ru.s Station Mimeo Report CES 65-11
(In Cooperation with Florida Citrus Commission)
STEM-END RIND BREAKDOWN
A. A. McCornack and W. Grierson
Note: This is a special prepublication issue by
request of the Florida Fresh Citrus Shippers
Association. Copies without the color photo-
graph may be had by writing to the authors at:
Harvesting and Handling Section
University of Florida Citrus Experiment Station
Lake Alfred, Florida 33850
STEM-END RIND BREAKDOWN OF ORANGES
A. A. McCornack and W. Grierson
Stem-end rind breakdown, as shown on the cover
of this circular, can usually be avoided by follow-
ing the instructions given here.
TO REDUCE OR ELIMINATE STEM-END RIND BREAKDOWN
1. DO NOT ATTEMPT TO "HARDEN" ORANGES BY ANY
METHOD SUCH AS DELAYED HANDLING, DRYING OR UNNECES-
SARY VENTILATION. Fruit on the tree does not have
stem-end rind breakdown. Keep fruit as near tree
firmness as possible.
2. Keep fruit in the shade after picking.
3. Shorten the period between picking and
waxing by all reasonable methods, particularly
during dry, hot or windy weather.
4. Cover loads of fruit with a canvas, espe-
cially when long hauls are involved. Do not use
transparent plastic; it traps the sun's heat.
5. Degreening rooms should be humid, but the
fruit should not be wet. Wet fruit may develop a
different type of peel injury. Relative humidity
should be 85-95%. For practical purposes, this
means maintaining a 2-30 difference between wet and
dry bulb thermometers.
Assistant Horticulturist, Florida Citrus Commission,
Associate Chemist, Citrus Experiment Station,
6. Some ventilation of degreening rooms is
essential to prevent accumulation of carbon dioxide
given off by the fruit. Periodically opening the
rooms for airing causes drying of the fruit, there-
by increasing the risk of rind breakdown. Contin-
uous ventilation is recommended. Rooms with a
fresh air ventilation inlet should be set to pull
in approximately 2% of the total volume of air in
the degreening room per minute. With canvas-sided
rooms, enough ventilation is often obtained by
leaving the canvases an inch or so above the floor.
7. Fan capacity should be adequate so there
are no dead air spaces in the degreening room.
Excess air speed tends to dry fruit.
8. It is best to process and pack oranges
immediately after degreening. If this cannot be
done, turn off the heat and ethylene but leave the
fans on. Keep the room closed and the humidity
above 85% RH.
9. If fruit does not need degreening but must
be held overnight, or longer, before processing and
packing, keep the temperature low and the humidity
high. The best way to do this is to put the fruit
in a closed degreening room without heat or ethylene
but with fans operating and the relative humidity
above 85%. DO NOT WORRY ABOUT INCREASED DECAY DUE
TO HIGH HUMIDITY. THE BEST PROTECTION AGAINST DECAY
IS TO AVOID RIND BREAKDOWN.
10. Avoid excessive brushing. Polisher-driers
are particularly damaging if run too hot or with
excessive brush speeds. Brush speed should be no
faster than 200 rpm. All brush equipment should be
equipped with automatic "wipe-outs" so fruit cannot
"idle" on the brushes.
11. Before packing, oranges should receive a
good, even coat of wax. This protects them against
unnecessary water loss. Excessive wax applica-
tion can cause off-flavors by unduly checking
WHAT IS STEM-END RIND BREAKDOWN?
Stem-end rind breakdown (SERB) is the most
common of the various forms of peel injury that
affect oranges. This breakdown causes considerable
financial loss to shippers and handlers, not only
in Florida, but almost everywhere in the world
oranges are grown commercially, particularly in
the more humid areas.
Stem-end rind breakdown is known by many
names: brown stem, burnt stem, stem-end peel in-
jury, aging, and gas burn. It can occur on all
varieties of oranges, but Hamlin and Valencia
oranges develop the most typical symptoms.
Stem-end rind breakdown first appears as a
collapse of the rind cells at the stem end (but-
ton end) of the fruit. Usually, a narrow ring of
cells around the button remains normal in appear-
ance. The areas of breakdown gradually increase,
tending to run together and darken in color. Symp-
toms vary with variety, with seasons and with growing
conditions. The Pineapple variety, which is highly
susceptible, is also subject to a similar breakdown
on the sides of the fruit that may or may not be
caused by the same conditions that cause typical
stem-end rind breakdown. This trouble has occa-
sionally been noticed, in its earliest stages, at
the time of picking, but it is much more common
for typical symptoms to develop between two and
seven days after picking.
WHAT WE DO KNOW ABOUT IT
We know how to reduce or eliminate stem-end
rind breakdown on susceptible crops.
Small Sizes and Thin-Skinned Fruit
Typical stem-end rind breakdown is
most prevalent on smaller sizes and
on thin-skinned oranges.
It is particularly important that we
know that this breakdown is very closely
associated with drying conditions, par-
ticularly in the period between picking
Ethylene gas does not cause stem-end
rind breakdown, but faulty management
of degreening rooms is often responsible.
The often-used description in the markets,
"gas burn," for SERB is incorrect.
This process is not likely to cause rind
breakdown unless run at higher than rec-
ommended temperatures. However, the color-
add dye stains the injured areas heavily,
making the injury more obvious.
WHAT WE DO NOT KNOW ABOUT IT
What makes a particular crop susceptible?
Fertilizer and irrigation practices are
certainly factors, but no single fertilizer
element controls stem-end rind breakdown.
Factors such as weather, variety and matur-
ity are also important but not yet fully
We do not know how susceptibility to vari-
ous types of rind injuries of oranges are
related to each other and to the often similar
defects on grapefruit, tangerines, Temples,
WHAT IS THE IMPORTANCE OF STEM-END RIND BREAKDOWN?
Oranges with stem-end rind breakdown meet with
considerable buyer resistance at both wholesale and
retail because they appear to be old and are cer-
tainly unattractive. Cash settlements for damage
appearing between the time of grading in the packing-
house and arrival on the market are another important
factor. Further financial losses are caused by the
greatly increased amount of decay in oranges that
have developed stem-end rind breakdown.
The above information is based on many years
of experimental work. Much of it is published in
detail in scientific papers. (Those that are still
in print are available from the authors.)
Research on citrus rind problems continues at
the University of Florida Citrus Experiment Station,
Lake Alfred. Why are certain crops and types of
citrus more susceptible to stem-end rind breakdown?
Experiments are in progress to try to find the
Meanwhile, use the information given in this
circular to avoid or reduce losses caused by stem-
end rind breakdown.
A contribution from the
Harvesting and Handling Section
University of Florida
Citrus Experiment Station
Lake Alfred, Florida