Bulletin 681 September 1964
Better Handling of Florida's Fresh
University of Florida, Gainesville
I R Rc-kenbach. Director
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R R Pckenbach. Director
This bulletin has been written by the Fresh Fruit Handling
Section of the Citrus Experiment Station, University of Florida,
and the research staff of the Florida Citrus Commission at the
request of the Florida Fresh Citrus Shippers Association. Dr.
W. G. Long, formerly section leader, acted as editor. The au-
thors of the different sections are listed in the contents. Read-
ers may contact the Citrus Experiment Station for further in-
formation about better handling of citrus fruits.
This bulletin is dedicated to those who grow, pack, and mar-
ket better citrus fruit and lead the way for others who will follow.
Cover: An over-all view of a modern Florida packinghouse.
CONTENTS ..:': ;
SUMMARY ..... ------..... ..------------------ .... .. .......... 4
INTRODUCTION .--..-. --......... ....- - -------....-......-- ....- -- ---... ................ 5
FIELD HANDLING METHODS IN COMMON USE IN FLORIDA ................................ 5
F. W. Hayward and W. G. Long
DEGREENING AND NATURAL COLOR
Fruit Color: Its Changes and Significance ........--.................................... 7
M. F. Oberbacher
Ethylene Degreening ---..................... ......-----------....-... ........- 8
E. F. Hopkins and A. A. McCornack
CONVENTIONAL PACKINGHOUSE LINES AND EQUIPMENT IN FLORIDA .......... 12
W. G. Long
PRESIZING AND PREGRADING -----........--...... ....-----.....-............-----.... 13
W. G. Long
STEM-END RIND BREAKDOWN ........-- -............ -............. ..............-......... 15
E. F. Hopkins and A. A. McCornack
WASHING CITRUS FRUITS ---.......----............ ................... ..... 16
F. W. Hayward and W. G. Long
COLOR-ADDING ...-- ......-.. ...-....-------------- -....---- ............ ............. 20
F. W. Hayward
Solvent-Type W ax ---...........---......--........... ----........ ...............---.......... 23
E. F. Hopkins and A. A. McCornack
W after Emulsion W ax .-...... .....---............-.. ---.. ..... .................. 23
E. F. Hopkins and A. A. McCornack
DECAY CONTROL ........--------------....--... ...- --.... ... .... ............... ......---- 25
E. F. Hopkins and A. A. McCornack
GRADES AND GRADING ..---.-----..........- ..- -.................................. 28
W. G. Long
PACKAGES AND PACKING ........----......-............... ............. 30
W. G. Long
PRECOOLING AND STORAGE .... -........... .... ...... .......................... .... 32
F. W. Hayward and M. F. Oberbacher
How PACKING AFFECTS THE FRUIT .........-----..........-. ........-............ 35
H. M. Vines
SUGGESTED READING ...-....--......-..- ------ ---------....... .... ....... ......... 37
The Ten Requirements
1. Pick and handle fruit carefully to avoid injuries. Injuries
(plugging, punctures, cuts, or abrasions) increase green
mold and loss by decay.
2. Degreen under proper conditions if degreening is necessary.
Stem-end rot is increased under degreening room conditions,
and stem-end rind breakdown results if the relative humid-
ity is too low.
3. Wash properly to remove dirt and residues. It improves
4. Apply color-add as recommended if color-add is necessary.
It improves appearance if it's a good crop of fruit.
5. Apply fungicides to reduce decay. Save part of the fruit
that is usually lost to decay, and make more customers
6. Wax properly to preserve quality and improve appearance.
Waxing reduces shrinkage and stem-end rind breakdown,
and gives fruit a shine to attract consumers.
7. Handle promptly and properly to avoid stem-end rind break-
down. Low humidity in the grove or packinghouse can dam-
age much fruit.
8. Grade and size properly. It results in a more attractive and
9. Precool and refrigerate promptly to reduce decay and pre-
serve quality. It means money in your pockets.
10. Increase efficiency of operations to reduce costs. Presizing,
pregrading, proper handling, and suitable containers can
reduce costs, increase efficiency. Efficiency, costs, and profits
REMEMBER THESE TEN REQUIREMENTS FOR
GOOD CITRUS FRUIT HANDLING!
The quantity of fresh citrus fruit shipped annually is nearly
equivalent to the total amount of all deciduous fruits shipped.
In some respects the shipment of citrus-is the more difficult, be-
cause the citrus production areas are usually more distant from
the market centers. Florida, California, and Texas produce most
of the citrus, but deciduous fruits are produced throughout the
United States. The long trip involved in marketing citrus fruits
requires careful handling in the packinghouse to insure good con-
dition on arrival.
In an average season, appreciable quantities of the citrus
fruit shipped to market are lost through decay. Rough handling,
improper degreening, and other practices increase the amount
of decay. Through proper handling and packing, this loss can
be reduced and the appearance of the fruit improved so that it
appeals more strongly to buyers and consumers. Fruit sales,
like grocery sales, must be on a repeat basis if they are to be
The purpose of this bulletin is to point out and explain the
best handling and packing methods in the hope that a better
product may be marketed. The end result will be continued de-
mand, which is so vital to the economy of the citrus industry.
This will mean more profit to growers, packers, and shippers,
and better quality citrus fruits for the consumer.
FIELD HANDLING METHODS IN COMMON USE
Harvesting.-Citrus fruits are harvested either by pulling
or by clipping from the tree. The rind of tangerines is often
damaged around the stem end if they are pulled, so tangerines
are usually clipped. Clipper cuts and long stems that puncture
other fruits should be avoided because they cause increased green
mold decay. Pulling usually decreases the amount of stem-end
rot, since the flower calyx (button) is removed. Pulling re-
quires less labor, and it is faster. Fruit that is pulled, however,
is more subject to green mold decay.
The pulled or clipped fruits are placed in a canvas picking
bag which the picker carriers over his shoulder. The bag should
be carried carefully to avoid bruising the fruit against the lad-
der. The bottom of the bag opens, so that the fruit can be
emptied into field boxes, pallet boxes, carts, baskets, or loaders.
6 Florida Agricultural Experiment Stations
The bag should be lowered to the bottom of the container, so
that the fruit does not drop and bruise as the bag is raised to
empty it. Pickers should wear gloves to reduce cuts and injuries
to the rind.
Handling in Field Boxes.-The standard field boxes are usu-
ally made of cypress, but other woods may be used. Size is speci-
fied by the Florida Citrus Code of 1949, as amended-601.86:
All field boxes used in the purchase, sale or handling of citrus
fruit from or for the grower by a citrus fruit dealer in the
state shall be of the uniform standard size of thirty-one and
one-half inches long, thirteen inches high, and twelve inches
wide, inside measurements, and shall be divided into two com-
partments by a center partition of at least three-fourths-inch
thickness; and each of these compartments thus created shall
have a cubical capacity of not to exceed twenty-four hundred
An empty box weighs about 17 pounds. When full, it will weigh
from 100 to 120 pounds, depending upon fruit size, variety, and
quality. Field boxes were designed to hold enough fruit to pack
out a full 13/-,-bushel box. However, they will not pack out to
a 1:%-bushel box if the quality is low or if the field box is not full.
The desire for a high "pack out" frequently results in filling field
boxes too full. Crushed or cut fruit is often the result. Sales
by weight discourage this practice.
