofilm preserved the
original quality of the oranges during the three months' storage
period, affording the shippers an opportunity to choose the
optimum time of marketing.
Pitting, shriveled and blackened stem buttons, shrinkage,
softness, and loss of turgidity and flavor were present in the
unwrapped and paper-wrapped oranges shipped and stored un-
Fig. 15.-Valencia oranges stored three months at 370 F. wrapped in
20-gauge pliofilm (left) and tissue (right).
Pliofilm in the Preservation of Florida Fruits and Vegetables 43
der the same conditions. These symptoms, either directly caused
or greatly influenced by dehydration (loss of moisture), were
practically eliminated by the use of the experimental wrapper,
proving that pliofilm is practical under commercial methods of
shipping, storage and marketing (Fig. 15).
As each lot of fruit was sold on Northern markets, half boxes
of pliofilm-wrapped and paper-wrapped fruit were removed to
room temperature to duplicate the conditions of retail stand tem-
peratures. It was found that the paper wrappers became wet
from condensation of moisture, causing a soggy condition of the
pack. When wet these wrappers possessed only a small fraction
of their original tensile strength, while the condensation of mois-
ture on the pliofilm did not affect its strength and the pack was
dry again after a few hours of natural evaporation. The per-
centage weight loss of the fruit was much more rapid after re-
moval from storage to room temperature, averaging slightly
more than 1 percent per day for oranges in paper wraps. This
weight loss was 10 times more than for oranges protected by
pliofilm, which was slightly under one-tenth of 1 percent per day.
The percentage of rots after removal from storage was higher
than it would have been for fresh fruit at room temperatures,
but the percentage of fruit lost by decay was always less in that
wrapped in pliofilm.
The final measure of the success of any commercial experi-
ment may be judged by a comparison of prices. The pliofilm-
wrapped oranges were sold at auctions in Chicago, Philadelphia,
and New York after being in storage for a period varying from
five weeks to three months. For purposes of comparison the
average auction prices of the brands from each of the houses
was taken five days after packing each lot of fruit. These were
averaged to give the price, had the shipments been sold imme-
diately as they reached the market area. The other prices are
averages of direct statements of the sale of the fruit in pliofilm
and tissue wrappers.
Average market price at time of packing .--------------$2.35 per box
Average market price after storage in paper wrappers.-..-. 2.64 per box
Average market price after storage in 20-gauge pliofilm
wrapper ---------- --------- -------- ---- 3.62 per box
The pliofilm-wrapped fruit found ready acceptance on auc-
tion markets and sold well in retail stores, though competing
with fruit from other areas.
It was found that Valencia oranges picked and stored in this
TABLE 10.-COMPARISON OF THE CONDITION OF VALENCIA ORANGES WRAPPED AT VARIOUS PACKINGHOUSES IN 20-GAUGE PLIOFILM TISSUE
AND NOT WRAPPED, AFTER DIFFERENT STORAGE INTERVALS.*
(Average of from six to 10 half-boxes)
** Percent Unmarketable Due to Percent Percent
Lot Mech. Rind Slight Button General Condition
No. Wrapper Shrinkage Injury Decay Pitting Pitting Discoloration
After 2 weeks
1 Pliofilm None ..-- --- Very good. No change.
1 Tissue Slight -- -- -Good. Slight drying.
2 Pliofilm None -- -- Very good. Firm.
2 Tissue None -- -- Good. Slight softening.
3 Pliofilm None -- -- --Very good. Firm.
3 None Slight -- -- Very good.
4 Pliofilm None --- --- --- --- Very good. Firm.
4 Tissue Slight ---- ----- Good. Slight softening.
5 Pliofilm None ---- -- --- Very good. Firm.
5 Tissue Slight ----- --- -- Good. Slight softening.
6 Pliofilm None -- Very good. Firm.
6 None Slight -- --- Good. Slight softening.
After 4 weeks
1 Pliofilm None 0 0 0 2 1 Firm
1 Tissue Medium 0 0 0 28 10 Soft stem, and shriveled.
2 Pliofilm None 0 0 0 2 2 Firm, good texture.
2 Tissue Slight 1 0 0 8 6 Soft about stem.
3 Pliofilm None 1 0 0 3 5 Firm. Good texture.
3 None Medium 0 0 0 20 20 Slightly soft.
4 Pliofilm None 0 0 0 3 4 Firm.
4 Tissue Slight 0 0 0 12 7 Slightly soft.
5 Pliofilm None 1 0 0 0 2 Firm.
5 Tissue Slight 0 0 0 10 20 Soft (stem end drying).
6 Pliofilm None 0 0 0 1 Firm.
6 Tissue Medium 1 0 2 5 Slightly soft.
After 6 weeks
1 Pliofilm None 0 1 0 9 6 Generally firm.
1 Tissue Severe 2 0 2 50 20 Very soft. Wrinkling about stem-end. ^
2 Pliofilm None 0 1 0 5 7 Firm. Good texture and appearance.
2 Tissue Medium 1 0 0 20 18 Soft about stem-end.
3 Pliofilm None 1 1 0 6 10 Firm and good.
3 None Severe 0 1 2 50 40 Drying out about stem-end.
4 Pliofilm None 1 1 0 5 10 Firm, good texture and appearance.
4 Tissue Medium 1 1 0 20 30 Soft, stem-end drying.
5 Pliofilm None 1.7 0.3 0 0 7 Generally firm and good.
5 Tissue Medium 0 0 0 35 45 Dry out about stem-end.
6 Pliofilm Slight 1 0 0 0 8 Firm.
6 Tissue Severe 0 1 1 30 30 Stem-end drying.
After 12 weeks
1 Pliofilm None 3 1 1 5 10 Firm, good texture.
1 Tissue Very severe 4 2 75 20 80 Badly burnt stems, shriveled, softened
2 Pliofilm None 1 1 0 2 12 Firm, with excellent texture, taste fair.
2 Tissue Severe 1.5 1 15 12 40 Softened, misshapen, with storage taste.
3 Pliofilm None 1 2 0 5 15 Green calyx firm, good color, texture
Tissue and flavor.
3 None Severe 1 3 50 50 70 Soft, Shriveled, badly pitted with burnt
stems and storage flavor.
4 Pliofilm None 2 2 0 0 18 Fruit firm and hard, too high bulge in
Tissue box. Good taste.
4 Severe 2 2 10 15 55 Storage taste, tender burnt stems.
5 Pliofilm None 1 1.75 0 0 12 Firm, green stems good appearance
Tissue and flavor.
5 Severe 1 2 10 25 75 Stem-end drying, soft, badly burnt
6 Pliofilm None 1 2 0 1 10 Very firm good taste. Appearance
Tissue unchanged. Q
6 Severe 1 2 20 25 45 Soft, misshapen, with storage taste.
*Stored in Experiment Station refrigeration plant under conditions approximating those of commercial storage
"**Lot No. 1 held at 34' F., all others 37' F. C
46 Florida Agricultural Experiment Station
manner at full maturity were superior in appearance and taste to
those which had been left on the tree for very late-season ship-
Protection of Florida's juice-heavy citrus fruit during ship-
ment and marketing presents many advantages to the industry.
Pliofilm wrappers protect the fruit from mechanical abrasion
during shipment and prevent "nesting", the spread of mold
spores from infected fruit to those surrounding it. Protection
from shrinkage and other effects of dehydration afforded by this
transparent moisture-proof wrapper prevents the decrease in
size of fruit and would necessitate far less bulge in the fruit
pack than is now the common practice. If a pack with less bulge
were used, far less fruit would be crushed and bruised during
packing and transit. Bruising and dehydration are the principal
causes of quality loss in fresh fruit shipments.
The performance of citrus in pliofilm wrappers at room
temperatures indicates that this continued protection is very
valuable, since most of the Florida fruit shipped to Northern
market areas remains in retail stores and homes for an appre-
ciable time before consumption. Prevailing low humidities un-
der these conditions cause severe dehydration.
Fancy fruit such as Mandarin oranges may be held in plio-
film for a sufficiently long period to extend the shipping season
and in this way be of aid in avoiding an over supply on the mar-
ket. Although these varieties are considered comparatively per-
ishable, their reaction to the pliofilm wrapper indicated that
this fruit could be held at optimum conditions much longer than
when not wrapped.
The use of the pliofilm wrapper on stored fruit permitted
the marketing season to be extended into the summer months.
A greater volume of oranges and grapefruit packed in this man-
ner and stored both for Northern markets and for local consump-
tion during the summer season would tend to relieve the market
from a condition of oversupply during the peak of the harvest
The pliopeel oranges should provide an outlet for Florida
oranges through sources which are not at present interested in
The plioseal proved to be the most efficient method of pro-
tection based on retention of quality, appearance, and flavor, as
well as economy of material. The 40-guage sheet wrapper was
Pliofilm in the Preservation of Florida Fruits and Vegetables 47
the most efficient in preventing dehydration, but this added pro-
tection was not sufficient to compensate for the added cost over
either the 20-gauge sheet wrapper or the plioseal.
The plioseal wrapper proved to be the most attractive type
used. The mechanical principles involved in the pliosealing
operation are such that they could be incorporated into an auto-
matic wrapping machine that would provide the speed and econ-
omy necessary for production lines in packinghouses. Commer-
cial interests are now working on the development of such a
Although printing is possible on pliofilm, this operation is
not necessary since the transparency of this material allows the
brand stamped on the fruit to be clearly seen through the wrap-
per. This transparency also permits the merchant to display the
qualities of the fruit without removing the wrapper.
OTHER FLORIDA FRUITS
The highly seasonal character and marked perishability of
numerous other Florida fruits are major factors limiting the
economic importance of these crops. Improved methods of pack-
aging, handling and distributing would allow fancy fruits such as
persimmons, avocadoes, mangos and peaches to be placed in more
distant market areas in a state of harvest freshness and would
also permit the fruit to be held in storage past the regular sea-
Tanenashi and Fuyugaki varieties of persimmons were pick-
ed when showing full color but still firm. This is the stage of
maturity at which the fruit is picked for shipping. The effect
of wrapping with 40-gauge pliofilm was evaluated by comparing
wrapped fruits with those not wrapped at two cold storage tem-
peratures (37 F. and 420 F.), and at retail stand temperature
(70 F.). The fruit was packed in lugs and individual samples
were weighed at various intervals and these weights were ave-
raged to determine percentage loss in weight, as presented in
Table 11. Five lugs, each containing 24 fruit wrapped in plio-
film and an equal number of unwrapped samples, were placed
at each of the three temDeratures.
