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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Physical Means 217
The feasibility of a combination process involving gamma irradiation,
packing in closed polyethylene bags and biological control of rot-causing
fungi was evaluated as a means of extending the shelf life of fresh ginger
rhizomes at ambient temperatures (25-30°C) in India (Mukherjee et al.,
1995). The recommended procedure consisted of dipping rhizomes, which
had previously been washed and dried, in a spore suspension of a
Trichoderma sp. isolated from sclerotia of Sclerotium rolfsii (the major
pathogen during extended storage) along with other antagonistic
microorganisms. The next steps included air-drsdng, packing in chosen
low-density polyethylene bags and irradiation at 60 Gy. The treated
ginger rhizomes remained in good marketable condition for up to 2
months at ambient temperatures without sprouting (thanks to
irradiation at a sprout-inhibiting dose), showed suppressed decay
development (thanks to the protection of the rhizomes or the cut surface
of sliced rhizomes by the antagonistic Trichoderma isolate) and reduced
weight loss (thanks to storage in closed polyethylene bags).
Radiation Approval
Following extensive studies in recent decades of the "wholesomeness"
of irradiated food, the list of commodities approved for radiation by
health authorities in various countries has been considerably lengthened.
An important event took place in 1986 when gamma irradiation up to a
dosage of 1 kGy was approved by the Food and Drug Administration of
the United States, for treatment of fruits and vegetables. This has
accelerated both research and development in the use of ionizing
radiation as a physical means for postharvest life extension.
C. ULTRAVIOLET ILLUMINATION
Ultraviolet (UV) illumination is known to damage plant DNA and to
affect several physiological processes (Stapleton, 1992). However, a
special interest has recently been drawn to the ability of low doses of
UV-C light (wavelength of 190-280 nm) to induce disease resistance in a
wide range of fruits and vegetables.
A number of lines of evidence from various fruits and vegetables
(Wilson et al., 1994) indicate that the effect of UV-C is not solely due to
its germicidal activity: (1) tissue inoculated after UV treatment was more
resistant to invasion by the pathogen; (2) the UV effect was not always
correlated with increased UV doses. In addition, UV treatments have
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