Postharvest treatments to reduce chilling injury symptoms in stored ...

SA is a natural signaling molecule, which mediates defense against many
pathogens and also plays an essential role in thermogenesis. In mammals prior treatment
with SA induces heat shock protein in response to heat stress (Jurivich et al., 1992). JA
and MJ are called growth regulators and MJ is more volatile than JA. It is one of the main
odor compounds of jasmine. MJ is also a flavor ingredient of semi-black and black tea.
Plants that are attacked by insects or mechanically damaged produce higher levels of JA
and MJ. Wounded parts release an 18 amino acid polypeptide, systemin, which, activates
cell membrane lipase enzyme which ultimately releases linolenic acid, a main precursor
of JA and MJ. As these compounds are volatile in nature as such they provide quick
signals to neighboring cells and promote them to produce defensive chemicals before they
are attacked. When strawberries and papaya treated with MJ (10 -5 M), and stored in MA
packaging at 10 ºC, loss of firmness, inhibition of fungal decay and reduction in CI has
been noted ( González-Aguilar et al, 2003). Wang and Buta (1994) reported delay of CI
symptoms for 2-4 days in zucchini squash fruits treated with MJ prior to cold storage. MJ
also effectively reduced CI in mangoes (González-Aguilar et al., 2000a), grapefruit, bell
pepper and avocado (Meir et al., 1996). MJ either applied in gas or vapor form has similar
effect on CI incidence.
(b) Diphenylamine
Postharvest application of Diphenylamine (DPA) is commercially used to control
scald production in fruits. During scald production, hypodermic cells (the layer of loose
connective tissue immediately deep to the dermis of the skin) are affected at the depth of
40-150 µm from the surface. It is an antioxidant for carotene and other unsaturated
substances. Carotene synthesis by microorganisms is also decreased by DPA-treatments,
which inhibit the dehydrogenation of saturated polyenes to carotenoid. It has variable
effect on ester production in stored apples.
Apple and pear surfaces have a-farnesene hydrocarbon along with its antioxi-
dation products which are mainly responsible for black scalding of fruits after cold
storage (Anet, 1972). Anet (1972) reported the oxidation of a-farnesene and identified
two conjugated trienes (CTs) from the skin of stored apples. These CTs are toxic to the
fruit tissues as they initiate free-radical mediated chain reaction and decomposition to
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