Cold storage temperatures and the pliofilm wrapper had the
effect of retarding softening of the fruit. Persimmons should
be eaten when soft-ripe, at which time their astringency has dis-
appeared. Both varieties of fruit not wrapped in pliofilm soft-
TABLE 11.-EFFECT OF PLIOFILM WRAPPERS ON THE LOSS In WEIGHT AND RIPENING OF TANENASHI AND FUYUGAKI PERSIMMONS AT 3'7
F.. 420 F., AND 700 F.
Percentage of Loss in Weight Soft Ripe
Variety Temperature Wrapper After Weeks After Days
1 2 3 4/
40-guage sheet 0.00 0.19 0.38 0.76 31
370 F. No Wrap 0.57 2.67 3.82 5.85 24
Tanenashi 42' F. 40-guage sheet 0.00 0.21 0.21 0.42 30
No Wrap 0.62 1.46 2.30 5.14 23
700 F. 40-guage sheet 0.17 0.34 14
No Wrap 4.80 6.73 9
370 F. 40-guage sheet 0.00 0.40 0.40 0.60 28
No Wrap 1.70 3.45 4.74 7.76 21
Fuyugaki 42o F. 40-guage sheet 0.00 0.00 0.40 0.60 28
No Wrap 2.14 3.86 5.15 7.72 20
70* F. 40-guage sheet 0.48 0.48 0.78 14
No Wrap 6.09 7.90 9
Pliofilm in the Preservation of Florida Fruits and Vegetables 49
ened and lost their astringency after a month's storage at the
lower temperatures, while the same effect was observed in the
fruit at 70 F. in nine days. The pliofilm wrapper retarded the
ripening process five to eight days and was effective in prevent-
ing the shriveling and storage spotting observed in the unwrap-
ped fruit. The average weight loss of all unwrapped fruit at
the three temperatures at the end of the storage period was
found to be six-tenths of 1 per cent of the total weight, while
that not protected showed a loss of 7 percent, approximately 12
times as much. As is shown in Table 11, the weight loss of
both the wrapped and unwrapped fruit varied directly with tem-
perature; that is, the larger weight losses occurred at the higher
The optimum temperature for the storage of persimmons
was found to be 420 F. At this temperature the time required
for the fruit to become soft-ripe was the same as that at 370 F.
but the storage spotting appearing on the unwrapped control
fruit at the latter temperature was less severe.
Taste and appearance of the pliofilm-wrapped fruit were su-
perior to the unwrapped, and the retention of moisture in the
wrapped fruit was evidenced by excellent texture.
At all three temperatures the softening of the persimmons
was retarded by the pliofilm. The wrapped fruits softened ap-
proximately one week later than those not wrapped. Also, the
wrapped fruit at the cold storage temperatures of 42' F. and
370 F., after reaching the edible soft-ripe stage, remained mar-
ketable three weeks longer than that not wrapped, and at the
retail stand temperature of 700 F. one week longer in the edible
Haden mangos were picked when mature, showing full color
but still firm. Wrapping fruit with 20-gauge pliofilm and plio-
seal was evaluated by comparing wrapped and unwrapped fruit
at two cold storage temperatures, 370 F. and 420 F., and at the
temperature of the retail stand (700 F.). Six lugs containing
12 fruit each were used for each wrapper and control at each
of the three temperatures. The experiment was conducted over
a period of two seasons (1940-1941). Only the results for 1940
are given here.
Both cold storage and pliofilm wrappers retarded softening
of the fruit. The time required for softening was twice as long
for fruit wrapped in 20-gauge pliofilm and plioseal as that not
TABLE 12.-EFFECT OF PLIOFILM WRAPPERS ON THE KEEPING QUALITY OF HADEN MANGOS AFTER Two AND FOUR WEEKS AT 37 F.,
420 AND 70 F.
Time Temperature Wrapper Shriveling Quality Taste Spotting Decay
37' F. 20-gauge sheet None Excellent Excellent None None
Plioseal None Excellent Excellent None None
None (Control) Medium Fair Fair Slight Slight
Two 42 F. 20-gauge sheet None Very Good Very good None None .
Plioseal None Very Good Very good None None
Weeks None (Control) Medium Fair Fair Slight None
700 F. 20-gauge sheet None Good Good None None
Plioseal None Good Good None None
None (Control) Heavy Poor Poor Heavy Medium
37" F. 20-gauge sheet None Very good Very good None None
Plioseal None Very good Very good None None
None (Control) Heavy Fair Fair Slight Heavy
Four 42 F. 20-gauge sheet None Very Good Very good None None
Plioseal None Very Good Very good None None
Weeks None (Control) Heavy Poor Poor Slight Heavy
700 F. 20-gauge sheet None Fair Good None Medium
Plioseal None Fair Good Slight Medium
None (Control) Heavy Very Poor Very poor Heavy Heavy
Pliofilm in the Preservation of Florida Fruits and Vegetables 51
wrapped, at all temperatures. Pliofilm-wrapped fruit remained
in good edible quality at each temperature after softening twice
as long as unwrapped fruit.
Data in Table 12 show the efficiency of pliofilm in prevent-
ing shriveling, decay, and rind spotting; and in preserving taste
The optimum temperature for the holding of Haden mangos
was found to be 370 F. At this temperature the fruit retained
its good quality and flavor for a longer period and had less de-
cay and skin spotting than at higher temperatures.
Mangos in the plioseal were very attractive. The closely
fitting transparent wrapper permitted the attractive coloration
of the fruit to show to best advantage. The extension of time
required for the fruit to become soft and the prevention of dehy-
dration afforded by the pliofilm wrapper should make possible
the marketing of mangos over a longer period and in more dis-
tant areas than hitherto has been possible.
The rapid perishability of ripe peaches and the highly sea-
sonal character of this crop are problems of both grower and
shipper. Experiments with pliofilm on peaches were made in
an effort to preserve the initial freshness, color, texture and
taste during transit and on the retail stand, and to extend the
period during which peaches may be offered for sale in the
wholesale and retail markets, thus enabling stores to handle
them more effectively.
The tests included sheet wrapping with 40-gauge pliofilm
at several cold storage temperatures and the temperature of the
retail store, using four varieties of peaches during the 1940 sea-
son, followed by similar experiments using 20-gauge pliofilm
during the 1941 season. Jewel, Waldo, Angel, and Von Lutti-
chau peaches at both hard-ripe and soft-ripe stages of maturity
were used. One hundred wrapped and 100 unwrapped fruit at
both stages of maturity were placed in each of four tempera-
tures-370 F., 420 F., 540 F., and room temperature (70-900 F.).
They were packed in lugs, 100 fruit to the lug. These were
weighed and examined every three days. Since the results with
the four varieties were so nearly alike, only the results for the
Jewel variety will be presented here. Table 13 gives the per-
centage loss in weight of Jewel peaches in 40-gauge sheet wrap-
pers at 370 F., 42 F., 54 F., and room temperature (70-
TABLE 13-THE EFFECT OF PLIOFILM WRAPPERS ON THE PERCENTAGE LOSS IN WEIGHT OF JEWEL PEACHES OF DIFFERENT MATURITIES
AT 370 F., 42' F., 54 F. AND ROOM TEMPERATURE (70'-90' F.)
Percentage Loss in Weight After Days
Temperature Maturity Wrapper 3 6 9 12 15 18 24 30
3 6 9 12 15 18 24 30
Hard Ripe 40 gauge sheet 0.00 0.15 0.23 0.30 0.37 0.40 0.58 0.75
Hard Ripe None (Control) 0.47 0.89 1.32 2.72 3.20 3.80 4.30 5.60
370 F. Soft Ripe 40 gauge sheet 0.18 0.33 0.40 0.62 0.70 0.77 0.90 0.98
Soft Ripe None (Control) 0.52 1.02 1.30 3.05 3.75 4.10 4.40 5.92
Hard Ripe 40 gauge sheet 0.15 0.27 0.33 0.41 0.45 0.58 0.70 0.93
Hard Ripe None (Control) 0.58 0.97 1.50 2.90 4.10 4.30 5.10 5.90
42' F. Soft Ripe 40 gauge sheet 0.25 0.36 0.40 0.52 0.59 0.68 0.79 1.21
Soft Ripe None (Control) 0.63 0.98 1.60 2.71 4.70 4.92 5.50 6.10
Hard Ripe 40 gauge sheet 0.22 0.31 0.41 0.59 0.71 0.91 1.21
Hard Ripe None (Control) 1.70 2.04 3.75 3.90 4.40 5.90 -
54 F. Soft Ripe 40 gauge sheet 0.23 0.41 0.60 0.71 0.75 0.90 -
Soft Ripe None (Control) 1.92 2.20 3.70 3.82 4.51 All rotted hereafter
Room Temp. Hard Ripe 40 gauge sheet 0.40 0.60 0.82 0.97 1.06 1.21 -
(70-90' F) Hard Ripe None (Control) 4.72 6.07 8.20 8.74 -
Soft Ripe 40 gauge sheet 0.38 0.57 0.83 0.92 1.00 1.12 -
Soft Ripe None (Control) 4.90 6.34 8.16 All rotted hereafter
TABLE 14.-THE EFFECT OF PLIOFILM WRAPPERS ON THE SOFTENING, MARKETABILITY, DECAY AND SHRIVELING OF JEWEL PEACHES AT
i ime iin Marketable Percent Decay Amount Shriveling
Time Condition (Days) After After
Temperature Maturity Wrapper e(Days) After
to In Storage oval Two Four Two Four
Soften 1o Room
Soften oge ..oom Weeks Weeks Weeks Weeks
_e __ __ ,____ _... .._--__ T mp.