Handling in Pallet Boxes.-Bulk boxes or bulk bins are usu-
ally about 48 inches square and 32 inches deep (outside). They
are usually made of wood, but some are reinforced with sheet
metal or angle iron. The usual capacity is 10 to 12 boxes (or
approximately 1,000 pounds) of oranges. Pallet boxes weigh
from 130 to 258 pounds, depending upon the materials used in
Fruit is placed in the pallet boxes by the picker. A tractor
with a forklift loads the pallet boxes on flatbed trucks or semi-
trailers. They are removed at the packinghouse with a forklift
and placed in degreening rooms or emptied directly onto the
packinghouse line. Pallet boxes are ideal for holding fruit dur-
ing degreening or after processing.
The cost of pallet box handling is lower than field box han-
dling. Injury to the fruit is about the same, and degreening
seems to be no problem. Less labor is required, and operations
may be more efficient.
Bulk Handling.-Fruit is picked into 20-box carts, 10-box
expanded metal baskets, or bulk trucks and then transferred
Better Handling of Florida's Fresh Citrus Fruit 7
with highlift trucks or vertical lift elevators to semitrailers.
By use of baffles and padded floors, injury to the fruit is greatly
reduced. The semitrailers are run onto a tilted ramp, and the
fruit is unloaded through the side or tailgate onto a conveyer
belt. Fruit can be presized and pregraded before passing into
the bulk coloring bins for degreening or storage. Fruit is re-
leased from the bottom of the bins onto a conveyer belt which
connects with the packing lines.
Bulk handling saves 6 to 11 cents per box in handling costs
over field box methods, largely because of greater efficiency and
reduced labor. This method permits presizing and pregrading
before degreening, which increases the capacity of the packing-
house early in the season. The main disadvantage appears to
be the cost of the change-over from a field box to a bulk handling
Combinations of bulk field handling and pallet box packing-
house handling have been used. Degreening in pallet boxes uses
space more efficiently and requires less overhead than bulk de-
greening rooms. When degreening is not required, bulk handling
is employed throughout the whole operation. This points out
the very important fact that a packing system should be de-
signed to fit the conditions-present and future.
DEGREENING AND NATURAL COLOR
Fruit Color: Its Changes and Significance.-In the fall, citrus
fruits begin to change color. Spots on the side toward the light
begin to lose their green chlorophyll pigments, unmasking the
yellow pigments that have been there all along. At this time
the yellow pigments begin to increase in amount. The spots
increase in size and number and unite until the entire surface
of the fruit is yellow.
The change in color is associated with cool nights (particu-
larly below 50- F). The temperature required to stimulate loss
of green color of fruit on the tree is lower for oranges than for
grapefruit. Fruits of some varieties, such as grapefruit and
Hamlin and Parson Brown oranges, mature internally but do
not develop a satisfactory color until cool weather, which usually
occurs in early December. Since the natural development of
fruit color usually occurs after the beginning of the harvesting
season, fruit must be treated to remove the green color (de-
greened), allowing the natural orange or yellow color to pre-
8 Florida Agricultural Experiment Stations
If green fruits are picked and placed in storage at 50', 60,
of 700 F, they will lose their green color in 1 to 4 weeks, depend-
ing upon maturity and the storage temperature. A temperature
of 60 F is superior to 500 or 700 for degreening in storage or
The length of time required to degree a fruit depends upon
the degree of natural color break and maturity. The lighter
the green color and the more mature the fruit is, the less time
is required to diminish the chlorophyll to a tolerable level. Ac-
tually, most fruits, if not all, never lose all their chlorophyll.
Very sensitive color measuring instruments show some chloro-
phyll still present long after the eye can no longer see it.
In the late varieties of oranges and in grapefruit, some chlor-
ophyll is produced in the rind when vigorous vegetative growth
resumes in the spring. This phenomenon is called "regreening."
Florida Valencia oranges, Pope Summer oranges, and grapefruit
usually regreen. Inside fruits which are shaded by the leaves
never entirely lose their green color; this should not be con-
fused with regreening. These fruit actually become a little
greener when regreening occurs.
Research results show that within any given load of fruit,
a strong relationship exists between color and many other de-
sirable qualities, such as taste and Brix. Color was measured
by both reflected and transmitted light; in most determinations,
a stronger correlation was found when reflected light was used.
These results point out a possibility of color sorting for quality
in addition to sorting into different color lots for efficient de-
greening. Color sorting for degreening has been practiced on
the pregrading conveyer of one or two houses for many years.
It is a sensible and efficient practice with some crops of fruit.
Ethylene Degreening.-The consumer expects citrus to have
a color characteristic of the specific variety. For this reason,
poorly colored mature fruit is treated with ethylene gas in rooms
referred to as degreening or coloring rooms. (The term "de-
greening" is preferred.)
The loss of citrus fruit due to mold decay is less during the
degreening part of the season. Some healing action of the fruit
closes superficial injuries under conditions found in degreening
rooms. This prevents entrance of mold spores. Holding fruit
at degreening room temperature and humidity but without eth-
ylene is called curing. The growth of stem-end rot organisms
is speeded up in the degreening room. Usually, degreened
"fruit will have less mold decay but more stem-end rot. The
Better Handling of Florida's Fresh Citrus Fruit 9
longer fruit remains in the degreening rooms, the greater the
total decay loss.
Degreening rooms should be tight enough so that the proper
concentration of ethylene gas, 1 part in 50,000 parts of air, can
be maintained. Ethylene gas is purchased in gas storage cyl-
inders and piped into the degreening rooms through gas-tight
Ethylene is introduced into the room by the commonly used
"trickle unit" illustrated in Figure 1. To reach the initial con-
centration rapidly, the water column is raised to 3 inches on the
scale and left there 1 minute for each 100-box capacity of the
room. After the required concentration is reached, the rate is
adjusted to 10 bubbles per minute per 100-box capacity of the
room for the remainder of the degreening period.
Forced circulation of air in degreening rooms must be suffi-
cient to provide perceptible movement in all portions of the
room. Proper air circulation requires adequate fan capacity.
This varies between 625 and 1,500 cubic feet per minute per
1,000 cubic feet air volume of the room. Ventilation ducts should
be provided so that a regulated amount of fresh air is added con-
tinuously to keep the concentration of carbon dioxide below 1
percent. If carbon dioxide gas is allowed to build up, degreen-
ing slows and stops. Adjustable fresh air vents should be placed
in all gas-tight degreening rooms so that a constant supply of
fresh air is introduced when the room is in operation. Proper
adjustment of fresh air vents makes it unnecessary to air de-
greening rooms. Gas-tight degreening rooms without fresh air
vents must be aired several times daily. Canvas degreening
rooms usually have enough natural exchange of fresh air so
that air vents are not necessary.
Early in the season, citrus fruit may be degreened for as
long as 72 hours. Longer degreening is not a desirable commer-
cial practice. Fruit should be held in the degreening room for
only the minimum time necessary to get the desired color.
Twelve hours is the shortest practical degreening time for more
fully colored fruit.
