Effects of Chitosan-Based Ca2+ on Softening and Browning of Custard Apple Fruit During Postharvest Storage

Calcium treatment can reduce fruit softening and browning and enhance postharvest fruit quality. Chitosan (CS) had a certain viscosity. Therefore, in this study, calcium chloride (CaCl2) was used as a calcium source and CS was used as a carrier to study the interaction of Ca2+ and CS of the film coating through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). At the same time, the softening and browning process of custard apple fruit was investigated by single and composite coating with 1% CS and 2% CaCl2. The results showed that Ca2+ and CS produced physical and chemical cross-linking, and CS-CaCl2 could maintain total calcium content in coated custard apple. Compared with other treatments, CS-CaCl2 had the best postharvest effect on custard apple, which could reduce the weight loss rate of custard apple; maintain the firmness, color, moisture and cell wall material content of custard apple; and inhibit the rise and degradation of water-soluble pectin (WSP). At the same time, it could also improve the activity of superoxide dismutase (SOD) and inhibit malondialdehyde (MDA), polyphenol oxidase (PPO), and cellulase (CX) activity. This study provides a theoretical basis for improving the shelf life of custard apple.