Hard Ripe 40-gauge sheet Removal 15 None 0 0 None Slight
37, F. Hard Ripe None (Control) 24 10 None 3 5 Slight Severe
Soft Ripe 40-gauge sheet 15 None 0 1 None Slight
Soft Ripe None (Control) 10 None 6 8 Slight Severe
Hard Ripe 40-gauge sheet Removal 36 10 0 3 None Slight
42o F. Hard Ripe None (Control) 14 20 3 4 10 Moderate Severe
Soft Ripe 40-gauge sheet 30 8 2 5 None Slight
Soft Ripe None (Control) 15 2 6 15 Moderate Severe
Hard Ripe 40-gauge sheet 10 18 6 5 4 Slight Slight
54, F. Hard Ripe None (Control) 5 10 3 20 26 Severe Very severe
Soft Ripe 40-gauge sheet 15 5 5 5 Slight Slight
Soft Ripe None (Control) 9 2 22 20 Severe Very severe
Hard Ripe 40-gauge sheet 9 12 6 ..- Slight Moderate
Room Temp. Hard Ripe None (Control) 3 5 -- 22 Severe Very severe
(700-90F.) Soft Ripe 40-gauge sheet 10 -- 8 Slight Moderate
Soft Ripe None (Control) 3 26 .. Severe Very severe
54 Florida Agricultural Experiment Station
900 F), with both soft-ripe and hard-ripe fruit. The data show
very little loss in weight of the pliofilm-wrapped peaches at any
of the temperatures; those not wrapped lost five to 30 times
more weight than the ones wrapped in pliofilm. Even after
30 days' storage the loss in weight of wrapped fruit at all tem-
peratures was as low as 1 percent. Wrapped fruit at this time
had the appearance of freshly picked fruit. The data also show
that temperature affected loss in weight, the lower temperature
giving smaller percentage loss. Soft-ripe fruit lost more weight
than hard-ripe fruit.
Table 14 compares wrapped with unwrapped Jewel peaches
as to time required for softening; time remaining marketable,
both during and after removal from storage; percent decay af-
ter two and four weeks; and amount of shriveling.
The results show that of the three temperatures the best
one for storing peaches is 42 F. Fruit held at 370 F., showed
physiological breakdown or darkening of the flesh after 10 days
in storage. This darkening became more severe with longer
periods of storage or after removal from storage. The rate of
decay and shriveling was higher at temperatures above 420 F.
Taking all factors into consideration, the results show 42 F., to
be the best temperature for peaches, both wrapped and not
Pliofilm retarded ripening and softening at all temperatures,
as shown in Table 14, and the life of the fruit was more than
doubled by the pliofilm wrappers. Wrapped fruit held up much
better and for a much longer period of time after removal from
storage to room temperature than that not wrapped. The per-
cent decay was considerably higher in the unwrapped fruit at
Similar results were obtained during the 1941 season using
20-gauge pliofilm on both Jewel and Elberta peaches. The loss
in weight was slightly higher in the fruit in the 20-gauge than in
that in the 40-gauge pliofilm, but did not noticeably affect the
general appearance of the fruit. The flesh of the peaches
stored at 370 F. became darkened after 10 days' storage, as was
true with those stored the previous season. The results again in-
dicated 42 F. was the best temperature for storing peaches and
showed that the 20-gauge as well as the 40-gauge pliofilm dou-
bled the time that peaches could be kept in a fresh condition.
A supplementary experiment was conducted to determine
the reaction of Jewel peaches to plioseal. Results were similar
Pliofilm in the Preservation of Florida Fruits and Vegetables 55
to those obtained when using 20-gauge sheet wrappers. The plio-
seal peaches were very attractive.
The investigation on pliofilm-wrapped avocados covered a
period of two seasons (1939-1941). During 1939-40, 40-gauge sheet
wrappers were used on several varieties each of the West Indian,
Fig. 16-Lula avocados after four months' storage at 420 F. Left,
wrapped in pliofilm; right, unwrapped.
56 Florida Agricultural Experiment Station
Guatemalan and hybrid types. Not less than three dozen fruit
of each variety were wrapped in 40-gauge pliofilm and an equal
number not wrapped and placed in each of three temperatures-
370 F., 420 F. and room temperature (70-800 F.). The fruit was
packed with excelsior in the regular avocado lugs. Losses in
weight and observations as to quality, texture, taste and percent
decay were recorded at regular intervals. Trapp, Waldin, Booth
8, Lula and Taylor varieties were used. These were picked in
the mature green, hard stage from the groves of the Sub-Tropical
Experiment Station, Homestead, and were shipped by express to
Gainesville, where they were placed at the various temperatures
within 24 hours.
Lula and Taylor-Loss in weight of Lula avocados at the
three temperatures over a nine-week period was from three
to 10 times more in unwrapped than in wrapped fruit. After
nine weeks the wrapped avocados at 370 F. had lost only 85
hundredths of 1 percent of their original weight. Loss in weight
was about the same for all varieties but differences were found
between the reaction of varieties to wrappers and temperatures.
Lula and Taylor varieties were held in good condition when
wrapped in pliofilm (Fig. 16). Best results were obtained at 420
F., when the keeping quality after removal to room temperature
also was considered. The fruit remained marketable longer at
370 F. but did not soften up normally when removed from this
TABLE 15.-COMPARISON OF THE Loss IN WEIGHT OF LULA AVOCADOS WRAPPED IN
40-GAUGE PLIOFILM WITH THOSE NOT WRAPPED.
Percentage Loss in Weight After Weeks
1 2 3 4 9
37* F. Sheet 0.14 0.21 0.26 0.33 0.85
(Control) 0.76 1.75 3.36 4.69 11.98
42 F. Sheet 0.13 0.23 0.38 0.49 0.97
(Control) 1.89 3.59 5.26 6.91 14.14
Room Sheet 0.21 0.86 1.36
(700-80 F.) None
(Control) 6.04 9.84
Pliofilm in the Preservation of Florida Fruits and Vegetables 57
temperature. Also the vascular bundles in the edible tissue had
a tendency to darken in the fruit held at 37' F.
At 420 F. pliofilm-wrapped fruit remained marketable from
two to three weeks longer than that not wrapped. The wrapped
fruit remained in good firm condition six weeks in cold storage
and from seven to 14 days after removal to room temperature (700
F.-800 F.), while unwrapped fruit remained in good condition
three to four weeks in cold storage and four to eight days after
removal to room temperatures.
Wrapped fruit which had been held at room temperatures
softened to an edible state after 10 to 18 days and remained
marketable for five to seven days after softening, while that not
wrapped softened in six to 14 days and remained marketable for
two and three days after softening. These results indicate a re-
tarding effect on the softening process by the pliofilm wrapper,
thus doubling the life of the fruit at ordinary room temperatures
(700 F. 800 F.).
Trapp and Pollock.-Similar results were obtained with
Trapp and Pollock varieties. These also reacted best at a tem-
perature of 42 F. as there was no darkening of the edible flesh at
this temperature. The pulp darkened after two weeks' storage
at 370 F. These varieties showed the same reactions at room tem-
perature as did the Lula and Taylor varieties.
Booth 8 and Waldin.-Booth 8 and Waldin varieties did not
react well to either cold storage temperatures or pliofilm wrap-
pers. By wrapping in pliofilm slight advantage was obtained in
the length of time the fruit remained marketable, and in the con-
dition of the fruit, but the results were not comparable with those
obtained with wrapped Lula and Taylor varieties.
The investigations were repeated the following season, 1940-
41, using 20-gauge sheet wrappers and the plioseal. In most cases
a slight advantage in the 20-gauge was observed over the 40-
gauge but the results so nearly duplicated those of the 40-gauge
that they are not given here. The plioseal had the added advant-
age of a more attractive appearance. It made a beautiful pack-
age, lending a glistening sheen to the already beautiful green
coloration of the fruit. The loss in weight was approximately
the same for the plioseal fruit as for that wrapped in 40-gauge
In general, the earlier varieties, which are mostly West In-
dians, did not react as well in pliofilm wrappers or cold storage
as the later varieties, such as Lula and Taylor. The latter varie-
58 Florida Agricultural Experiment Station
ties were very definitely benefited from the standpoint of taste,
quality, appearance, and marketability, by both the sheet-wrap
PRELIMINARY VEGETABLE INVESTIGATIONS
Vegetables have long been marketed in a more or less hap-
hazard way. For many years only the choicer grades were rough-
washed; the rest were packed into crates or hampers and ship-
ped to market, leaving the trimming and washing to the house-
wife. As competition became keener some shippers began wash-
ing and trimming the produce and wrapping it in paper to enable
them to identify their brands and to give the produce a better
eye-appeal on the wholesale markets and retail counters .
Since the public has become more sanitation-conscious, and
since there has been a trend to package food products in a more
attractive form, the vegetable producers and shippers are in-
terested in presenting their choice grades to the public in a condi-
tion that would have both good taste and quality.
Unfortunately, paper is sometimes used to cover poor quality.
The ideal wrapper for vegetables, therefore, is one that not only
will permit the produce to be kept longer in a fresh condition
but one which is transparent as well, permitting its freshness
and good quality to be easily observed. The properties of plio-
film make it an ideal vegetable wrapper in that it affords better
quality and offers the additional benefits of sanitation and at-
Pliofilm also permits the identification of brands, as brand
names can be easily printed on the film itself or printed inserts
can be seen readily through the wrappers.
The vegetables were placed under observation in the Horti-
cultural Laboratories and the Refrigeration Plant at the Experi-
ment Station in Gainesville. Temperatures of 370 F., 42' F., and
70' F. were used, approximating conditions for transit and stor-
age, as well as ordinary room temperature. The control tempera-
ture of 70 F. was chosen because it approximates the average for
the retail stores at the time most Florida vegetables are placed on
the market. The investigations were conducted during the sea-
sons of 1940 and 1941.
All of the vegetables except broccoli, Brussels sprouts, and
cauliflower, used in these investigations were obtained from the
Experiment Station gardens and were wrapped immediately
after packing. The others were obtained from commercial grow-
Pliofilm in the Preservation of Florida Fruits and Vegetables 59
ers and were wrapped within a few hours after harvesting. The
vegetables were not treated in any special manner before wrap-
ping except for the customary trimming, washing, grading and
sizing of commercial practice. The produce was wrapped at
room temperatures and either placed on slatted shelves in such a
position that it had free circulation of air or packed in crates,
boxes or hampers using the commercial size and pack arrange-
ments. Equal amounts of the produce were left unwrapped but
handled in exactly the same manner as those wrapped in pliofilm
to be used in evaluating the effects of the wrappers. The in-
dividual vegetables were weighed to a tenth of a gram ac-
curacy and the
20 weights of those in
each type of wrapper
"were averaged. The
CABBAGE packed produce was
weighed to /Vs pound
5 accuracy. Unless oth-
erwise specified, the
number of vegetables
Sto obtain an average
Percentage loss in
0a weight was never less
0 than 25 for any one
~ condition, 50 being the
number most general-
Figures in the ta-
5 bles and graphs are
averages of those veg-
S tables held on shelves
and weighed individ-
4 ually unless it is stat-
ed specifically that
0 2 4 6 8 10 12 these were weights of
Time in Storage (weeks commercial packs. Ob-
commercial packs. Ob-
Fig. 17.-Percentage weight loss of Cop- servation charts were
enhagen Market cabbage wrapped in 40- made on the perform-
gauge pliofilm and unwrapped. At cold
storage temperature of 37 F. 1 represents ance of the produce on
unwrapped and 2 wrapped cabbage; at re- shelves and in com-
tail stand temperature 3 represents unwrap- mercial packages. The
ped and 4 wrapped cabbage.