Degreening rooms cannot be operated above 850 F dry bulb
reading with applied heat (Florida Citrus Commission Regula-
tion 13). The wet bulb reading should be 820 to 83 F, which
gives 88 to 92 percent relative humidity. Humidity is usually
controlled manually. When the temperature is below 85 F,
moist steam can be used to increase humidity. When the tem-
10 Florida Agricultural Experiment Stations
Fig. 1.-"Trickle unit" used for dispensing ethylene gas to a degreen-
ing room. Water or white oil is introduced through the funnel "F" until
the level is as shown. Ethylene from the main supply line enters through
the cut-off valve "C" and is regulated by the needle valve "R." The de-
livery pipe "A" is inverted so that the ethylene has to bubble through the
water. The metering orifice "M" causes a back pressure, resulting in a
rise in the manometer column proportional to the rate of gas flow.
(Courtesy Food Machinery and Chemical Corporation.)
Better Handling of Florida's Fresh Citrus Fruit 11
perature is higher, water mist should be used to increase hu-
midity. Place water mist nozzles so the mist is carried through-
out the room by the fan.
Excess ethylene may injure the rind of citrus fruits. Tan-
gerines and Temple oranges are especially sensitive to ethylene
burn. This injury is not usually noticeable until several days
following ethylene treatment (Figure 2). Ethylene injury is
usually increased by handling, particularly brushing. Gassing of
Temple oranges should be avoided. Only tangerines that have
a good natural color break should be picked and gassed.
Fig. 2.-Blemished fruit was gassed 68 hours at a low average relative
humidity (68 percent). Unblemished fruit was from same lot but not
gassed. Injury became evident 5 days after picking.
12 Florida Agricultural Experiment Stations
For more details on citrus degreening, refer to the Univer-
sity of Florida Agricultural Experiment Stations Bulletin 620,
"Degreening of Florida Citrus Fruits," by W. Grierson and
W. F. Newhall.
CONVENTIONAL PACKINGHOUSE LINES
AND EQUIPMENT IN FLORIDA
A packinghouse line should be designed so that the largest
amount of fruit packed is not greater than 90 percent of its ca-
pacity. Also, a greater number of operating days and more con-
tinuous utilization of the packinghouse line lead to greater effi-
ciency and a lower packing cost per box. The choice of handling
systems, i.e., bulk, pallet box, field box, or combination, depends
upon the size of the groves to be harvested and their location in
relation to the packinghouse.
Presizing and pregrading to remove cannery fruit are de-
sirable before the fruit enters the degreening bins or rooms, or
the packing line.
The packing line begins with the dumping operation, i.e.,
dump belt, dumping machines, or the belt from the bulk rooms
or bulk unloading ramp. Sometimes the fruit is conveyed to a
soak tank, where it is immersed in water or a cleaning solution
for a few minutes. In most cases soak tanks are not necessary
for good cleaning, so they are no longer recommended, although
many older houses still have them. A fruit cleaner is applied
as a foam as the fruit enters a transverse brush washer. The
loosened dirt is rinsed off with a cold water spray. Fruit passes
over a water eliminator and enters the color-add tank or by-
passes it. The color-add tank also may be used for Dow-Hex
treatment (but not in combination with color-add). The fruit
enters either the water waxer followed by the drier, or the drier
and then the solvent waxer. Fruit is dried and brushed (drier-
polisher) ahead of the solvent waxer, because such pretreatment
is essential for maximum gloss of the wax coating.
The "color-added" stamping machine is usually placed after
the waxer and drier. The fruit ready for packing passes over
a grading belt and is hand-sorted into the desired grades. The
fruit is sized with a central (master) belt, chain, or a bin-type
sizer and packed from roll-board stations, bins, bagging ma-
chines, count-pack, or similar machines. Since most houses pack
in many containers, i.e., half and full wirebound boxes, includ-
ing half straps, cartons, "Duralugs," fiber mesh bags, and poly-
Better Handling of Florida's Fresh Citrus Fruit 13
ethylene (poly) bags, and other consumer-size containers, the
traffic distribution to and from packing stations is a complex
problem. While it would probably be difficult, it would greatly
simplify packinghouse operations to standardize on two or three
containers. Packing, closing, distribution, transporting, and
marketing would also be a much simpler task.
The packed containers are handled by conveyer, pallets, fork-
lifts, or hand trucks. The method that is used depends upon
the scale of operations.
For large scale operations it is advantageous to have two
lines, a large one for oranges and grapefruit, and a smaller one
designed specially for tangerines, tangelos, Temples, and other
tender varieties. In periods of heavy harvest, the second line
may be used for the overflow of oranges and grapefruit.
Precooling and refrigeration are very desirable for citrus.
Decay control, shrinkage control, and quality are maintained for
a longer time. Suitable refrigeration services (ice, fans, vents)
should be provided in transit. Probably one of the greatest ad-
vances in transportation has been the "piggy back," in which
specially constructed semitrailer trucks are loaded on railroad
flatcars for long distance shipping. Its great virtue is reliable
refrigeration, but stacking patterns and direction of loading are
very important. Hydrocooling and poly bags are not nearly as
effective in maintaining freshness and quality unless continued
refrigeration is provided. Since citrus does not need ripening
after harvest, refrigeration should be provided from the time
it is packed until the last fruit is used from the consumer's re-
PRESIZING AND PREGRADING
Presizing removes the small and large fruits that are not
saleable as fresh fruit, or enables selection of certain sizes for
the orders on hand (Fig. 3). The advantages of presizing are
that sized-out fruit brings a higher field-run price than packing-
house eliminations (however, they are often mixed together),
and the effective size of the packinghouse is increased.
Pregrading results in economy and greater efficiency of op-
eration (Fig. 4). The sound fruit that is graded out because
of superficial defects also brings higher field-run prices. The
culls (splits, rots, and cracked fruits) are removed, thus elim-
inating an important source of infection and saving many other
fruits from being lost through green mold rot.
14 Florida Agricultural Experiment Stations
Fig. 3.-The presizer often follows the pregrader (Fig. 4), but this should
be reversed. Note the soak tank and washer in the left background.
Fig. 4.-The pregrading set-up is often a simple one, but it
improves the operations in many ways.
Better Handling of Florida's Fresh Citrus Fruit 15
The use of presizing and pregrading is an efficient practice.
Most packinghouses grade and size-out at least 25 percent of
their fruit. If this is done by presizing and pregrading, the effec-
tive capacity of the house is increased 25 percent. In addition,
water, electricity, soap, color-add, and wax are conserved, and
degreening or storage space is better utilized.
STEM-END RIND BREAKDOWN
There are many causes of rind pitting and breakdown in
citrus fruits. One type called stem-end rind breakdown (Fig. 5)
is frequently found on oranges in the market place, but is rarely
observed in the packinghouse. It begins to develop 5 to 7 days
after picking and is primarily due to drying out of the fruit
(Fig. 5). The symptoms are shriveled and pitted areas, usually
^ .. .- s
Fig. 5.-Stem-end rind breakdown of Pineapple oranges.
16 Florida Agricultural Experiment Stations
on the stem end of the orange, which give the fruit an over-
mature look and result in increased spoilage. Stem-end rind
breakdown is also known by other names such as brown-stem,
stem-end pitting, and stem-end aging. The Pineapple orange
is the most susceptible commercial variety grown in Florida, but
all the orange varieties show this pitting to some degree, de-
pending on the season and how the fruit is handled. Fruit from
different groves and different pickings from the same grove
may vary in susceptibility. Grapefruit varieties and tangerines
have not been known to develop this type of defect.
Stem-end rind breakdown may develop when oranges are: (1)
degreened at lower than recommended humidity; (2) allowed to
remain on the packinghouse floor for a day or more before pack-
ing, particularly when the humidity is low; or (3) subjected to
any delay in handling between picking and waxing.
