Studies on post-harvest treatments of chitosan and selenium on membrane lipids and antioxidant status in guava (Psidium guajava L.) fruit
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Date
2017
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CCSHAU
Abstract
During present investigations, guava fruits of variety Hisar Surkha (shelf-life 2-3 days) were
harvested at immature green, mature green, ripe and over-ripe stages of ripening during summer and
winter seasons. The lipoxygenase activity increased progressively throughout ripening in both the
seasons but fruits harvested during winter season showed lower activity as compared tofruits of
summer season. The amount of total lipids, polar lipids, non-polar lipids, phospholipids and glycolipids
increased upto ripe satge and declined thereafter at the over-ripe stage in both the seasons. The ratio of
unsaturated to saturated fatty acids also declined during ripening but the decline waslower in winter
fruits. Pre-treatment of fruits with chitosan and seleniumalone and in combination significantly delayed
decline in physiological loss in weight, total soluble solids and more retention of firmness, acidity,
sugars, phenolics, flavonoids and total antioxidant acivity during storage. However, the higher doses
(0.04-0.05 ppm) of selenium showed negative effect on quality of guava fruits. The oxidative stress
indicated by superoxide radicals, hydrogen peroxide content, melondialdehyde content and
lipoxygenase activity, increased significantly during storage at both room temperature (20±2 0C) and
low temperature (5±2 0C) but fruit stored at low temperature showed lower oxidative stress. The
activities of reactive oxygen species scavenging enzymes viz.superoxide dismutase, catalase,
glutathione reductase, glutathione peroxidaseand glucose 6-phosphate dehydrogenase decreased
continuously while the activities of ascorbate peroxidase, peroxidase and polyphenol oxidase increased
initially and invariably low at the later stages during storage at both temperatures. Antioxidative
metabolites, ascorbic acid increased initially and declined at later stages while glutathione and β-
carotene content decreased continuously throughout the storage period. However,decrease was less in
all treated fruits except higher Se concentration (0.05 ppm) and storage at low temperature. During
storage all classes of lipids decreased continuously and the ratio of unsaturated to saturated fatty acid
also decreased but the fruits treated with chitosan along with Se stored at low temperatue retained high
amount of all lipid classes and fatty acids.The treatment of chitosan (1.5%) and Se (0.02 ppm) was
most effective at low temperature than at room temperature in delaying the lipid peroxidation and
oxidative stress and maintaining the textural quality and fluidity of the membrane.
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