Post harvest diseases fruits and vegetables - Xavier University ...

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Physical Means 197
cell culture (Lurie, 1998). By enhancing host thermotolerance, the HSP
synthesis which follows heat treatment may contribute to the possibility
of using higher, more effective heat exposures for heat-sensitive fruits as
well.
Induction of Resistance to Chilling Injury
Immersing citrus fruits in hot water for short periods was found to
reduce their sensitivity to cold-storage temperatures, thus reducing both
chilling injury and decay incidence during storage (Rodov et al., 1995a;
Wild and Hood, 1989). The addition of fungicides, such as thiabendazole
or imazalil, to the hot water (53°C, 2 min) can enhance the tolerance of
the fruit to low temperatures (McDonald et al., 1991; Wild and Hood,
1989), but even when this combination does not reduce chilling injury, it
enhances the decay control imparted by the hot water.
Electron microscopic examination of grapefruits which have been
immersed in hot water has revealed structural changes, and less
cracking in the fruit cuticle than in those of fruits which developed
chilling injury. Wrapping fruits which had previously been immersed in
hot water, in sealed plastic film enhanced their tolerance to chilling, but
was not essential for the success of the treatment (Rodov et al., 1995a).
Similarly to the short-term heat treatments (involving high
temperatures), long-term heat treatments (involving lower temperatures)
can also induce resistance to chilling injury in cold-sensitive fruits.
Mangoes, which are a tropical crop, are subject to chilling injury when
stored below 10°C (Couey, 1986). The symptoms of injury include rind
discoloration, pitting, uneven ripening, poor color and flavor, and
increased susceptibility to decay. However, when the fruits were kept at
38°C for 24 or 48 h before storage at 5°C for 11 days, chilling injury
symptoms were reduced, and the reduction was enhanced with increased
duration of the high-temperature treatment (McCoUum et al., 1993). The
most pronounced effect was reduction of the rind pitting and
discoloration that were apparent at the time of transfer from 5 to 21°C,
and which persisted during ripening.
Chilling injury is also characteristic of tomato fruits stored at
temperatures lower than 10-12°C. However, tomatoes exposed to 36-40°C
for 3 days did not develop chilling injury, and ripened normally following
storage at 2°C for 3 weeks (Klein and Lurie, 1991; Sabehat et al., 1996).
The resistance to low-temperature injury was found to be contingent on
the presence of HSP (Sabehat et al., 1996), but it may not be due solely to
the presence of HSP. Heat treatment may cause damage to the cell
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