Effects of graft copolymer of chitosan and salicylic acid on reducing rot of postharvest fruit and retarding cell wall degradation in grapefruit during storage

This study was to evaluate the effect of graft copolymer (CTS-g-SA) of chitosan (CTS) and salicylic acid (SA) on the storability of grapefruit fruits during postharvest storage. Results indicate that the graft copolymer treatment significantly depressed green mold caused by Penicillium digitatum. The graft copolymer application kept fruit firmness without impairing the fruit quality. Moreover, the graft copolymer treatment inhibited the activity and gene expression of cell wall-modifying enzymes such as polygalacturonase, cellulase, pectin methylesterase, alpha-L-arabinofuranosidase, beta-galactosidase, and suppressed the modification of cell wall components including covalently bound polysaccharide (sodium carbonate soluble pectin, 24% KOH-soluble fraction), which were associated with fruit softening. These results suggested that graft copolymer application can be recognized as a postharvest technique to suppress rotting and delay softening through inhibiting solubilization of cell wall polysaccharides.