60 Florida Agricultural Experiment Station
commercial packages used in these experiments under each con-
dition of temperature and wrapping were not less than five
crates or hampers, unless otherwise stated. Sufficient samples
were used in the investigations with the various varieties of
vegetables to prevent individual variations from affecting the
results. At regular intervals the vegetables on the shelves and
in the commercial containers were examined for shriveling, color,
turgidity, texture, flavor, and palatability, and in some cases,
vitamin C content. Vitamin C (ascorbic acid) content was de-
termined by a modification of the method of Bessey and King
(5). Results of the experiments are recorded as numerical data,
supplemented by graphs, figures and photographs when possible.
Investigations with cabbage included a comparison of un-
wrapped cabbage with that wrapped in two gauges of pliofilm, 20
and 40, at temperatures of 370 F and 70 F. Observations were
made on the keeping quality and loss in weight of the cabbage on
shelves and in commercial hampers. Copenhagen Market cabbage
not wrapped lost approximately 15 to 20 times more weight than
that wrapped in the 40-gauge pliofilm at 370 F., while that not
wrapped and held at 70 F. lost 20 to 25 times more weight than
that wrapped in 20- and 40-gauge pliofilm (Table 16). The effect
of the wrappers in preventing loss in weight becomes even
more accentuated as length of storage increases, as shown in
Table 17 gives the condition of the cabbage in commercial
hampers at various intervals as to quality and appearance.
Changes in color were noted. Most outstanding was the preser-
vation of the green color (chlorophyll) in the cabbage. That
wrapped in pliofilm changed only slightly in color throughout
the whole period, while that not wrapped turned brownish after
a few days. The condition of texture was recorded at regular in-
tervals, judged as to freshness and physical quality. Pliofilm
was outstanding in holding the cabbage in a state of garden fresh-
ness as compared with that not wrapped, which soon became
shriveled and dry (Fig. 18). Flavor and texture were measured
by several individuals tasting both fresh and cooked samples,
and the pliofilm-wrapped cabbage was found to be tastier and
of much better flavor than that not wrapped. Wrapped cabbage
kept well at both temperatures, though it kept in a better condi-
tion for a longer time at the lower temperature.
TABLE 16.-COMPARISON OF PERCENTAGE Loss IN WEIGHT OF PLIOFILM-WRAPPED AND UNWRAPPED COPENHAGEN MARKET CABBAGE AT
370 F. AND 700 F.
Percentage Loss in Weight After Days
8 16 23 37 44 51 58 65 71 79
37' F. 40-gauge sheet 0.27 0.49 0.66 1.09 1.31 1.55 1.86 2.03 2.26 .
None (Control) 7.08 12.06 15.12 21.60 24.18 26.61 29.06 30.09 34.35
3 6 9 12 15 18 21 24
20-gauge sheet 0.16 0.36 0.56 0.80 1.04 1.58 1.60 2.13
70' F. 40-gauge sheet 0.19 0.34 0.56 0.65 0.88 1.06 1.23 1.33
None (Control) 3.41 7.45 10.96 16.84 19.56 23.11 24.54 27.90
62 Florida Agricultural Experiment Station
Fig. 18.-Copenhagen Market cabbage after five weeks' storage at
370 F. (left) wrapped in 40-gauge pliofilm and (right) unwrapped.
After eight and 23 days several dozen heads unwrapped and
wrapped in 40-gauge pliofilm were removed from cold storage
(370 F.) to retail stand temperature of 700 F. That wrapped held
up splendidly and was still marketable four weeks after removal,
while that not wrapped, having been already shriveled, became
more shriveled and discolored and after a few days was un-
There was very little rotting of either the wrapped or un-
wrapped cabbage. It was only after five or six weeks that rotting
occurred at all and then only slightly at 700 F.
After 154 days' storage at 370 F. the pliofilm-wrapped cabbage
was still edible, and vitamin C determinations were made on the
tissues. The heads protected with 40-gauge pliofilm wrappers
were found to contain 26.9 milligrams of ascorbic acid per 100
gram sample, as compared with 12.6 mg. per 100 grams for the
controls not wrapped. Fresh cabbage has a value of approxi-
mately 40.5 mg. per 100 grams. The preservation of vitamin C
during storage seems to be linked directly with the degree of
freshness that is maintained in the plant tissues.
Lettuce of the Iceberg type (Imperial 44) was wrapped in
20- and 40-gauge pliofilm sheets and placed on shelves, together
with an equal number not wrapped, and held at 370 F. and 700
F. Lettuce was also packaged in folded but not sealed bags of
120-gauge (P4) pliofilm. Three crates, each containing 12 heads,
TABLE 17.-EFFECT OF PLIOFILM WRAPPERS ON COLOR, TEXTURE AND PALATABILITY OF CABBAGE AT 37 F. AND 700 F.
Condition of Cabbage After Days
8 23 44 58 71
40-gauge Color Green Green Green Pale green Pale green
sheet Texture Very good Very good Good Good Good
Palatability Very good Very good Good Good Good
370 F. Color Pale green Yellow Browning Brown --
(Cold None Texture Good Fair Fair Poor -
Storage) (Control) Palatability Good Stale Very stale Poor
3 9 15 21 30
20-gauge Color Green Green Green Green Pale green Q
sheet Texture Very good Very good Good Good Good
Palatability Very good Very good Very good Very good Good
(Retail 40-gauge Color Very green Very green Green Green Green
Stand) sheet Texture Very good Very good Good Good Good
Palatability Very good Very good Very good Very good Good
Color Pale green Browning Brown Brown ---
None Texture shriveled Shriveled Shriveled Very dry .-
(Control) Palatability Good Fair Poor Poor --
TABLE 18.-EFFECT OF PLIOFILM WRAPPERS ON Loss IN WEIGHT OF ICEBERG LETTUCE (IMPERIAL 44) AT 370 F. AND 70' F.
Percent Loss in Weight After Days
3 6 9 12 15 18 21 24 27
37, F. 20-gauge sheet 0.13 0.23 0.32 0.34 0.39 0.42 0.57 0.68 0.70
(Cold Storage) None (Control) 3.81 7.05 9.03 10.12 12.38 12.94 14.99 15.97 17.23
70 F. 20-gauge sheet 0.33 0.70 1.08 .
(Retail Stand) None (Control) 6.73 11.78 17.42 26.57 ..
TABLE 10.-EFFECT OF PLIOFILM WRAPPERS ON COLOR, TEXTURE AND PALATIBILITY OF ICEBERG LETTUCE AT 37' F. AND 70o F.
Condition of Lettuce After Days
3 6 12 18
20-gauge sheet Color Green Green Green Pale green
Texture Very good Good Good Good
37 F. Palatability Very good Good Good Good
(Cold Storage) Color Green Green Pale green Brown
None (Control) Texture Good Fair Fair Poor
Palatability Good Fair Fair Poor
20-gauge sheet Color Green Green Pale green Pale green
Texture Good Good Good Fair
70t F. Palatability Good Good Fair Fair
Color Green Pale green Brown Brown
None (Control) Texture Fair Fair Poor Poor
Palatability Fair Poor Poor Poor
Pliofilm in the Preservation of Florida Fruits and Vegetables 65
were wrapped in each of the different types of wrappers and
three crates unwrapped were placed also at each temperature,
370 F. and 70 F. At either temperature heads not wrapped lost
15 to 25 times more weight than those wrapped in 20-gauge
film (Table 18). Figures for loss in weight are not shown for
the 40-gauge wrapper, which is slightly more efficient in re-
taining moisture than the 20-gauge but not as economical in ma-
terial. The lettuce held in the 120 P4 bag which was not sealed
but folded lost approximately the same amount of weight as that
in the 40-gauge wrapper. The percentage weight loss of the
protected lettuce was one-twentieth as much as that not wrapped.
Quality and appearance of the lettuce were noted at regular
intervals. In Table 19 color, texture and taste of lettuce in
wrappers and bags at 370 F. and 700 F. are recorded. Color
changed but little in wrapped lettuce, while loss in color was
rapid in that not wrapped. Here, as with cabbage, the green
chlorophyll coloring was preserved by pliofilm. The wrapper
was very efficient in preserving good texture, especially at the
lower temperatures. The good flavor also was preserved by the
wrapper at 370 F., even after 30 days' storage, and that at room
temperature held the taste of fresh lettuce for 10 days, after
which time palatability declined. That not wrapped held its
color, taste and texture only 12 days at 370 F. and about five days
at 70 F., after which time it was brownish, shriveled and stale.
Lettuce kept much better in 20-gauge pliofilm wrappers than
in either 40-gauge wrappers or 120-gauge pliofilm bags. The
lettuce kept much better in bags which were folded, but not air-
Florida Pascal celery was wrapped in various ways in 20-
gauge sheet-wrapper over all; stretch-wrapped three-fourths of
the way up the stalk, with the top of the pliofilm fastened with a
rubber band, allowing the tops to protrude; in bags made of 120
N2 film to fit a stalk of celery, fastened at the top with a rubber
band, also allowing the tops to protrude. (Fig. 19). One dozen
stalks were packed in crates and two crates of each type of
wrapped and unwrapped celery were placed at both 37' F. and
Table 20 gives the percentage loss in weight of celery in the
various types of pliofilm protection held at the two temperatures.
The data show that the most efficient methods of packaging were
the 20-gauge over-all wrapper over-all plioseal which allowed for
TABLE 20.-EFFECT 0 PLIOFILM WRAPPERS ON Loss IN WEIGHT OF FLORIDA PASCAL CELERY AT 370 F. AND 700 F.
Percent Loss in Weight After Days
3 6 9 12 15 18 21 24 4
37' F. 20-gauge sheet 0.05 0.12 0.30 0.32 0.36 0.43 0.55 0.58
(Cold Storage Stretch-wrap 5.57 9.11 11.66 12.58 14.75 16.70 19.93 22.00
120-gauge bag 5.20 8.86 10.80 11.26 13.55 15.20 18.40 20.10
None (Control) 6.38 17.06 22.70 26.46 31.24 35.25 39.98 42.32
700 F. 20-gauge sheet 0.28 0.65 1.19 1.89 .... ..
(Retail Stand) Stretch-wrap 9.48 20.83 29.22 32.38 37.32 ......
