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preventing fruit rot development during storage and in the
marketing channel.  Good postharvest treatments will
insure the consumer of a highly desirable product.
Hydrocooler Treatment
Fruit in bulk bins should be hydrocooled as quickly
as possible before placing in cold storage. The
hydrocooler water should contain one of the chlorine-
generating products at 100 ppm to kill spores and fungal
mycelium on the fruit surface. This treatment will
sterilize the fruit surface but provides no residual fungicide
protection. A Supplement Label must be in hand to use
these materials.
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Research conducted at Clemson University,
University of California, and Rutgers University has
shown that any operation which causes a peach to rub,
roll, or physically abrade against another peach can result
in discoloration.
Inking has also been triggered by iron (in excess of
10 PPM) in the hydrocooler and dumptank water, leachate
from latex-rubber drying rollers, excessive brushing or
vibration, ammonia, and fungicide sprays.
Research to date has resulted in these suggestions for
control:
[!]Avoid any operation that causes excessive vibration,
rubbing, or rolling; reduce operations that cause
bouncing from the orchard to the packinghouse.
[!]Keep field bins, held outside the packinghouse prior
to hydrocooling, in a shaded area out of sunlight.
[!]Remove "field heat" as soon as possible. Fruit
temperatures, out of the field, can range from 75oto
95oF. Remove field heat with a hydrocooler rather
than attempting to remove it with a ventilated cold
room.
[!]Keep hydrocoolers and dumptanks as clean as
possible. Excessive iron in treatment water can cause
discoloration. Failure to clean hydro coolers and
dumptanks properly can result in high levels of rust
in the water, thus increasing discoloration. Drain and
refill with fresh water on a regular basis.
[!]Maintain the pH of water in hydrocoolers and
dumptanks between 6.5 and 7.0. Water at a pH of 4.0
and 6.0 has caused problems with discoloration.
Proper pH also reduces iron levels.
[!]Check equipment for a loss of ammonia. Leaks in the
refrigeration system can also stimulate inking.
Peaches can be affected by ammonia at levels under 1
PPM - below levels that emit an odor.
Recommendations for Water Treatment
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Packing Line Treatment
During the packing operation, fruit should be sprayed
with Rovral 50WP using 2 pounds per 100 gallons of
solution, with or without wax. One hundred gallons of
spray should treat 200,000 pounds of fruit. If growers
possess Botran 75WP with a label for postharvest use,
add 1/3-1/2 pound of Botran to the solution
Postharvest Peach Skin Discoloration
and Its Control
Skin discoloration (also known as inking, ink spot,
black spot, streak, or purple spot) is a disorder of peach
which has been observed in New Jersey for more than 20
years. No disease-causing organism can be isolated from
affected fruit. The initial symptoms are development of
burgundy-colored areas within the red flesh of the peach.
These areas eventually turn purplish-black or ink color.
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