To prevent the development of stem-end rind breakdown,
oranges should be packed as soon after picking as possible. Dur-
ing degreening, the relative humidity of the coloring room should
be kept at 85 percent or above. This humidity is obtained with
a spread of 2 or 3 degrees between the wet and dry bulb ther-
mometers. When there is a delay between picking and packing,
and the fruit does not need degreening, it should be placed in
a degreening room and the relative humidity kept at 85 percent
or above with fans operating. No ethylene or heat should be
A good wax film must be applied to the fruit following proc-
essing. If too little wax is applied or if it is applied unevenly,
particularly to the stem end of the fruit, stem-end rind break-
down may develop. This results in down-grading or refusal of
the shipment, or an increase in the amount of spoiled fruit at
WASHING CITRUS FRUIT
Citrus fruits are usually washed in brush washers using a
cleaner of some type, followed by a clear water rinse to remove
the loosened dirt, oil, residues, scale deposits, etc. In older pack-
inghouses, a soak tank was sometimes placed before the washer
to soften dirt, resides, etc., before washing (Fig. 6). The soak
tank may contain water, or a water conditioner or soap (de-
tergent) may be added to help wet the fruit and "cut" the oil
and scale deposits. Soak tanks can cause water injury if the
tank design permits fruit to accumulate in corners and remain
stationary for long periods of time, or if the line is shut down
Better Handling of Florida's Fresh Citrus Fruit 17
and fruit is left standing in water or solution. Soak tanks are
not usually recommended because of possible water injury and
because they are unnecessary for good cleaning, unless the fruit
is very dirty or oily.
Fig. 6.-Soak tank in center foreground and fruit washer with rinse-
off and water eliminator. In the background are shown the "bypass" belt
on left, color-add tank on right, and two types of driers in distance.
Citrus cleaners usually consist of a soap plus a water condi-
tioner such as soda ash or trisodium phosphate. A water con-
ditioner is needed if the water is hard. Detergents usually do
not need an additional water conditioner. However, detergents
do not break down in septic tanks as soap does, and after a period
of years they may cause malfunction of the tank. Most com-
mercial citrus cleaners contain a soap or detergent, water con-
ditioners, and additives that help do a better job of washing.
Dowicide A-hexamine solution may replace the cleaner (see de-
cay control section).
The only washer in use today is the transverse brush washer.
The brushes may be Tampico or palmetto fiber, but in recent
years synthetic fibers such as nylon, saran, polystyrene, poly-
propylene, vinyl chloride acetate, tynex, and other polymers have
come into common use. The fibers should be of proper size and
softness to remove dirt but not stiff enough to injure fruit.
Brush speed should not exceed 200 rpm. The recommended rate
18 Florida Agricultural Experiment Stations
of climb for the washer is inch per foot. In order to prevent
fruit injury, brushes should be inspected and replaced promptly
The cleaner is usually foamed onto the fruit from a shallow
pan by means of compressed air, or sprayed over the fruit with
the aid of a centrifugal pump (Fig. 7). After scrubbing on the
brushes, the fruit is rinsed under a spray of clear water (Fig. 8).
The excess water is removed by brass or sponge rubber elimina-
tor rollers or a slat or roller elevator before the fruit enters
the drier (Fig. 9).
Driers are usually one of two types: (1) slat or roller con-
veyers over which heated air from a bank of steam pipes or
radiators is blown by a series of fans (Fig. 10), or (2) trans-
verse brush driers which contain 40 to 60 horsehair or soft syn-
thetic bristle brushes instead of rollers or slats. Prolonged
brushing, high speed brushing, stiff bristles, and high tempera-
tures while drying should be avoided, because the amount of
rind injury (oleocellosis and stem-end rind breakdown) and de-
cay is increased, while shine may be decreased. Drier brushes
may remove scale insects not removed by the washer brushes.
The drier brush speeds should, not be over 150 rpm, and the
lowest amount of heat necessary to dry the fruit should be used.
Fig. 7.-The sudser-type washer with rinse-off and water eliminator.
Better Handling of Florida's Fresh Citrus Fruit 19
Fig. 8.-The "rinse-off.", Note that the fruit are well sudsed
before being rinsed.
Fig. 9.-The water eliminator removes excess water from the fruit
before it enters the drier, color-add tank, or bypass belt. Note "foam"
rollers on the bed of the eliminator.
20 Florida Agricultural Experiment Stations
Polishers containing brushes are sometimes used before sol-
vent wax is applied. The brushes should be soft and operated
at a speed of 150 rpm or less. Water waxes are applied ahead of
the drier, and polishers do not improve the shine, since most of
them are self-polishing. Slat or roller conveyer driers are often
Fig. 10.-Fruit entering the drier from the color-add tank.
Early oranges in Florida mature before nighttime tempera-
tures are low enough for the peel to develop a good orange color.
Late oranges tend to regreen during the spring flush of growth.
Degreening with ethylene removes the green color due to cloro-
phyll but leaves the peel a yellow or very pale orange. Since
many customers believe that oranges should be orange in color,
the process of color-adding with a dye was developed to improve
the eye-appeal and marketability of oranges.
The color-add process is subject to strict regulation under
the Florida Citrus Code of 1949, as amended, and Food and
Drug Administration to insure that the consumer receives whole-
some, mature fruit with good keeping qualities. Color-adding
is permitted for oranges, Temple oranges, and tangelos, but is
prohibited for grapefruit and tangerines. Maturity standards
for fruit to be color-added are higher for juice content, total
Better Handling of Florida's Fresh Citrus Fruit 21
solids, and Brix/acid ratio than the minimum required for nat-
ural-color fruit. Samples of coloring materials and details of
formulation and process must be submitted to the Florida De-
partment of Agriculture for analysis and approval prior to sale
to insure that materials which are harmless to fruit and con-
sumers will be used. The color characteristic of good natural-
color fruit may not be exceeded, and each fruit must be stamped
with the words "Color-Added" (50% Tolerance, 3/32-inch type).
Packages must also be labeled. Time and temperature of treat-
ment are limited by law (Regulation 12, F.C.C.) to protect keep-
ing quality of the fruit.
Only one dye is currently approved by the U. S. Food and
Drug Administration for coloring citrus fruit. This is 1-(2,5 di-
methoxyphenylazo)-2 naphthol, which is more commonly known
as Citrus Red No. 2. An official tolerance of 2 ppm has been
established based on the weight of the whole fruit. Residues
are easily determined by the method devised by Ting for Red
No. 32, the dye formerly used. This method consists of wash-
ing the dye from the fruit with chloroform and calculating the
concentration by comparing light absorption at 520 m1 with
that of a standard dye solution.
Numerous patents have been issued for processes and formu-
lations for coloring citrus fruits, but those currently used com-
mercially are all basically similar. The oil-soluble dye, Citrus
Red No. 2, is dissolved in an organic solvent, and this solution
is emulsified in water for use in coloring fruit. Solvents and
emulsifiers vary from one process to another, but in all methods
the fruit is treated with a dye emulsion, and the color is de-
posited in the oil cells of the peel. Stability of the emulsion is
critical in the color-add process. If too much emulsifier is used,
the dye remains in the emulsion and the fruit is not well colored.
