The combined effect of ascorbic acid and chitosan coating on postharvest quality and cell wall metabolism of papaya fruits

Papaya fruit easily decays and prematurely senescence after harvest. Studies have shown that adding ascorbic acid to chitosan can improve postharvest quality and extend the shelf life of coated fruits. Therefore, the effect of 1.5% (w/v) ascorbic acid (AsA), 1.0% (w/v) chitosan (CTS), and 1.5% (w/v) ascorbic acid + 1.0% (w/v) chitosan (AsA + CTS) treatment on the storage quality of papaya fruits was studied. The results showed that AsA + CTS treatment reduced the weight loss, malondialdehyde, and hydrogen peroxide content of papaya fruit. AsA + CTS treatment improved the antioxidant capacity of papaya fruits by increasing the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase), soluble sugar and total phenol content, as well as by maintaining color and delaying senescence of fruits. AsA + CTS treatment also inhibited fruit softening by reducing cell-wall- degrading enzymes activities and by encoding gene transcript levels for cellulase, polygalacturonase, pectin methylesterase, and β-galactosidase. In summary, AsA + CTS treatment was an effective technique for maintaining the postharvest storage quality of papaya fruits.