120-gauge bag 9.33 19.35 27.63 33.72 35.99-
None (Control) 10.20 24.99 38.70 45.13 52.10.
TABLE 21.-EFFECT OF PLIOFILM WRAPPERS ON COLOR, TEXTURE AND PALATABILITY OF CELERY (FLORIDA PASCAL) AT 370 F. AND 700 F.
Tempera- Condition of Celery After Days
ture 3 6 9 12 18 30
Color Green Green Green Green Green Green
20-gauge Texture Very good Very good Very good Very good Very good Very good "
sheet Palatability Very good Very good Very good Very good Very good Very good
37 F. Strec Color Green yellow Green Green Pale green Pale green Browning
3CoF. Street Texture Very good Very good Good Good Good Good
tord wrap Palatability Very good Very good Good Good Good Good
Color Green Green Green Pale green Pale green Browning
120-gauge Texture Good Good Good Good Fair Fair
bag Palatability Good Good Good Good Fair Fair
None Color Yellow Browning Browning Brown Brown
None Texture Good Fair Fair Poor Poor -
oro Palatability Good Fair Fair Poor Poor -
20-g e Color Green Green Green Green Pale green Pale green
20-gauge Texture Very good Very good Very good Good Good Fair
see Palatability Very good Very good Very good Good Good Fair
70 F St h Color Green Green Pale green Pale green Yellow Brown
(Retail wra Texture Good Good Good Good Fair Poor
Stand) Palatability Good Good Good Good Fair Poor
Color Green Green Green yellow Green yellow Yellow Brown
120-gauge Texture Good Good Good Good Fair Poor
"bag Palatability Good Good Good Fair Fair Poor
None Color Yellow Browning Brown Brown
(Control) Texture Fair Shriveling Shriveled Dried
Palatability Fair Fair Poor Poor .-
68 Florida Agricultural Experiment Station
comparatively small loss in weight from any part of the celery,
while the three-fourths stretch-wrap and bags permitted loss in
weight and subsequent drying of the upper leaves. The figures
show that the weight loss of celery, under refrigeration, was much
less than of that held at the temperature of the retail stand.
Changes in color, texture and taste were judged with refer-
ence to the original harvest condition and these observations are
presented in Table 21. Most outstanding was the preservation of
the original green and yellow coloration by the wrapper. The
Fig. 19.-Florida Pascal celery showing four ways of wrapping in
pliofilm. Left to right: Plioseal (stretch-wrap over all), stretch-
wrapped three-fourths of the way up, in 120-gauge bag, and wrapped in
20-gauge sheet over all.
Pliofilm in the Preservation of Florida Fruits and Vegetables 69
leaves under the wrapper changed very little while those of the
unwrapped controls shriveled and browned within a few days;
however, by protecting the stalks with a bag or stretch-wrap, the
original coloration of the projecting leaves was maintained for a
longer period than with the control. Texture of the wrapped
celery was far superior to that of the unwrapped. Turgidity and
freshness of that wrapped was equal to that freshly harvested,
even after 18 days at 370 F. and six days at 700 F. The taste of
wrapped celery was that of the field-fresh product and its flavor
was retained throughout the period of observation, while the un-
wrapped celery became stale after a few days at 70 F. and after
six days at the lower temperature.
The method of wrapping giving the best results was found to
be the 20-gauge sheet over-all wrapper. While not as attractive
as the stretch-wrap and bag, it was more efficient in all respects
than either of these. The results of these trials point toward the
use of thinner gauges of pliofilm with the entire mass enclosed
within, permitting the color, texture and taste of the whole celery
stalk to remain fresh for a longer time. Celery in pliofilm wrap-
pers at retail stand temperature is much superior to that not
wrapped, and the results indicate that wrapped celery will re-
main fresh for a longer time at lower temperatures.
The experiment was repeated using the Golden Self-Blanch-
ing variety and similar results were obtained.
California Wonder peppers were wrapped in 20-gauge sheet
wrappers and the plioseal and placed at 370 F. and 70 F. Also,
20-gauge liners were made to fit containers holding several dozen
peppers. The liners were made to fold over at the top but were
not sealed. Records were taken of loss in weight, changes in
color, texture and taste on the individually wrapped samples
held on shelves and in crates and on those in lined crates.
Table 22 gives a comparison of the loss in weight of the pep-
pers packaged in the various ways with those not protected by
pliofilm, at 370 F. and 700 F. The data show that the unwrapped
peppers lost eight to 10 times more weight than those in either
the plioseal or 20-gauge sheet-wrapper. Preventing excessive
loss in weight in peppers is very important in that the morpholo-
gical structure of the pepper is such as to allow excessive drying
within a short time, causing peppers to be short-lived. Tables
22 and 23 show that the salable life of peppers was lengthened
TABLE 22.-EFFECT OF PLIOFILM WRAPPERS ON PERCENTAGE LOSS IN WEIGHT OF CALIFORNIA WONDER PEPPERS AT 37 F. AND 70' F.
Temperature Wrapper Percentage Loss in Weight After Days
3 6 9 12 15 18 24 30
37 F. 20-gauge sheet 0.07 0.24 0.42 0.49 0.55 0.64 0.81 0.98
(Cold Storage) None (Control) 1.02 2.33 3.40 4.13 4.95 6.13 7.31 8.56
700 F. 20-gauge sheet 0.32 0.83 1.24 1.53 1.80 2.25 2.82 2.92
(Retail Stand) Plioseal 0.31 0.75 1.24 1.29 1.46 1.75 2.34 2.67
None (Control) 3.30 6.24 9.92 12.22 15.34 18.23 21.86 22.00
TABLE 23.-EFFECT OF PLIOFILM WRAPPERS ON COLOR, TEXTURE AND PALATABILITY OF CALIFORNIA WONDER PEPPERS AT 370 F. AND 70 F.
Condition of Peppers After Days
Temperature Wrapper 6 9
3 6 9 12 18
Color Deep green Deep green Deep green Deep green Green
20-gauge Texture Very good Very good Very good Very good Very good
sheet Palatability Very good Very good Good Good Good
37" F. Color Deep green Deep green Deep green Deep green Green
(Cold Plioseal Texture Very good Very good Very good Very good Very good
Storage) Palatability Very good Very good Very good Very good Very good
None Color Green Green Green-red Red Red
(Control) Texture Good Fair Fair Poor Poor
Palatability Good Fair Fair Poor Poor
Color Deep green Deep green Green Green-red Green-red Z.
20-gauge Texture Very good Very good Good Good Good
sheet Palatability Very good Very good Good Good Good
700 F Color Deep green Deep green Deep green Green Green
(Retail Plioseal Texture Very good Good Good Good Good
Store) Palatability Very good Good Good Good Good
eNone Color Green Green-red Red Red Red
(Cntrol) Texture Sit. shrivelingShriveled Shriveled Badly shriv'dDried
onroPalatability Fair Fair Poor Poor Poor
Pliofilm in the Preservation of Florida Fruits and Vegetables 71
two weeks by the pliofilm wrapping. The plioseal on peppers
was more attractive and economical and slightly more efficient
in preventing weight loss than the 20-gauge sheet-wrapper (Fig.
The original green color was well preserved by the pliofilm
wrapper. No change in color of the peppers occurred after 15
days (Table 23), while those not wrapped changed color six
days after harvesting. Texture of peppers in both plioseal and
sheet-wrapper was very good throughout the 30-day period,
while those not wrapped lost their turgidity and freshness after
the first few days. Here again texture of the produce was best
maintained by refrigeration of both the wrapped and unwrap-
ped peppers. The taste of the wrapped peppers was good
throughout the storage period, while those not wrapped became
stale after several days.
Fig. 20.-California Wonder peppers after two weeks at 70 F. (left)
unwrapped and (right) pliosealed.
72 Florida Agricultural Experiment Station
After 23 days' storage at 370 F. and 70 F. vitamin C (as-
corbic acid) determinations were made on the edible tissues.
At this time pliofilm-wrapped peppers stored at 370 F. had 9.3
milligrams more ascorbic acid per 100 grams than unwrapped
peppers. Those at 700 F. contained 36.4 milligrams more ascor-
bic acid per 100 grams than those not wrapped. Fresh peppers
Fig. 21.-Straight 8 cucumbers after two weeks' storage at 700 F.
(left) in the plioseal (stretch-wrap) and (right) wrapped in 20-gauge
Pliofilm in the Preservation of Florida Fruits and Vegetables 73
were found to contain from 100 to 200 milligrams per 100 grams.
Crate liners made from 20-gauge pliofilm, folded but not seal-
ed, were not as efficient as the individual wrappers. Loss in
weight was about the same for both, but decay was greater in
the liner, due to the fact that "nesting" occurred, which is not
possible when the individual wrapper is used.
Tests with several varieties of cucumbers included sheet-
wrapping and the plioseal, with observations at several cold
storage temperatures and the temperature of the retail store.
The cucumbers were packed in small hampers and each cucum-
ber was weighed individually to obtain the average percentage
weight losses. Table 24 gives the percentage loss in weight at
regular intervals of Straight 8 cucumbers in 20-gauge sheet wrap-
pers, plioseal, and those not wrapped at 370 F. and 70' F. The
data show very little difference between types of wrappers
used, but indicate that cucumbers not wrapped lost from 15 to
40 times more weight than those wrapped. Even though ex-
cessive moisture loss from cucumbers does not necessarily af-
fect their edibility to the degree found in leafy vegetables, it
always causes a certain degree of wilting and shriveling, ren-
dering them decidedly less attractive to the buyer and consumer.
Color, texture and taste were affected (Table 25). The color
was unchanged in the wrapped cucumbers throughout the period
of observation but turned pale and yellow after a few days when
the cucumbers were not wrapped. The plioseal gives an attrac-
tive gloss to the cucumber, accentuating its deep green color
(Fig. 21). The texture and taste of the wrapped cucumbers were
far superior to those not wrapped. Pliofilm preserved the ori-
ginal quality of the cucumbers in all respects for eight to 10 days
and in very good condition up to two weeks at 70 F. and nearly
double that time at 370 F.
The experiment was duplicated using the Colorado variety.
Results were obtained almost identical with those presented
above for the Straight 8 variety.