Too little emulsifier results in breaking of the emulsion, which
leads to uneven color and injury to the peel of the fruit. For this
reason, field residues and broken fruit should not reach the
color-add tank, since they may react with the emulsifier and
cause the emulsion to break.
Equipment used to apply color-add emulsion to fruit follows
the washer in the packinghouse line and is quite standardized
in design (Fig. 11).) The color-add emulsion is contained in a
tank equipped with a thermostatically controlled steam coil to
maintain the desired temperature. The fruit travels above this
tank on a roller conveyer which rotates the oranges to assure
even coverage by the color-add emulsion. A centrifugal pump
22 Florida Agricultural Experiment Stations
raises the emulsion to a flood pan above the conveyer, and nu-
merous holes in this pan distribute a continuous flow of color-
add emulsion over the fruit passing beneath. Excess emulsion
passes through the conveyer back into the tank. Temperature
of treatment is controlled by the thermostat connected to the
steam valve, and duration of treatment depends on the speed of
the conveyer. Maximum legal limits for treatments are 4 min-
utes at 120 F for oranges and 21,, minutes at 115" F for Temple
oranges and tangelos. After the fruit leaves the color-add
tank, it is rinsed with a water spray to remove excess emulsion
and cool the fruit.
Color concentrate should be kept tightly covered and stored
without being exposed to extreme temperatures. Manufacturer's
directions for making up the color-add bath and maintaining con-
centration should be carefully followed. A proportioning pump
coordinated with the dump rate is a good way to correct for de-
pletion of color in the bath. Flood pans and screens should be
cleaned at least daily. Fruit should be well washed and excess
water eliminated before reaching the color-add applicator, and
decayed or broken fruit should be removed. Green fruit cannot
be dyed to give a satisfactory orange color.
Fig. 11.-Fruit leaving the washer and entering the "color-add" tank,
where a dye solution is applied to the fruit. Note the "bypass" belt on the
left for natural color fruit.
Better Handling of Florida's Fresh Citrus Fruit 23
Citrus fruit are waxed to replace the natural wax removed
in washing, to reduce shrinkage and weight loss, and to increase
consumer appeal by making the fruit shine. A good wax deposit
may provide shrinkage control between 40 and 50 percent of the
weight lost by unwaxed fruit of the same lot. The natural wax
on citrus fruit gives about 20 percent shrinkage control com-
pared to washed, unwaxed fruit. Greater than 40 to 50 percent
shrinkage control can be obtained, but the heavier wax deposit
required interferes with the normal respiration of the fruit, and
off-flavors may develop. Drying time is also greatly increased
for heavier wax deposits.
Two types of waxes are available for use on citrus fruits.
Solvent-Type Wax.-The most common wax of this type con-
sists of a coumarone-indene resin dissolved in a volatile petroleum
ether solvent. The Food and Drug Administration has estab-
lished a tolerance of 200 ppm for this resin. Fruit to which sol-
vent-type waxes are to be applied is washed, dried, and usually
polished, using soft brushes (such as horsehair) before the wax
is applied. The wax is atomized on the dry fruit as it rolls on
metal rollers (Fig. 12). Then the waxed fruit is dried on a slat
conveyer. This is usually built in two sections so that the fruit
makes a half turn as it rolls onto the second section. This ex-
poses all sides of the fruit so that the solvent evaporates quickly,
leaving the wax.
The unwaxed fruit passing through the first part of the drier
should be on a slat or roller conveyer. Instead, many packing-
houses use brushes in both the dryer and polisher. To avoid in-
jury to tender-skinned fruit, brushing should be held to a mini-
mum. The polisher part of the drier usually contains horsehair
or other kinds of soft brushes. Some packinghouses have re-
placed the brushes in the drying operation with a slat conveyer
before the solvent-type wax application with satisfactory results.
Polisher brush speed should be 200 rpm or less to avoid injuring
the peel of the fruit. On separate packing lines for tangerines
and other soft citrus fruit, 150 rpm is a better brush speed.
Excess drying is harmful, but the fruit must be free of moisture
when the solvent-type wax is applied to insure a good shine.
Solvent waxes containing fungicides for decay control are avail-
Water Emulsion Wax.-Waxes of this type are applied to
fruit without previous drying. The fruit is washed in the usual
24 Florida Agricultural Experiment Stations
manner, and excess water removed on a roller bed or by water
eliminators. The wax is applied either by fixed nozzles or a trav-
eling nozzle. Using either method, the wax is applied as a mist.
The fruit is carried under the wax applicator on soft brushes
or some type of roller that helps to distribute the wax evenly
over the surface of the fruit. Water emulsion waxes can also
be applied as a bath in a small tank, but this method is not
usually recommended because of the heavy deposit that results.
Fig. 12.-A solvent-type wax applicator. Note flue which
removes flammable fumes.
The waxed fruit is dried with applied heat on a slat or a
roller conveyer. The roller conveyer is installed so the rollers
do not revolve except at designated places. The fruit makes at
least a half turn during the drying operation, so that all sides
are exposed to the heat. Waxes of this type can be used on any
citrus fruit but are especially recommended for tender fruit that
may be injured by unnecessary brushing. Fungicides are often
incorporated in water emulsion waxes.
A good wax, properly applied, reduces moisture loss from the
fruit, resulting in a naturally firm-appearing fruit during the
marketing and consumption period.
Better Handling of Florida's Fresh Citrus Fruit 25
Loss from decay is an important economic factor in the mar-
keting of fresh Florida citrus fruits. The average decay loss
for a 7-year period at the Citrus Experiment Station was 19
percent 2 weeks after picking. This average included four va-
rieties of oranges gassed and ungassed but not treated for the
control of decay and held at 700 F.
Four species of fungi cause nearly all the decay that occurs
during the marketing period. Stem-end rot is caused by either
Diplodia natalensis or Phomopsis citri (Fig. 13). The most prev-
alent mold is green mold, Penicillium digitatum, but blue mold,
Penicillium italicum, is sometimes found on Florida citrus fruit
Fig. 13.-Stem-end rot on oranges showing typical symptoms.
The fungi that cause stem-end rot are already in the calyx
lobes of the fruit button at picking time. The loss from these
two fungi usually does not show up until the second week follow-
ing picking. Stem-end rot losses are usually heavier during the
26 Florida Agricultural Experiment Stations
degreening period and the warm spring and early summer weath-
er. The types of decay caused by these two fungi are so similar
in appearance that they are commercially considered as one
form of decay.
Fig. 14.-Green and blue mold rot on oranges.
The molds differ in that they usually enter the fruit only
through injuries that occur during the picking, packing, and mar-
keting period and may be evident at any time. Mold losses are
usually more severe during January and February.
Fungicides.-Most Florida citrus can benefit by the use of
fungicides during packing. Those that are effective for Florida
citrus and have been approved by the Federal Food and Drug
1. Diphenyl (also called biphenyl)-residue tolerance 110
2. Sodium o-phenylphenate (Dowicide A)-residue tolerance
10 ppm calculated as o-phenylphenol.
Diphenyl.-Pads impregnated with diphenyl are placed at the
top and bottom of %s-bushel fiberboard cartons. Two pads con-
tain approximately 4.7 grams of diphenyl. In wooden containers,
diphenyl-treated liners that completely enclose the fruit can be
used. The odor is objectionable, but it is lost when the fruit is
exposed to air for several days.
