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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
216 Postharvest Diseases of Fruits and Vegetables
pathogens but resulted in fruit damage (Brodrick et al., 1985); whereas
irradiation alone (2 kGy) controlled fungal development but resulted in
fruit softening. A combination of mild heat treatment (42°C, 10 min) with
low-dose irradiation (0.75-1.5 kGy) effectively controlled development of
Monilinia fructicola, Rhizopus stolonifer and Botrytis cinerea, with no
significant changes in fruit texture, aroma or taste.
Treating tomatoes with the combination of heating (50°C, 2 min) and
low-dose irradiation (0.5 kGy) totally eliminated Alternaria rot under
shelf-life conditions, but each of these treatments resulted in accelerated
softening of the fruit (Barkai-Golan et al., 1993b). Gamma irradiation
without hot water treatment reduced the incidence of bacterial soft rot
caused by Erwinia and Pseudomonas species (Spalding and Reeder,
1986a). In this case, the combination of heating and irradiation provided
no better rot control than irradiation alone.
By combining irradiation with fungicidal or fungistatic treatment it
was possible to reduce both the irradiation dose and the concentration of
the chemical compound. Moreover, since the suppressive effects of
irradiation and the chemical treatments may differ greatly among fungal
species, their combination might broaden the operational range against a
wide variety of microorganisms (Barkai-Golan, 1992).
Several studies have shown advantages in combining low-dose
radiation, mild heat treatment and chemicals, compared with the
double-component combined treatments, in controlling storage decay. Such
an advantage was recorded in apples for which the association of heating
(50°C, 10 min), irradiation (1.5 kGy) and benomyl (250 ppm), in this
sequence, inhibited development of the blue mold (Penicillium expansum)
under shelf-life conditions (Roy, 1975). For P. digitatum-inoculated
Shamouti oranges, the combination of radiation (200 Gy), diphenyl (15 mg
per fruit) and hot water dip (52°C, 5 min) extended the incubation period of
the green mold beyond the extension caused by heat and radiation or by
diphenyl and radiation (Barkai-Golan et al., 1977a). For Kensington Pride
mangoes, a hot benomyl dip prior to low-dose irradiation (0.3-1.2 kGy)
resulted in an additive effect which markedly improved the partial control
achieved by irradiation alone (Johnson et al., 1990).
A combination of gamma and ultraviolet radiation was found to be
effective against fungi sensitive to low gamma doses, such as
Phytophthora and Colletotrichum. In such cases, the combined treatment
facilitates the reduction of the ionizing radiation dose needed for fungal
inactivation (Moy et al., 1978).
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