Improving preservation effects of Taiwan jujube fruits by using chitosan coating combined with ascorbic acid during postharvest period

In order to demonstrate the fact that ascorbic acid (AsA) increased anti-oxidation and chitosan prevented dehydration and microbial attack, this paper systematically investigate effects of chitosan coating, AsA, and their combinational treatment on preservation of harvested Taiwan jujube fruits during storage. In treatment of 30.0 mmol/L AsA, 8 g/L chitosan, 30.0 mmol/L AsA combined with 8 g/L chitosan, and dipped in deionized water (as control), respectively, all samples were stored in darkness at (25±1)°C and 90%-95% relative humidity. Relative physiological parameters were measured and cells structures were observed by scanning electron microscope in pericarp and pulp tissue. Results showed that, compared to the control, AsA or chitosan alone improved storability of harvested fruits and their combinational treatment showed a better effect. Fruits water loss and relative leakage rate of pericarp were markedly reduced (P<0.05), and an increase in pericarp chlorophyll degradation and activities of pectin methylesterases (PME) and polygalacturonases (PG) in pulp was inhibited, and degradation rate of protopectin to soluble pectin was markedly reduced (P<0.05). Thus, high degree of fruits firmness and integral cell structure was maintained. A decrease in activities of superoxide dismutase (SOD) and catalase (CAT) was alleviated, membrane oxidation rate was reduced, and thus contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) were markedly decreased (P<0.05). An increase in contents of soluble sugars, total soluble solids, titratable acidity, glutathione and AsA was achieved. It was indicated that chitosan coupled with AsA treatment play active roles in enhancing anti-oxidation, decreasing oxidation injury, fruits water loss, and chlorophyll degradation, alleviating pericarp browning, delaying fruits softening, maintaining cell integrity, and reducing decay rate, thus realizing improved preservation effects of harvested Taiwan jujube during storage.