Two varieties of eggplant (Florida High Bush and Fort
Myers Market) were wrapped in 20-gauge sheet-wrappers and
the plioseal. These were compared with eggplants not wrapped
and held at both refrigeration and retail store temperatures. The
TABLE 24.-EFFECT OF PLIOFILM WRAPPERS ON Loss IN WEIGHT OF CUCUMBERS (STRAIGHT 8) AT 370 F. AND 70 F.
Percent Loss in Weight After Days
Temperature Wrapper 14 21 28
37 F. 20-gauge sheet 0.13 0.23 0.32
(Cold St ) Plioseal 0.24 0.40 0.59
(Cold Storage) None Control 7.52 8.66 -
3 6 9 12 15 18 21 24
70, F 20-gauge sheet 0.24 0.48 0.78 0.92 1.23 1.48 1.35 1.43
(Retail Stnd) Plioseal 0.24 0.42 0.69 0.88 1.13 1.51 1.87 2.22 .
detail and) None (Control) 6.07 10.41 11.89 13.87 17.18 19.43 22.29 23.30
TABLE 25.-EFFECT OF PLIOFILM WRAPPERS ON COLOR, TEXTURE AND PALATABILITY OF CUCUMBERS (STRAIGHT 8) AT 370 F. AND 700 F.
Condition of Cucumber After Days
Temperature Wrapper 7 14 21
Color Deep green Deep green Green
20-gauge sheet Texture Very good Very good Good
Palatability Very good Very good Good
37 F. Color Deep green Deep green Green
(Cold Storage) Plioseal Texture Very good Very good Good
Palatability Very good Very good Good
Color Light green Yellowing Yellow
None (Control) Texture Slightly Shriveled Dried up
Palatability Fair Poor Very poor
3 6 9 12 15 18
Color Dark green Dark green Dark green Green Green Green
20-gauge sheet Texture Very good Good Good Good Good Good
70* F. Palatability Very good Very good Very good Very good Very good Very good
(Retail Stand) Color Dark green Dark green Dark green Dark green Green Green
Plioseal Texture Very good Good Good Good Good Good
Palatability Very good Very good Very good Good Good Good
Color Green Dull green Dull green Dull green Yellow greenYellow green
None (Control) Texture Shriveled Poor Poor Poor
Palatability Fair Fair Poor Poor Poor Poor
Pliofilm in the Preservation of Florida Fruits and Vegetables 75
eggplants were packed in bushel hampers and individual weights
taken were averaged to give the percentage loss in weight.
Table 26 gives the percentage loss in weight of Florida High
Bush eggplant at 370 F., 42' F., and 700 F., wrapped in 20-gauge
sheet wrappers and the plioseal compared to those not wrapped.
The data show that the unwrapped eggplants lost 10 to 20 times
more weight under refrigeration, and six to 10 times more weight
at retail stand temperature, than did the eggplants in the plioseal
or 20-gauge sheet-wrappers. The optimum temperature for stor-
age was found to be 370 F. but the salable life of eggplants was
doubled at all temperatures when wrapped. Color, texture, and
taste were recorded at regular intervals (Table 27). The lus-
trous purple color of fresh eggplant was preserved by wrapping
and was accentuated by the attractive gloss of the plioseal. Its
freshness, turgidity, texture, and taste remained equal to that
of fresh eggplant for 14 days and in a marketable state for 21
days at 370 F. and seven days at 70' F.
Results obtained with the Fort Myers Market variety were
similar to those presented above for the Florida High Bush va-
All tomatoes used in the 1940 wrapper experiments were of
the Marglobe variety. The fruits were picked at three different
stages of maturity: "Mature green", fruit which had attained
full growth but had not begun to show color; "turning pink",
fruit which had begun to show a pink color; and "red ripe",
fully ripe and colored but firm, sound fruit. One hundred fruit
of each maturity were wrapped with 40-gauge pliofilm, packed
in lugs and placed at each of the following temperatures: 370 F.,
42 F., 540 F., 650 F., and room temperature (700-90 F.), and an
TABLE 26.-EFFECT OF PLIOFILM WRAPPERS ON Loss IN WEIGHT OF FLORIDA HIGH
BUSH EGGPLANT AT 370 F., 420 F., AND 700 F.
Percentage Loss in Weight After Days
Wrapper 7 14 21 28
37 F. 20-gauge sheet 0.14 0.31 0.37 0.45
(Cold Storage) Plioseal 0.18 0.37 0.68 0.89
None (Control) 3.87 5.60 7.00 8.92
42* F. 20-gauge sheet 0.16 0.36 -
(Cold Storage) Plioseal 0.13 0.41 0.66 -
None (Control) 3.38 6.72 -
70 F. 20-gauge sheet 0.62 1.25 -
(Retail Stand) Plioseal 0.95 1.90 -
None (Control) 6.16 10.78 13.36 -
TABLE 27.--EFECT OF PLIOTILM WRAPPERS ON COLOR, TEXTURE AND PALATABILITY OF FLORIDA HIGH BUSH EGGPLANT AT 37 F. AND 70 F.
Temperature Wrapper Condition of Eggplant After Days
7 14 21 28
Color Deep purple Deep purple Deep Purple Deep purple .
20-gauge sheet Texture Very good Very good Good Good
Palatability Very good Very good Good Good
37 F. Color Deep purple Deep purple Purple Purple c.
(Cold Storage) Plioseal Texture Very good Very good Very good Good
Palatability Very good Very good Very good Good
Color Purple Purple Brownish
None (Control) Texture Fair Fair Shriveled -
Palatability Fair Fair Poor ---
Color Deep purple Deep purple Purple Purple
20-gauge sheet Texture Very good Very good Good Fair
Palatability Very good Very good Good Fair
70' F. Color Deep purple Deep purple Purple Purple
(Retail Store) Plioseal Texture Very good Very good Good
(eai orePalatability Very good Brownish Fair
Color Light purple Good Brown ---
None (Control) Texture Fair Poor Poor
Palatability Fair Poor Poor
Pliofilm in the Preservation of Florida Fruits and Vegetables 77
370F 420F. 5uLF. 650F.
S2 3- 4 2 3 I 2 3 I Z T-7 F
No Wrap [ Wrapped 40 Gauge Pliofilm
Fig. 22.-Percentage decay of tomatoes picked when showing pink
coloration and stored four weeks at temperatures of 370 F., 42 F., 54" F.
and 65 F.
equal number were left unwrapped for comparison at each tem-
perature. The fruit was inspected daily throughout the storage
period. The percentage decay was calculated and is presented in
graphical form for the "turning pink" stage of maturity in
Figure 22. An important result of the wrapping, shown by the
graphs, is that the percentage decay was lower at all tempera-
tures in wrapped tomatoes than in those not wrapped. It will
be noted that the rate of decay was directly proportional to the
temperature used, the lower temperature having the advantage
over the higher temperature in all cases. However, it may be
seen that this advantage of low temperature was not so great
in the case of the wrapped fruit as of that not wrapped. At
all times the wrapped fruit was in much better condition from
the standpoint of firmness, turgidity and flavor than the unwrap-
ped fruit of the same stage of maturity stored at the same tem-
'peratures (Fig. 23).
It was noted that, in general, wrapped tomatoes ripened
more slowly than unwrapped ones, which may be a contributing
factor to the longer holding of the wrapped fruits. Thus wrap-
ping in pliofilm would permit the tomatoes to be picked and
shipped in a more mature stage than is now practicable. Wrap-
ped tomatoes picked in the green and pink stages required double
the time to reach full maturity that was required for those not
78 Florida Agricultural Experiment Station
wrapped. Tomatoes picked when red ripe and wrapped or
those ripened in the wrapper remained in a good firm condition
twice as long as did the unwrapped tomatoes.
The wrapping experiment on Marglobe tomatoes was re-
peated during the 1941 season, using the same temperatures,
maturities and quantities of fruit except that 20-gauge was sub-
stituted for 40-gauge pliofilm sheet-wrap. Moisture loss, color,
quality and taste were recorded at regular intervals. Table 28
gives the percentage loss in weight of Marglobe tomatoes of the
three different maturities of fruits wrapped in 20-gauge pliofilm
compared to the loss in those not wrapped at cold storage and re-
tail stand temperatures. Those not wrapped lost 10 to 20 times
more weight than those in 20-gauge pliofilm at 370 F. and five
to eight times more weight at 500 F. The fruit under 40-gauge
pliofilm lost even less than those wrapped in 20-gauge. In all
other respects no differences could be detected between the re-
sults obtained by use of 20 and 40-gauge pliofilm.
Table 28 also shows that those tomatoes in the pink stage
of maturation (turning pink) lost more weight than either the
Fig. 23.-Marglobe tomatoes picked when showing pink coloration,
after four weeks' storage at 54 F. Top fruit were wrapped in 40-gauge
pliofilm, bottom unwrapped.
TABLE 28.-PERCENTAGE Loss IN WEIGHT OF MARGLOBE TOMATOES OF DIFFERENT MATURITIES AS AFFECTED BY Pt.IOFILM WRAPPERS AT
37 F. AND 650 F.
Percentage Loss in Weight After Days
Temperature Wrapper Maturity
4 7 10 13 16 19 22 28
20-gauge sheet Mature green 0.01 0.10 0.15 0.18 0.27 0.31 0.42 0.51
37o F, 20-gauge sheet Pink 0.13 0.17 0.29 0.34 0.45 0.53 0.60 0.72
20-gauge sheet Red 0.10 0.15 0.18 0.25 0.32 0.39 0.50 0.61
None (Control) Mature green 0.83 1.62 2.53 3.07 3.99 4.66 5.62 6.40
None (Control) Pink 1.18 2.33 3.37 3.61 4.34 4.99 5.80 6.95
None (Control) Red 0.99 1.98 2.37 2.75 3.24 3.42 3.51 -
65 F. 20-gauge sheet Pink 0.28 0.67 0.95 1.23 1.50 1.76 1.89 -
(Retail Stand) None (Control) Pink 1.73 3.64 4.85 7.11 9.67 -
80 Florida Agricultural Experiment Station
less mature or more mature throughout the entire time. Those
picked in the green stage showed less weight loss than those
picked in either the pink or red stage of maturity.
Full grown bulb onions (Grano) were used. Onions wrap-
ped in various types of pliofilm were compared with those un-
wrapped at different temperatures. Taste, texture, color, weight
loss and vitamin C content were determined and recorded at
various intervals. One hundred onions were wrapped in 20-
gauge sheets, 100 pliosealed, and 100 left unwrapped for each
of the three temperatures. These were packed in small crates
and weighed individually to obtain averages. Percentage weight
loss of the unwrapped onions was approximately five times more
than that in the 20-gauge wrapper and seven times more than
that in plioseal at the two lower temperatures and more than
three times greater than either at 70 F. (Table 29).
