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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Physical Means 203
5% even when low ethanol concentrations (2.5-5%) were used. Spore
mortality of M fructicola and K stolonifer, the main postharvest
pathogens of peaches and nectarines, occurred much more quickly in
heated ethanol than in heated water (Margosan et al., 1997): a 10%
ethanol solution at 46 or 50°C greatly reduced the LT95 (95% lethality) of
both fungi (Table 12).
TABLE 12
Estimated time (seconds) to kill 95% of the spores of Monilinia
fructicola or Rhizopus stolonifer in water, alone or containing
10% ethanol, at 46 or 50°C*
M. fructicola R. stolonifer
Treatment 46^C 50^C 46^C 50°C
Water 734.0a 206.3a >1000.0a 410.3a
10% ethanol 57.4b 7.0b 94.4b 46.3b
* Values followed by unlike letters are significantly different (P < 0.05).
Reproduced from Margosan et al., 1997 with permission of the
American Phytopathological Society.
When peaches and nectarines, infected with M fructicola spores, were
immersed in 10% ethanol at 46 or 50°C, or 20% ethanol at 46''C the
incidence of decayed fruit was 83, 25 or 12%, respectively, i.e., similar or
a better control was achieved than that following a 1-min dip in the
fungicide, iprodione (1000 |ag ml^). No injury to the fruits occurred and
no off-flavors were detected in the fruits. However, unlike fungicides, the
hot ethanol treatments did not deposit persistent antifungal residues, so
there was a lack of continuous protection of the fruits from
recontamination.
The increases in spore mortality and decay control - occurring when
hot water and ethanol were combined - may result from their affecting
the same sites in the spores. Since low concentrations of ethanol can
lower the temperature at which phospholipids undergo a phase change
(Rowe, 1983), the increases in spore mortality and decay control following
the addition of ethanol may have resulted from a lowering of the
phase-change temperature of the mitochondrial membranes of the spores
under these conditions (Margosan et al., 1997).
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