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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Means for Maintaining Host Resistance 129
by decreasing the O2 concentration from 21% to 2.5% or raising the CO2
level from 0.03% to 10% (Biale, 1946; Young et al., 1962). Storing Florida
avocados for 45-60 days at lO'^C in an atmosphere of 2% O2 and 10% CO2
resulted in a remarkable reduction in anthracnose (Colletotrichum
gloeosporioides), the main cause of spoilage during storage and
marketing, and at the same time prevented chilling injury, which is
generally accompanied by increased susceptibility to fungal attack
(Spalding and Reeder, 1975). Since such concentrations of O2 and CO2
have only a slight inhibitory effect on the growth of C. gloeosporioides,
decay control in this atmosphere was attributed to maintenance of the
fruits in the firm mature-green stage and thus to the maintenance of the
quiescence of the fungus. In contrast to avocados, CA was only slightly,
or not at all beneficial to papayas, for which, similarly, decay is the chief
limiting factor in storage extension (Spalding and Reeder, 1974).
Atmospheres of 10-20% CO2 or more reduce the incidence of decay
caused by S. cinerea and Rhizopus stolonifer in several cultivars of
strawberries, as exhibited, not only during cold storage but also after
removal of the fruit to shelf-life conditions, without causing objectionable
off-flavors (Harris and Harvey, 1973). Under these conditions decay
suppression may be attributed both to the direct effect of the CA on the
pathogens and to its effect on the physiological deterioration of the fruit.
The resistance of the fruit to Botrytis and Rhizopus decay in a
C02-enriched atmosphere was hypothesized to be the result of the high
levels of acetaldehyde and ethyl acetate produced by fruit under such
conditions (Shaw, 1969). An atmosphere enriched with CO2, at 10, 15 or
20%, retarded storage decay of blueberries by 1-2 days after the berries
had been removed from the CA and held at 21°C, whereas an atmosphere
of 2% O2 was ineffective on its own in suppressing decay, and did not
enhance the effect of the CO2 atmosphere (Ceponis and Cappellini, 1985).
Decay suppression by high CO2 (20%) has also been recorded in
muskmelons after 14 days at 5°C followed by shelf-life conditions (Stewart,
1979), while CA (10-20% CO2 + 10% O2) along with ethylene absorbance
prolonged the storage life of Galia melons, through the maintenance of
tissue firmness and decay suppression (Aharoni et al., 1993a).
CA had considerable benefits over air for the long-term refrigerated
storage of white cabbage (Geeson and Browne, 1980): storing cabbage in
an atmosphere of 5-6% CO2 + 3% O2 at 0-2''C resulted in the retardation
of general senescence effects, such as yellowing, toughening and loss of
flavor, and in the inhibition of physiological disorders and the repression
of decay development during prolonged storage.
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