Observations were made on quality, taste and appearance
of the onions at intervals. Pliofilm was outstanding in holding
the onions in a state of harvest freshness and color, as com-
pared with those not wrapped which soon became shriveled and
dry. Little difference was noted in the effect of temperature
and wrappers on the taste of the onions until the latter part of
the experiment, when the wrapped onions were found to be of a
much better flavor than those not wrapped. The outer two
sections of the unwrapped onions became tough, leathery and
discolored after six weeks' storage at 370 F. and 42' F. and the
outer skin dried and scaled off. Those in the pliofilm wraps
showed no distinguishable change in texture at these tempera-
tures throughout the entire experiment. The section of the ex-
periment at 700 F. was discontinued because of excessive sprout-
ing after one month. Small roots formed at lower temperatures
after 12 weeks on a large number of onions.
Vitamin C content of the onions was determined after 12
weeks at 420 F. Four determinations were made in duplicate
for each wrap and for the unwrapped control. Since the mois-
ture loss often exceeds the rate at which vitamin C is lost, re-
sults were calculated on initial weights. These determinations
were averaged and expressed as milligrams of ascorbic acid per
100 grams of sample. Vitamin C content of fresh bulb onions
is nine milligrams per 100-gram sample. Onions at 420 F. in
the plioseal were found to contain eight milligrams per 100-
Pliofilm in the Preservation of Florida Fruits and Vegetables 81
gram sample and 20-gauge sheet-wrappers 7.6 milligrams per 100
grams after 12 weeks. Unwrapped onions were found to con-
tain only 2.8 milligrams per 100-gram sample. This represents
a loss of nearly 69 percent of the total ascorbic acid content for
the unwrapped as compared with 11 and 15 percent loss in the
pliofilm wrapped onions over the 12 week period.
TABLE 29.-EFFECT OF PLIOFILM WRAPPERS ON Loss IN WEIGHT OF ONIONS
(GRANO) AT 37' F. AND 70' F.
Percent Loss in Weight After Weeks
1 2 3 4 5 6 12
20-gauge sheet 0.15 0.24 0.44 0.53 0.62 0.83 2.31
370 F. Plioseal 0.03 0.05 0.13 0.23 0.33 0.46 2.12
(Cold Storage) None (Control) 0.77 1.16 2.15 2.87 3.91 4.80 12.35
20-gauge sheet 0.23 0.44 0.57 0.71 0.84 1.25 3.14
42 F. Plioseal 0.18 0.28 0.37 0.40 0.49 0.62 2.12
(Cold Storage) None (Control) 0.76 1.68 2.64 3.60 4.97 6.29 15.36
20-gauge sheet 0.34 0.61 1.01 1.50* -
70 F. Plioseal 0.22 0.34 0.47 0.74* -
(Retail Store) None (Control) 0.95 1.96 3.66 5.62* -
*Discontinued because of sprouting.
Fresh corn on the cob always has been a highly perishable
commodity and as such has never gained deserved popularity
with the Florida grower. Corn marketed locally or shipped
to Northern markets does not always have the uniform quality
The 20-gauge pliofilm sheet-wrapper and the plioseal were
used in an experiment designed to improve the methods of mar-
keting fresh corn. In preparation, fresh ears of Golden Cross
Bantam corn were husked, silked, trimmed, washed and pre-
cooled with ice water. One hundred ears in each type of wrap-
per and an equal number of unwrapped controls were placed
at temperatures of 370 F. and 70 F. The ears were placed
in lugs. Observations were made on shrinkage, taste and ap-
pearance on alternate days. The ears were weighed individu-
ally and the weights averaged to obtain the percentage weight
Table 30 shows the weight loss of the samples after varying
periods. It is of interest to note the exceptionally large per-
centage weight loss of the ears at both temperatures not wrapped
in pliofilm after a short period of time. This was accompanied
TABLE 30.-EFFECT OF VAPIO-S TYPES OF PLIOFILM WRAPPERS ON THE Loss IN WEIGHT OF GOLDEN CROSS BANTAM SWEET CORN AT 370
F. AND 700 F.
Percentage Loss in Weight After Days
2 6 8 11 13 18 21 23 4
20-gauge sheet 0.10 0.29 0.43 0.63 0.72 1.03 1.33 1.44
37 F. Plioseal 0.12 0.33 0.42 0.65 0.73 0.98 1.23 1.42
*Unhusked (Control) 3.42 6.50 8.41 10.40 13.20 17.25 20.17 22.30
"**Husked (Control) 4.00 10.20 13.80 17.10 19.60 25.80 29.20 32.60
20-gauge sheet 0.35 1.31 1.92 2.40 2.84 4.94 6.16 6.86
Plioseal 0.27 1.18 1.82 2.25 2.39 3.50 4.30 4.90
70 F. Unhusked (Control) 5.30 15.22 22.60 27.20 30.28 36.60 39.48 46.18
Husked (Control) 6.63 17.47 27.21 30.67 34.05 53.84 58.63 62.51 ei
*Unhusked (Control)-Corn from which husk has not been removed. No pliofilm wrapper.
"**Husked (Control)-Corn from which husk has been removed. No pliofilm wrapper.
Pliofilm in the Preservation of Florida Fruits and Vegetables 83
by an equally rapid loss of flavor and appearance. Within a
day the loss in flavor of the unwrapped corn at 70 F. was plain-
ly distinguishable, as was the case after two days at the lower
The efficiency of both types of pliofilm wrappers in retain-
ing both the original weight and flavor was indeed remarkable.
Change in flavor of wrapped corn at room temperature was de-
tectable after five days, while at lower temperatures it retain-
ed its original flavor for from 12 to 14 days. Taste of cooked
samples of corn was not objectionable until the 23rd day of the
experiment. The appearance of the corn in plioseal in com-
parison with the control may be judged from Figure 24.
Loss in weight of the unhusked corn was not as great as
that of the husked corn but, as shown in Table 30, with unwrap-
ped it was approximately 10 to 20 times greater than with
wrapped. This was true for corn at both 370 F. and 70' F. for
all of the inspection periods. This is shown even more clearly
by the graphs of Figure 25.
Fig. 24.-Corn after 10 days at 37 F. (outside ears) pliosealed and
(center ears) not wrapped. Left two ears, Horsetooth, right two, Tux-
84 Florida Agricultural Experiment Station
The effect of various types of pliofilm wrappers on the
length of time that Golden Cross Bantam sweet corn remained
marketable has been tabulated and presented in Table 31. The
corn was judged marketable when it still had the garden fresh-
ness and flavor of fresh corn. This was determined by obser-
vation on the texture and appearance and by tests of the flavor.
A novel method of cooking the corn was discovered in the
process of testing some of the samples for taste. It was found
that the ears of corn in plioseal could be dropped into boiling
water and the entire cooking operation performed without break-
ing the sealed pliofilm wrapper. The normal cooking time was
not lengthened by this process. The taste was considered su-
perior by some, evidently because the sealed wrapper did not
allow the food
elements and vol- 20
atile esters which 2
affect flavors to CORN
be extracted from
the kernels by the
boiling water r. 15
ing feature of this
method of cook-
ing was that *
ears retained 0o
their warmth for
longer time when
left at room tem-
perature after .
did corn prepared
in the usual way.
The slight ther-
moplasticity o f
the air-tight pli-
ofilm wrap about 0 3 6 e 9 t 2 Ia 18 21
Time in Storage (ays)
the ear of corn
Fig. 25.-Percentage weight loss of corn at 37
allowed t h e F. and 70* F. during 21 days. Line 1 represents
wrapper to be ex- husked, 2 unhusked corn, and 5 pliosealed corn at
700 F.; 3 represents husked, 4 unhusked and 6
panded slight- pliosealed corn at 37* F.
Pliofilm in the Preservation of Florida Fruits and Vegetables 85
ly by the trapped air without appreciable pressure so that there
was no danger of its bursting. In some cases the pliofilm be-
came opaque during the boiling process.
Similar experiments were carried out using Tuxpan and Horse
Tooth varieties (Fig 23). These are hybrid varieties but are
more characteristic of field corn than sweet corn. Results were
similar to those obtained with Golden Cross Bantam. The
length of time that these varieties remained fresh and of good
quality was slightly longer than for the sweet corn. In all other
respects the data obtained closely resemble those presented for
Golden Cross Bantam.
TABLE 31.-EFFECT OF VARIOUS TYPES OF PLIOFILM WRAPPERS ON LENGTH OF
TIME (GOLDEN CROSS BANTAM) SWEET CORN REMAINED MARKETABLE AT COLD
STORAGE AND RETAIL STAND TEMPERATURES.
Length of Time the Corn in Various Wraps Remained
Temperature *Husked Husked **Unhusked Husked, Not
20-gauge Plioseal (Control) Wrapped
Sheet Wrap (Control)
37 F. 23 23 7 2
70 F. 10 10 3 1
*Husked-Corn from which the husk has been removed.
**Unhusked-Corn from which the husk has not been removed.
This method of preparation and type of wrapper may be of
advantage to the grower and shipper in that it would allow
them to maintain a high quality product. It also would eliminate
the necessity of paying freight on corn husks, but would necessi-
tate sanitary measures in the husking and wrapping process.
A transparent sealed package for corn should be welcomed
by the retail merchant. The more orderly display stands and
convenient marketing processes gained from existing transpar-
ent food packages have consistently earned a premium price.
Such packages sold under the brand name of the grower or re-
tailer would have the beneficial effect of standardizing quality
and making possible a more uniform product. They would also
eliminate the necessity for partially husking each ear for ex-
amination, which causes excessive drying of the corn.
Coreless carrots were wrapped in 20-gauge sheets of the
plioseal and placed in bags of 100-gauge pliofilm which were
86 Florida Agricultural Experiment Station
clipped at the top but not sealed. The plioseal was used on
carrots which had the tops cut off. One dozen bunches were
used for each condition, and were placed on shelves at 370 F.
and 70 F. All three types of wrapping were efficient in the
prevention of shriveling over a two-week period at 700 F. or
four weeks at 370 F. The tops were included with the carrots in
the 20-gauge wrap and 100-gauge bag and these remained green
and fresh for two weeks at 700 F. and four weeks at 370 F. Loss-
es in weight were negligible in all three types of package and
the carrots held their color perfectly.