Diphenyl should be used with polyethylene bags of citrus in
master containers. The pads are placed in the bottom and top
Better Handling of Florida's Fresh Citrus Fruit 27
of the master container, not in the bags. The decay-inhibiting
effect of the diphenyl usually lasts for at least a week after the
pads are removed.
For good decay control, the diphenyl pads or liners must be
fresh. Keep them sealed in glassine paper or foil when not in
use. When it is necessary to keep diphenyl pads for an extended
period, they should be kept in a sealed package under refrigera-
Sodium o-phenylphenate.-The trade name of this material
is Dowicide A. The solution is made safe to use on fruit by add-
ing examine (hexamethylenetetramine) before treating citrus
fruit. Caustic soda (NaOH) is added to keep the solution highly
alkaline (11.5-12.2 pH). Dowicide A-hexamine can be used in
the packing line in one of three ways:
1. Dip treatment.
2. Flooded on in a color-add applicator.
3. Flooded on washer brushes sufficient to wet the fruit
thoroughly (used in place of soap).
The treating solution is made using 2.0 percent Dowicide
A, 1.0 percent examine, and 0.2 percent caustic soda in water.
The temperature of the Dowicide A-hexamine solution should
be about 900 F while treating fruit. The temperature should
never go above 950 F. All fruit must be rinsed with clear water
after the treatment. A Brix hydrometer, standardized at 200
C, is used to measure the strength of the solution. A solution
of the right concentration for treating fruit will have a Brix
reading of 2.7.
The recommended period of immersion is 2 minutes when
treating by the dip method. The length of treatment is 3 to 4
minutes when the fruit is flooded in a color-add tank. The length
of treatment when fruit is flooded on the washer brushes is set
by the construction of the washer, but it should not be less than
2 minutes. Fruit may be burned if left in contact with Dowicide
A-hexamine solution for more than 5 minutes.
Dowicooling.-Good decay control has been obtained using
0.1 percent Dowicide A at pH 10.5 in the water of a hydrocooler.
Cleaning Equipment.-Dowicide A-hexamine treating equip-
ment can be cleaned at the end of the packing season using a 5
percent caustic soda solution (NaOH) at a temperature of 100'
to 120' F. Circulate this solution through the pipes, flood pans,
28 Florida Agricultural Experiment Stations
etc., for 10 to 15 minutes. Use it to scrub surfaces.coated with
Dowicide A-hexamine deposits. Rinse all surfaces where caustic
soda was used at least twice with clean, warm water. Allow time
for drying before painting exposed surfaces. CAUTION: Caus-
tic soda will burn the skin, so as a precaution the workers must
use rubber gloves and safety goggles.
Combined Fungicidal Treatments.-Sometimes two or more
fungicidal treatments can be applied with good results while
still maintaining residues within legal tolerances. Dowicide A-
hexamine treatment and diphenyl pads can be easily combined,
as can two Dowicide A-hexamine treatments. This is very good
for: long shipments, fruit going into cold storage, fruit which
must wait between picking and packing, or fruit going into poly-
Fungicidal Waxes.-Solvent-type waxes are available with
Dowicide A alone or Dowicide A and diphenyl. Water emulsion-
type waxes are available with Dowicide A incorporated into the
wax formula. Both types of waxes when properly applied give
decay control. They should not be used on fruit that has been
previously treated with Dowicide A because of the danger of
exceeding the established residue tolerance.
Labeling Fungicide-Treated Citrus.-Containers (boxes, car-
tons, bags) filled with fungicide-treated citrus must be labeled
to comply with the Federal Food and Drug Administration re-
quirements. A typical label might read:
"Sodium o-phenylphenate used as a fungicide."
GRADES AND GRADING
Maturity.-According to the Florida Citrus Code of 1949, as
amended, all citrus fruit that is marketed must be mature. To
be mature, an orange must show 50 percent natural color break
(Parson Brown variety requires a 25 percent color break), and
contain more than 41/. gallons of juice per box. Additionally,
the juice must contain not less than 9 percent total soluble
solids, and must meet the sliding scale requirements for solids:
acid ratio (see the Florida Citrus Code). The standards for
grapefruit, tangerines, Temples, tangelos, and Murcotts are
slightly different. Tests are run on 10 fruit samples from each
size (five fruits for grapefruit). If the sample does not meet
the requirements (Regulation 1, Florida Citrus Commission),
the fruit is destroyed.
Better Handling of Florida's Fresh Citrus Fruit 29
Grades.-The U. S. Department of Agriculture standards and
grades are based on external size, appearance (blemishes, discol-
orations, scars), fruit shape, and type. The standards recog-
nized are Fancy, U. S. No. 1 Bright, U. S. No. 1, U. S. No. 1
Bronze, U. S. No. 1 Golden, or U. S. No. 1 Russet; U. S. No. 2
Bright, U. S. No. 2, U. S. No. 2 Russet; and U. S. No. 3. A tree-
run grade is recognized by Florida Citrus Commission regula-
tions and is unclassified.
Graders hand-sprt the fruit as it travels across a roller con-
veyer and place each grade on a separate belt (Fig. 15). Splits,
rots, and injured fruit go to the cull bin. Blemished but other-
wise sound fruit (eliminations) are sent to the processing plant.
Graders usually wear cotton gloves to prevent fingernail in-
juries to the rind.
Fig. 15.-Grading citrus fruit at the grading tables.
Sizing.-After fruit has been graded, it is sized. Four types
of sizers are in general use: (1) longitudinal belt and roll sizers
with packing bins or roll-board tables, (2) central longitudinal
belt and roll sizers, (3) transverse sizers, and (4) tangerine
(tomato) perforated belt sizers.
The belt and roll sizer at the packing bin has been in use for
many years. Size adjustment can be changed quickly from
30 Florida Agricultural Experiment Stations
grapefruit to oranges to tangerines. The machine is capable
of fairly accurate sizing if properly adjusted.
The central sizers are of many types or variations, such as
transverse roll and drop roll. The different sizes drop through
onto canvas distribution belts and are transported to the pack-
The tangerine sizer consists of a belt or chain with certain
size holes or meshes in each section. The main disadvantage is
that each size requires a belt or chain, and to change sizes the
belt must be changed. It works better for the flat type fruits
than roller and belt sizers. It is used mostly for tangerines, tan-
gelos, mandarins, and Murcotts.
If sizers are operated at high speeds, fruit may bounce, in-
creasing injuries and decay. Also, the sizing is not as accurate
in high-speed operation.
PACKAGES AND PACKING
Packing.-Most of Florida's citrus fruits are place-packed by
hand from bins or roll-board packing stations (Fig. 16 and Fig.
17). The older packinghouses use bins for each size. Each bin
Fig. 16.-Workers hand-packing oranges off a roll-board. Note empty
box conveyer, box stands, and packed box conveyer. Rubber floor mat
lessens fatigue, but the roll-board is too high for these three ladies, which
increases fatigue. This could be corrected by building height racks for them
to stand on.
Better Handling of Florida's Fresh Citrus Fruit 31
is capable of storing several boxes of fruit. The packers pack
from the side rather than facing the bin as they do with the
roll-board stations. The roll-board is more efficient and less tire-
some to packers, but fruit is only one layer deep. Therefore, little
fruit can be stored and, unless there are enough packers, fruit
can pile up and spill over on the floor. Some houses have deep-
ened the roll-board to avoid this disadvantage, but this lessens
the efficiency of packing. Ultimately, some baffle system will
probably be devised for fruit storage. The under-the-bin packed
box conveyers will be kept because of their efficiency.
