GRIERSON, McCORNACK, HAYWARD
AGRICULTURAL EXTENSION SERVICE
UNIVERSITY OF FLORIDA
W. Grierson,2 A. A. McCornack,3 and F. W. Hayward2
"Sales appeal" is of more critical importance for Florida tan-
gerines than it is for oranges and grapefruit. Although total tan-
gerine production seldom exceeds 5,000,000 boxes, some tangerines
are usually unsold because the crop cannot be moved in the limited
Not only is the shipping season sharply limited by heavy con-
centration on the short-season Dancy variety but, within that
season, maximum volume can only be moved on the Thanksgiving
and Christmas markets. If outbreaks of decay and peel injuries
cause buyer resistance, there is little opportunity for the market
Decay can be reduced and sales appeal improved by utilizing
the results of recent research on tangerine handling. This research
continues, but enough has been learned of the complex relation-
ships among growing conditions, reaction to ethylene degreening,
and holding quality to formulate a program for better tangerine
arrivals and improved shelf life.
In applying these recommendations it must be remembered
that not only are tangerines naturally more fragile than oranges
and grapefruit, but in addition they are more sensitive to grove
conditions, such as sudden increases in soil moisture after periods
Water Stress.-Tangerines are particularly subject to break-
down when heavy rains or heavy irrigation follow a period of
severe drought. At this time, ethylene degreening can sometimes
make the tangerines so sensitive that they become too frail to
wash, dry, wax, and pack without excessive losses. They often
become increasingly difficult to handle for as many as four days
after a rain or heavy irrigation. During this period internal
weakness may cause fruit drop. Fruit that remain on the tree
recover and may be picked later with no more than normal loss.
Typical water stress damage shows up on arrival at the market
as increased decay and peel injury. "Zebra skin" injury (cover
photo), in which the peel over the segments darkens, usually does
not appear until several days after shipping. It is seldom seen
Based on results of cooperative research by the University of Florida
Citrus Experiment Station and the Florida Citrus Commission.
2 Associate Chemist and Associate Biochemist, Citrus Experiment Sta-
SAssistant Horticulturist, Florida Citrus Commission.
in the packinghouse. Small sizes are particularly subject to
"zebra skin" peel injury, with subsequent high rates of decay.
Wet Fruit.-Oil cells of wet fruit are very subject to mechani-
cal damage resulting in oleocellosis, the condition in which released
peel oil causes a dark blemish on the peel. Tangerines should
not be picked while wet; but, if rain interrupts picking, handle
the wet tangerines with extreme care. When such wet tangerines
reach the packinghouse, do not attempt to dry them. Start de-
greening immediately, as described below, and injury will be
Picking and Degreening
Color Break.-Pack-out is low in tangerines picked without
a good color break. A long degreening time increases decay and
sharply reduces the volume of fruit that can be handled through
the packinghouse. It can be profitable to pay pickers to spot pick
for color in order to get the maximum number of packed boxes per
grove and per hour of packinghouse operation.
Pulling or Clipping.-Tangerines should be clipped.
Hauling.-Tangerines should be hauled to the packinghouse
as soon as possible after picking. Do not expose fruit to direct
sun if it can be avoided.
Degreening.-Degreening shortens the shelf life of tangerines.
The peel is sensitized to handling damage, particularly brushing
injury. Shorten degreening time by picking tangerines with a
good color break and degreening correctly. Avoid degreening
periods of more than 48 hours. Keep humidity high. The differ-
ence between wet and dry bulb thermometer readings should be
2 to 3 degrees or less. Ethylene gas should be used at no more
than one bubble per minute per 10 boxes of room capacity.
Do not "air or "harden" after degreening. If the color is
well developed before the tangerines are to be packed, turn off the
heat and ethylene, keep the room closed, with the fan running
and the humidity high, until the fruit is to be packed.
Handling on the Packing Line
Keep brushing to an absolute minimum. Ethylene-degreened
tangerines are particularly susceptible to brushing injury.
Washing.-Washer brushes should be wet before using and
lubricated with soap or detergent.
Drying. Roller driers are preferred for tangerines. Hot
polisher-driers are very injurious and a major cause of "lifeless
looking" tangerines on the market, often with "zebra skin" injury.
Keep the temperature of the driers at 1400 F or lower and brush
speed at less than 150 rpm.
Tangerine decay is not as easy to control as decay of oranges
or grapefruit. Fungicidal treatments are of some value when used
Dowicide A-hexamine treatment reduces decay, particularly
if the tangerines have been handled correctly. It cannot eliminate
losses due to previous improper handling.
Two diphenyl pads can be used in a ventilated half-box con-
tainer without exceeding the legal tolerance. They should be
placed between layers of fruit for best results. Tangerines absorb
diphenyl much more readily than do other types of citrus fruit.
If more than two pads are used, tolerance may be exceeded unless
the fruit is handled under refrigeration.
Well-ventilated containers are essential for tangerines. Wire-
bound boxes are suitable, but should not be "bulge packed".
Cartons or fiber board-plus-wood containers are acceptable only
if very well ventilated.
Prompt cooling after packing is important, particularly for long
shipment or with very ripe tangerines. Tangerines can be held
at 320 F with good results. Shipping temperatures should be
50 F or lower.
Both handling speed and refrigeration are important. Tan-
gerines should be shipped under refrigeration by the fastest carrier.
Loads should be stacked in the truck or rail car to make the most
effective use of the cooling equipment.
Avoid picking under extreme "water stress" conditions.
Spot pick for color.
Degreen for a minimum length of time and with high
Handle quickly and gently; cool promptly.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, Univerity of Florida,
Florida Stale University and United States Department of Agriculture, Cooperating
M. O. Watkins, Director