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Practical Measures for Control of
Stem-End Rind Breakdown
A. A. McCornack and W. Grierson2
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 injury, 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 (button 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.
Symptoms vary with variety, with seasons, and with growing
conditions. The Pineapple variety, which is highly susceptible, is
also subject to a rind breakdown on the sides of the fruit. It may
or may not be caused by the same conditions that cause typical
stem-end rind breakdown. This trouble has occasionally been
noticed (in its earliest stages) on arrival at the packing house, 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 to know that this breakdown is
very closely associated with drying conditions, particularly
in the period between picking and waxing.
Ethylene gas does not cause stem-rind breakdown, but faulty
management of degreening rooms is often responsible. The
often-used description in the markets, "gas bur," for SERB
Cooperative research by the Florida Citrus Commission and the Florida
Citrus Experiment Station.
2 Assistant Horticulturist, Florida Citrus Commission, Lake Alfred, and
Associate Chemist, Florida Citrus Experiment Station, Lake Alfred,
The color-add process is not likely to cause rind breakdown
unless higher than recommended temperatures are used. How-
ever, the color-add dye stains the injured area heavily, making
the injury more obvious.
What We DO NOT Know About It
What makes a particular crop susceptible? Fertilizer and irri-
gation practices appear to be factors, but no single fertilizer
element controls stem-end rind breakdown. Factors such as
weather, variety, and maturity are also important but not yet
We do not know how susceptibility to various types of rind
injuries of oranges are related to each other and to the often
similar defects on grapefruit, tangerines, Temples, and tangelos.
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 levels because they
appear to be old and are certainly unattractive. Financial settle-
ments for rind damage appearing between the time of grading in
the packinghouse and arrival on the market are another important
factor. Further financial losses are caused by the greatly in-
creased amount of decay in oranges that have developed stem-
end rind breakdown.
You Can Reduce or Eliminate
Stem-End Rind Breakdown
Stem-end rind breakdown, as shown on the cover of this circu-
lar, can usually be avoided by following the instructions given
Do not attempt to "harden" oranges by any method such
as delayed handling, drying or unnecessary ventilation. Fruit
on the tree does not have stem-end rind breakdown. Keep fruit
as near tree firmness as possible.
Keep fruit in shade after picking.
Shorten the period between picking and waxing by all
reasonable methods, particularly during dry, hot, or windy
Cover loads of fruit with a canvas, especially when long
hauls are involved. Do not use transparent plastic; it traps the
Degreening rooms should be humid, but the fruit should
not be wet. Wet fruit may develop another type of peel injury.
Relative humidity should be 88 to 96 percent. For practical
purposes, this means maintaining no more than a 2 to 3 degree
difference between wet and dry bulb thermometers,
Some ventilation of degreening rooms is essential to prevent
accumulation of carbon dioxide given off by the fruit. However,
periodically opening the rooms for airing causes fruit to dry and
increases the risk of rind breakdown. Continuous ventilation is
recommended. Rooms with a fresh air ventilation inlet should be
set to pull in approximately 2 percent per minute of the total
volume of air in the degreening room. With canvas-sided rooms,
enough ventilation is often obtained by leaving the canvases an
inch or so above the floor.
Fan capacity should be adequate so there are no dead air
spaces in the degreening room. Excess air speed tends to dry
It is best to process and pack oranges immediately after de-
greening. If this cannot be done, turn off the heat and ethylene
but leave the fans on. Keep the room closed and the relative
humidity above 88 percent.
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 88 percent.
Do not worry about increased decay due to high humidity.
The best protection against decay is to avoid rind breakdown.
Avoid excessive brushing. Polisher-driers are particularly
damaging if run too hot or with excessive 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
Before packing, oranges should receive a good, even coat of
wax. This protects them against unnecessary water loss. Ex-
cessive wax application can cause off-flavors by reducing respira-
The Florida Citrus Commission and the University of Florida
maintain a continuing program of research on stem-end rind
breakdown and other post-harvest diseases.
The above information is based on findings from this research
program. Much of this research has been published in scientific
papers. References (and reprints of some of these) are available
from the Harvesting and Handling Section, Citrus Experiment
Station, Lake Alfred, Florida.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30. 1914)
Agricultural Extension Service, University of Florida,
Florida State University and United States Department of Agriculture. Cooperating
M. O. Watkins. Director