Fig. 17.-The packing area of a large house, showing three roll-boards
and the empty box conveyer. Note fiberboard cartons and wirebound boxes
on the empty box conveyer.
Some machine-packing is done using count or weight. Poly-
ethylene film or mesh bags, 5- or 8-pound sizes, are the contain-
ers most used in machine packing, although some fruit is packed
in -,-bushel corrugated containers. The reason for the small
number of cartons or boxes being machine-packed is that each
container usually requires a different filling machine just as each
requires different closing machines. The fillers for bags can
handle most of the sizes used. Probably more machine-filling
would be done in Florida if labor costs were higher or fewer
types and sizes of containers were used.
32 Florida Agricultural Experiment Stations
Containers.-Most Florida citrus is packed in -4/ or 1%-
bushel wirebound boxes or in -%-bushel corrugated containers.
Most of the remaining fruit goes into 5- or 8-pound poly or mesh
bags (Fig. 18). These are shipped with or without master con-
tainers (wirebound or paper). However, several different types
of consumer packages appear each year-tray packs, vue packs,
cello-packs, tubes, plastic mesh bags, shrink packs, etc. Each
consumer package requires a packaging station, special opera-
tions, a master container, and a distribution line to and away
from the machine. This adds greatly to the distribution prob-
Container standardization on two or three types of containers
or less would help solve these problems, increase the efficiency
of house operation, and reduce the overhead and operating costs.
Standardization will come slowly, because managers are quite
willing to use any container the customer prefers.
PRECOOLING AND STORAGE
Precooling.-Citrus fruit is often delivered from the grove
at relatively high temperatures, especially during the hot weath-
er early and late in the season. Packinghouse processes such as
Fig. 18.-One type of bagging equipment used for placing fruit
in polyethylene film bags.
Better Handling of Florida's Fresh Citrus Fruit 33
degreening, color-adding, and drying contribute further heat to
the fruit. In addition, the natural heat of respiration may cause
an appreciable increase in the temperature of large masses of
The value of refrigeration in extending the shelf life of citrus
fruits has long been recognized. Shipment to market in railroad
cars or trucks which are cooled with ice or mechanical refrigera-
tion is common practice. Cooling of full loads of warm fruit
under these conditions is slow and inefficient, so some method of
precooling is desirable.
Special stacking patterns for cars and trucks that permit bet-
ter circulation of air around the fruit improve the cooling rate
for wirebound crates and ventilated cartons. Portable units hav-
ing high refrigeration capacity and air flow are sometimes at-
tached at the door of the loaded vehicle for several hours to pre-
cool the load of fruit before shipment. Some packinghouses place
packed fruit in refrigerated rooms overnight before loading,
but this type of cooling is inefficient, and rooms with sufficient
capacity for a day's pack are too expensive to be practical for
It is possible to cool citrus fruits before packing with either
cold air or water. Low heat capacity and poor heat transfer
require exposure to large volumes of air to cool citrus fruits.
Most packinghouses do not have enough room for sufficient line
length to fully cool the fruit with air; this method is better
adapted to a batch process using bins or pallet boxes in cooling
towers or tunnels. Fruit which has been treated with Dowicide
A-hexamine followed by air precooling shows outstanding keep-
ing qualities, even when stored later at higher temperatures.
The high heat capacity of water combined with more rapid
heat transfer makes hydrocooling of citrus fruit possible as a
continuous process in the packinghouse line. Several Florida
packinghouses are using this method commercially. Equipment
consists of a trough through which the fruit is conveyed while
a pump circulates large volumes of chilled water (33 to 350 F)
around the fruit. Time required for cooling is normally 20 to
30 minutes. -,
Work at the Citrus Experiment Station showed that fruit
which had been hydrocooled and later stored at 70 F frequently
had higher decay than non-precooled fruit. Use of 0.1 percent
Dowicide A in the cooling water at a pH of 10.5 and storage
under continuous refrigeration at 500 F improved the keeping
quality of hydrocooled fruit. Further experiments showed that
34 Florida Agricultural Experiment Stations
decay was directly proportional to time of exposure and temper-
ature of the water rather than due to the shock of rapid cooling.
Indications are that hydrocooling makes the fruit very turgid
and more easily injured in subsequent handling, resulting in
more decay by mold.
Hydrocooling can be quite useful for oranges which are to
be packed in cartons or in polyethylene bags in master cartons.
For best results, Dowicide A should be used in the cooling water,
and packed fruit should be kept under refrigeration until con-
sumed. This process is not as useful for grapefruit, since they
cool more slowly due to the insulating effect of the thick peel
and large size. With tangerines, water damage is often greater
than any benefits provided by hydrocooling.
Storage.-Fruit in the early stages of maturity is usually
best stored on the tree. Fruit of advanced maturity usually does
not store well for long periods of time.
The best relative humidity for all citrus fruits is about 90
percent. Lower humidities favor rind breakdown and shrivel-
ing, and higher humidities favor mold growth.
Grapefruit storage temperatures depend upon the time the
fruit is harvested, mainly because certain decay fungi are more
common at certain times of the season. The best temperature
is usually a compromise between that for decay control and that
which will avoid pitting-a storage temperature that will give
the least total economic loss. Diplodia stem-end rot is more com-
mon in the fall and summer, and temperatures of 50 to 550 F
limit its growth. Green mold growth is also slowed at 500 F.
However, if fruit has been handled roughly while being har-
vested, decay will be high, and 32 to 34 F will be a better stor-
age temperature. In the winter and spring, Phomopsis stem-
end rot is more common, and 32 to 34" F storage is necessary if
decay is high. At 32 to 34 F, some pits develop, but they are
smaller and not brown in color like those which occur at 40 F.
If pitting is bad, 50 to 60 F is the best temperature. Pitting
is more common on early grapefruit generally. They can be
stored for 4 to 6 weeks.
Oranges are not troubled much with low temperature rind
pitting, so the best storage temperature is 32 F. They can be
stored for 4 to 8 weeks without too much spoilage.
Limes are best stored at 48 to 50" F and may be held up to
6 weeks. Lower temperatures, however, induce pitting and sty-
lar end breakdown.
Better Handling ot Florida's Fresh Citrus Fruit 35
Lemons, when picked dark green in color, can be stored for
long periods of time at 55 to 58' F (1 to 4 months). Terminal
markets generally use 50 to 55W F.
Tangerines cannot be stored for long periods of time because
of the nature of the fruit. The temperatures recommended are
31 to 380 F. Tangerines do not hold over 4 weeks at the most.
Long storage at low temperature may result in watery break-
down, stylar end breakdown, brown staining, pitting, and other
physiological disorders. Freezing of the fruit usually occurs at
about 28.5 to 29 F. Damage is most likely to occur at the bot-
tom of the stacks or near the cold air entrance. If circulation is
too rapid, increased shrinkage (weight loss) may occur.
The use of Dowicide A-hexamine solution and diphenyl pads
greatly reduces decay losses in refrigerated storage. The stor-
age life is also extended considerably. For example, oranges can
be kept 3 or 4 months with slight decay loss at 30 to 34' F.
Grapefruit can be kept 2 or 3 months with some loss. Decay of
lemons, tangerines, and other citrus fruit is greatly reduced by
fungicides and good refrigeration.
