Biomedical Engineering Reference
In-Depth Information
many fruits is due to an increase of soluble pectin and corresponding decrease in
insoluble pectin. Klein and co-workers
108
postulated that in the case of “Anna”
apples, insoluble pectin was retained during storage and consequently a smaller
amount of soluble pectin and calcium pectate was found in the heated fruits. Lurie
and co-workers
166
used conditioning at 38°C for 4 days to control superficial scald,
a chilling injury symptom on “Granny Smith” apples. This treatment can be used
to substitute chemical treatment using diphenylamine (DPA) by slowing down the
accumulation of
-farnesene and conjugated trienes in apple cuticle during short-
term storage. DPA inhibited the oxidation of
α
α
-farnesene without affecting its
accumulation.
Tomatoes develop chilling injury when kept below 12 to 13°C. This can be
prevented by keeping mature green tomatoes at a temperature of 36 to 40°C for
3 days before storage at 2 to 3°C for 3 weeks.
130
After storage, the fruits had a lower
potassium ion (K
+
) leakage and a higher phospholipid content than the unheated
fruits. The heat-treated tomatoes also ripened normally, although more slowly than
freshly harvested fruits. Chilling injury of unheated tomatoes was manifested by
failure to turn red and the development of brown areas under the peel. Lurie and
Klein
130
postulated that heat stress caused an inhibition of ripening and that this
inhibition was maintained at 2.5°C and removed only after transfer to 20°C. They
also found that heat stress inhibited the loss of phospholipids leading to a lower rate
of potassium leakage and gave protection against chilling injury.
D
ELAYED
C
OOLING
One way of reducing the susceptibility of the produce to chilling injury is to condition
the commodity at a temperature higher than the intended storage temperature. Chill-
ing injury in lemons can be prevented by temperature-conditioning the fruits at 10,
15, 21, or 27°C immediately before storage at 1°C. Conditioning at 27°C for 7 days
caused the least chilling injury but McDonald
116
did not recommend this because of
the large variations in response of lemons harvested in different years and within
treatments. The susceptibility of cucumber to chilling injury when stored at 5°C for
4 or 6 days was reduced by conditioning at 12.5°C.
167
Lacatan bananas can be less
sensitive to chilling injury by lowering the temperature at steps of 3°C at 12-h
intervals.
168
Cold treatment is one of the approved quarantine treatments of pink
grapefruit (
Citrus paradisi
) for export to Japan. The approved time-temperature
regimes for cold treatment are 0.6°C for 11 days, 1.1°C for 12 days, 1.6°C for
14 days, or 2.2°C for 17 days.
169
Cold treatment for carambola is at 1°C for 15 days.
74
Chalutz and co-workers
170
suggested the conditioning of grapefruit, prior to cold
treatments, by storing the fruit at 16°C and relative humidity of 90 ± 5% for 7 days.
Miller and co-workers
114
subjected grapefruits that were either waxed or film-
wrapped and treated with thiabendazole (TBZ) to high temperature conditioning at
31°C for 3 days. After storage at 1°C for 4 weeks, chilling injury developed in all
treatments but was drastically reduced in film-wrapped fruits. TBZ caused a slight
reduction on chilling injury symptoms. Rind scald or pitting of conditioned fruit,
which are symptoms of chilling injury, were not eliminated but were drastically
reduced in film-wrapped fruits conditioned at 7°C or at 16°C.
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