Cauliflower of the Snowball variety was wrapped in 20-
gauge sheet wrappers and packaged in bags of 120-gauge plio-
film and held at 370 F. and 70' F. The bags were clipped at the
top but not sealed. Six heads were used for each condition and
these were packed in hampers. Results here were the same as
for cabbage. The garden freshness and original color of the
cauliflower were preserved for three weeks at 70' F. and five
weeks at 37 F. Loss in weight was 10 times greater in the
cauliflower not wrapped than in either the 20-gauge wrapper or
Brussels sprouts were packaged in pliofilm bags of 120-gauge
and placed at 37' F. and 70 F. Two dozen were placed in each
bag and three bags at each temperature. Results were the same
as for cabbage. The outstanding thing noted was the preserva-
tion of the green color (chlorophyll) in the Brussels sprouts.
Those protected by pliofilm changed only slightly in color
throughout the whole period. Those not wrapped lost the green
coloration and fresh garden appearance after a few days and
turned brownish. Those in the bag held in a state of garden
freshness for three weeks at 70 F. and six weeks at 370 F. Those
not bagged lost 15 times as much weight as those in the pliofilm
Italian Green Sprouting broccoli was tested in the same pro-
cedure as that of Brussels sprouts except that in addition to the
120-gauge pliofilm bag the broccoli was wrapped with 20-gauge
sheets. Six bunches were used for each condition and these
placed on shelves at both 370 and 700 F. Results with the
bag were almost identical with those of Brussels sprouts. When
Pliofilm in the Preservation of Florida Fruits and Vegetables 87
the 20-gauge wrapper was used on the bunched broccoli very
good results were obtained. The pliofilm was outstanding in
holding the broccoli in a state of garden freshness three to five
times longer than that not wrapped at both cold storage and
The average moisture content of the vegetables used in the
preceding experiments is 90 percent of the total weight. This
moisture is rather loosely held in the plant tissues, since most
vegetables possess too thin an epidermal covering to prevent
excessive moisture loss. The morphological structure of most
vegetables is such that it allows a large surface area for evap-
oration. Quality depends on crispness, and crispness on moisture
content. This is especially true for most leafy vegetables, such as
lettuce, cabbage and celery. Moisture loss in these vegetables is
the primary cause of wilting and loss of original color, texture,
flavor, and attractiveness. Other vegetables sold by weight have
their value decreased by moisture loss, even though the external
appearance is not as seriously affected.
The use of moisture-proof pliofilm as a wrapper on the
vegetables prevented dehydration but allowed normal respira-
tory gases to escape. In this manner the original quality and
appearance of these wrapped vegetables were maintained for a
longer period than would otherwise have been possible.
The low temperature at which vegetables are maintained
under refrigeration lowers the vapor pressure of the water con-
tained in the vegetables, so that the moisture loss is less rapid
than would be the case at room temperature. Refrigeration
also materially retards the growth of molds which cause decay,
and delays detrimental internal changes of a chemical nature
which affect the texture and flavor of the edible plant tissues.
The combination of the pliofilm wrapper with refrigeration
gave optimum results in maintaining the original quality of the
The preservation of harvest freshness and quality should
prove of benefit in the transportation of Florida produce to more
distant markets, and in permitting the grower and shipper to
place produce of higher quality on the markets. The use of at-
tractive transparent wrappers and packages not only draws at-
tention to the produce, but suggests that the grower has taken
considerable pride in growing and packing them, and so serves as
his guarantee of quality.
88 Florida Agricultural Experiment Station
The use of a wrapper or package that prevents wilting and
loss of quality should also prove of much benefit to the retail
merchant. This should remove much of the waste and extra
labor required for the trimming and handling of the vegetables
on the counter.
The consumer should welcome the use of a sanitary trans-
parent package and the identified brands which would aid in
the convenience of marketing. The maintenance of freshness
and quality is also of importance to the consumer after the pur-
chase has been made.
The effects of various types of pliofilm wrappers on the
preservation of several commercially important varieties of
Florida fruits and vegetables were studied under refrigeration
and conditions approximating those of the retail store. Taken
into consideration were effect on general appearance, taste, loss
in weight, length of time that fruits and vegetables can be held
in a marketable condition, and occurrence of physical deteriora-
tion and decay. The pliofilm wrapper also was subjected to
commercial shipping and storage tests in cooperation with sev-
eral Florida shippers.
Pliofilm was effective in reducing the weight loss of citrus
fruits without limiting the escape of the respiratory gases evolved
from the fruit. Three varieties of round oranges, three of Man-
darin oranges, four of grapefruit, two of limes, and one of kum-
quats, were wrapped in different types and gauges of pliofilm.
This fruit was compared with unwrapped fruit held under the
same conditions, and the data show that original weight, color,
texture and flavor of wrapped fruit were well maintained du-
ring the periods of observation. Loss of initial size and firm-
ness (shrinkage) was proportional to the percentage weight loss.
The original color of both the rind and stem button was
maintained in proportion to the preservation of other quality
factors. The preservation of the chlorophyll (green coloring
matter) of the stem button was an especially noteworthy feature
in the pliofilm-wrapped fruit.
Pitting, or localized drying of the rind, appeared on all types
of unwrapped citrus when held under refrigeration, but was
prevented almost entirely by the pliofilm wrapper. This was
found to be an important factor in the storage of limes and
grapefruit, permitting the storage life to be greatly extended.
Pliofilm in the Preservation of Florida Fruits and Vegetables 89
The original quality of round oranges was preserved best at
370 F., while Mandarin oranges, grapefruit, and limes showed to
best advantage at 420 F. Fruit held at either 37' F. or 420 F.
proved to be much superior in taste and appearance to fruit held
for the same length of time at 70 F. An advantage was ob-
tained at all temperatures from wrapping fruit in pliofilm. The
taste of the pliofilm-wrapped fruit at all temperatures proved
to be superior to that of the corresponding unwrapped or tissue-
wrapped controls. This difference was clearly distinguishable,
even after relatively short holding periods, and became more
accentuated with length of time in storage.
There was no significant difference in percentage of fruit lost
through decay in wrapped and unwrapped fruit until the latter
had so deteriorated through dehydration and pitting as to become
more subject to attack by molds. Refrigeration had a retarding
effect on the rate of decay. Nesting, and spread of mold spores
from sound to decayed fruit, was entirely eliminated by individ-
ual pliofilm wrappers.
Experiments conducted to test the advantages of the plio-
film wrapper in commercial storage operations gave results
comparable with those obtained in the laboratory experiments.
A method of preparing oranges for more convenient eating
out-of-hand was developed and subjected to a successful com-
OTHER FLORIDA FRUITS
Several types of pliofilm were used at refrigeration and re-
tail store temperatures to determine the effect of these wrappers
on the keeping quality of two varieties of persimmons, one of
mangos, five of peaches, and five of avocados. Unwrapped con-
trol fruit were placed under the same conditions in each case
and were used for a comparison of the effect of the wrapper
on the keeping quality of the fruit.
At all temperatures the softening of the persimmons was
retarded by the pliofilm wrappers. Wrapped fruit softened ap-
proximately one week later than those not wrapped. Also,
wrapped fruit at cold storage temperatures of 420 F. and 370 F.,
after reaching the edible soft-ripe stage, remained marketable
three weeks longer than that not wrapped and at the retail
stand temperatures of 70 F. one week longer in the edible soft-
ripe stage. The optimum temperature for holding persimmons
was found to be 42 F.
The optimum temperature for holding Haden mangos was
90 Florida Agricultural Experiment Station
370 F. The time required for softening to an edible stage under
all conditions of the experiment was twice as long for the fruit
wrapped in pliofilm as that not wrapped. The length of time the
fruit remained marketable in good edible quality at any one tem-
perature after softening was also doubled by the use of pliofilm
The pliofilm wrappers more than doubled the marketable
life of the five varieties of peaches at each of the temperatures
used. The initial freshness, color, texture and taste of the
wrapped peaches were well preserved by pliofilm wrapping du-
ring the entire storage time of four and five weeks. The best
temperature for storage of peaches was found, to be 420 F.
The flesh darkened after two weeks when the fruit was held at
a temperature of 37 F.
Better results were obtained with the late season varieties
of avocados, especially Lula and Taylor, when wrapped in plio-
film than with the early West Indian varieties. The best tem-
perature for holding avocados was found to be 42 F. At this
temperature the pliofilm-wrapped Lula or Taylor varieties re-
mained in a marketable condition from two to four weeks longer
than those not wrapped. The wrapped fruit remained in good,
firm condition six weeks in cold storage and from seven to 14
days after removal to room temperature (70 F. to 80 F.) com-
pared with three to four weeks for unwrapped fruit in cold
storage and four to eight days after removal to room tempera-
The effect of pliofilm wrappers was studied in preserving the
original quality of several important Florida vegetables during
short holding periods. Color, flavor, general appearance and per-
centage loss in weight were recorded and in most cases presented
in tabular form. In some cases vitamin C content was deter-
mined. These experiments were conducted under refrigera-
tion and at the average temperature of the retail stand.
Several types of pliofilm wrappers were used in the investi-
gations and the produce in these was compared with unwrap-
ped control samples to evaluate the effects of these wrappers on
The percentage weight loss of the unwrapped produce av-
eraged 20 times greater than that protected by pliofilm, and the
high percentage weight loss was accompanied by shriveling,
Pliofilm in the Preservation of Florida Fruits and Vegetables 91
change in color, and loss of flavor. The pliofilm wrappers were
very efficient in preserving the original harvest quality and ap-
pearance. The wrapped vegetables remained in this condition
and were marketable from two to 10 times as long as those
vegetables not so protected.
The plioseal greatly added to the appearance of individually
packaged vegetables and was equal to the sheet-type wrapper in
Appearance and tensile strength of the pliofilm wrapper
were unaffected by temperature, humidity, or other conditions
of the experiments.
Fabricated bags of 120-gauge material, closed by folding,
were effective in preserving freshness, and were quite durable
even when subjected to rough handling.
A larger amount of the original vitamin C content in the
vegetables tested was retained during storage in those samples
protected by pliofilm.
A new type package was developed for more efficient and
sanitary marketing of corn on the cob.
The authors express appreciation and thanks to all who have as-
sisted in any way in the conduct of this study; especially to the Goodyear
Tire and Rubber Co. for supplying laboratory assistance and materials;
to Mr. G. H. Blackmon for his assistance in photography; and to Mr.
Erle Wirt, Jr., for his assistance in carrying out many of the experiments.
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