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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Means for Maintaining Host Resistance 121
2 days every 3 or 4 weeks reduced chilling injury symptoms in stored
nectarines (Anderson and Penney, 1975).
The time taken for an irreversible chilling injury to occur is usually
very short for perishable produce with short storage life, such as
cucumber or zucchini squash. Therefore, intermittent warming of these
commodities must be applied earlier and more frequently (Cabrera and
Saltveit, 1990; Wang, 1993).
B. MODIFIED AND CONTROLLED ATMOSPHERES
A controlled atmosphere (CA) or modified atmosphere (MA) around the
produce is created by alterations in the concentrations of the respiratory
gases in the storage atmosphere; these alterations include elevation of
carbon dioxide (CO2) level, the reduction of oxygen (O2) tension, or both .
Whereas the term 'CA storage' generally implies precise control of O2 and
CO2 concentrations in the atmosphere, the term MA storage' is broader
and may indicate any synthetic atmosphere, arising intentionally or
unintentionally, in which the composition of its constituent gases cannot
be closely controlled.
Keeping fruits and vegetables in modified atmospheres is an old
technique. Wang (1990), in his review of physiological and biochemical
effects of controlled atmosphere on fruits and vegetables, mentions an
ancient Chinese poem that describes the fondness for lychees of an
empress in the 8th century. She demanded that freshly picked lychees be
transported, on horseback, from southern China to her palace, a distance
of about 1,000 km, and the fruit carriers discovered that lychees would
keep well if the fruits were sealed inside the hollow centers of bamboo
stems, along with some fresh leaves. Wang (1990) adds that while the
poem did not explain the reason for this, we know today that the
atmosphere produced within the bamboo stems by the continued
respiration of the fruits and the fresh leaves, was probably the reason for
the freshness of those lychees. During the last few decades,
understanding of the physiological and biochemical processes in the fruit
associated with alterations in the CO2 and O2 contents of the atmosphere
has considerably increased. Alterations in the levels of the atmospheric
gases were primarily aimed at suppressing the respiration and other
metabolic reactions of harvested fruits and vegetables, and so retarding
the ripening and senescence processes. During storage, many volatile
compounds are evolved from the stored fruits and vegetables, and these
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