Fruit intended for long storage should be picked in the mid-
dle of the season for that variety, handled carefully to minimize
wounding, processed promptly and carefully (treated with fun-
gicides and wax), and stored at the lowest advisable tempera-
ture. In general, the lower the temperature, the longer fruit
can be stored with less shrinkage and less decay.
HOW PACKING AFFECTS THE FRUIT
Fruit are living organisms while on the tree and continue to
live after harvest, taking up oxygen and giving off carbon di-
oxide, water, and heat. This process is known as respiration,
and a measure of these rates is an indication of the living rate.
In an ideal situation, any handling practices that increase
the respiration rate should be avoided. High temperature and
rough handling of fruit increase the rate of respiration and may
affect the external appearance. The external appearance of
citrus fruit is important in consumer appear, as is internal
quality and storage life. If the appearance is not satisfactory,
the fruit will simply not be sold.
Considerable progress can be made in marketing higher
quality fruit if the handling practices proved by experimental
work and common sense are followed. Some of the common bad
handling practices are listed and should be guarded against. Re-
36 Florida Agricultural Experiment Stations
search results justify these recommendations; however, no data
are presented here in the interest of brevity. This is not a com-
plete list and is given here as a guide.
I. Bruising Fruit
A. Dropping fruit more than 12 inches causes an increase
in the respiration rate and a shorter shelf life of the
1. The picking and loading operation appears to be
the biggest offender.
2. Unloading at the packinghouse and the packing-
house belt should be checked for rough handling.
Dropping upon other fruit or padding is preferred
to a hard surface, but the drop should be reduced
to a minimum.
B. Loading fruit to excessive depths causes pressure
1. Unsprung field trailers and excessive speed on
rough roads increase pressure bruises.
2. Overfilled field boxes often result in injury and
pressure bruises when the filled boxes are set on
top of one another when being loaded.
II. Peel Abrasions and Punctures
A. Boxes in poor condition, having sharp edges, splint-
ers, broken straps, etc., should be repaired.
1. Sand in the bottom of boxes adds to peel abrasions.
2. Sharp corners in the packing line can' be seen in
many houses and should be eliminated.
3. Fruit should not be allowed to remain on the
brushes too long at the beginning or end of a fruit
lot or for any other reason.
III. Fruit should not be exposed to direct sunlight or to high
temperatures in the field after harvest or while standing
at the packinghouse.
A. Increased temperature raises the rate of respiration
(180 F increase in temperature doubles the rate).
The heat of respiration adds to the temperature of
fruit. This can be serious when fruit loads remain
standing in the field or on the packinghouse floor for
Better Handling of Florida's Fresh Citrus Fruit 37
B. Excessive sunlight may burn or bleach the fruit sur-
face and increase the fruit temperature.
IV. The fruit is firmer under humid conditions and more easily
injured. Picking during the early morning hours or after
rains while the fruit is still wet should be avoided. Pick-
ing fruit that is dry reduces peel injury and decreases
humidity in the container, thus reducing the probability
V. Build-up of carbon dioxide should be avoided.
A. When fruit is stored in a closed container such as the
degreening room or an unvented polyethylene bag or
box liner, there is a possibility of build-up of carbon
dioxide to greater than 1 percent. This build-up de-
pends upon temperature, as previously mentioned.
Concentrations above 1 percent can result in off-
flavors, and may stop degreening action in degreen-
Bowman, Earl K. 1961. An improved place-packing station for citrus
fruit. U S. Dept. Agr., AMS-447.
Capel, George L. 1959. Comparative costs of alternative methods for
performing certain handling operations in Florida citrus packing-
houses. Fla. Agr. Expt. Sta. Bul. 609.
Davis, Paul L., and Paul L. Harding. 1963. Factors affecting rind break-
down of citrus fruits. U. S. Dept. Agr. MRR-596.
Florida Citrus Commission, Citrus Expt. Sta., and AMS, U. S. Dept. Agr.,
1959. Recommendations for control of decay in fresh citrus fruit.
Florida Citrus Commission and Citrus Expt. Sta. 1962. Better handling
of fresh citrus fruit.
Grierson, W. 1962. Handling Florida oranges in pallet boxes-an interim
report. U. S. Dept. Agr. MRR-529.
Grierson, W., and W. F. Newhall. 1953. Should gassing of Temples be
banned? Citrus Mag. 16 (2): 30-31, 35.
1960. Degreening of Florida citrus fruits. Fla.
Agr. Expt. Sta. Bul. 620.
Grizzell, William G. 1962. A device for forming two piece telescoping
cartons. U. S. Dept. Agr. AMS-490.
.1963. Filling polyethylene film bags with citrus
fruit. U. S. Dept. Agr. AMS-503.
Hopkins. E. F., and A. A. McCornack. 1958. Prevention of rind break-
down in oranges. Citrus Mag. 21 (3): 18-23, 25.
S1959. Methods for the control of decay in oranges.
Citrus Mag. 22 (4): 8, 10-11, 26, 30-31.
1961. Effect of delayed handling and other factors
on rind breakdown and decay in oranges. The Citrus Industry 42
(3): 9-10, 12, 14.
38 Florida Agricultural Experiment Stations
Knorr, L. C., R. F. Suit, and E. P. DuCharme. 1957. Handbook of citrus
diseases in Florida. Fla. Agr. Expt. Sta. Bul. 587.
Pratt, R. M. 1958. Florida guide to citrus insects, diseases and nutri-
tional disorders in color. Fla. Agr. Expt. Sta.
Prosser, D. S., Jr., W. Grierson, Eric Thor, W. F. Newhall, and J. K. Sam-
uels. 1955. Bulk handling of fresh citrus fruits. Fla. Agr. Expt.
Sta. Bul. 564.
Redit, W. H., and A. A. Hamer. 1961. Protection of rail shipments of
fruits and vegetables. U. S. Dept. Agr. Handbook 195.
Rose, Dean H., Charles Brooks, C. O. Bratley, and J. R. Winston. 1953.
Market diseases of fruits and vegetables, citrus and other subtropical
fruits. U. S. Dept. Agr. Misc. Publ. 498.
Smith, Roy J. 1963. The rapid pack method of packing fruit. Calif. Agr.
Expt. Sta. Cir. 521.
Soule, M. J., Jr., and F. P. Lawrence. 1959. What every citrus grower
should know-maturity tests for fresh fruit. Fla. Agr. Extension
Service Circ. 191.
Spurlock, A. H. 1963. Costs of picking and hauling Florida citrus fruits
1961-62 season. Fla. Agr. Expt. Sta. Agr. Econ. Mimeo Report 63-7.
Spurlock, A. H., and H. G. Hamilton. 1963. Costs of packing and selling
Florida fresh citrus fruits, 1961-62 season. Fla. Agr. Expt. Sta.
Agr. Econ. Mimeo Report 63-9.
Thor, Eric. 1959. Economies of scale in the operation of Florida citrus
packinghouses. Fla. Agr. Expt. Sta. Bul. 606.
Ting, S. V. 1955. Determination of artificial coloring agents on oranges
and in orange products. Proc. Fla. State Hort. Soc. 68: 157-160.
Wells, Arthur W. 1962. Storage temperature and humidity on loss of
weight by fruit. U. S. Dept. Agr. MRR-539.
Winston, J. R. 1950. Harvesting and handling citrus fruits in the Gulf
states. U. S. Dept. Agr. Farmers' Bul. 1763, Rev.