Abstract: In order to investigate the influence of nanocrystal cellulose (NCC) addition to chitosan coating on its effect on the preservation of Shatangju mandarin (Citrus reticulata cv. Shatangju), the fruit were treated with chitosan solution (CS) and chitosan composite solutions containing 2% and 4% of NCC (CS-2% NCC and CS-4% NCC) in this study, separately. In addition, a prochloraz-treated group (PCZ group) and an untreated group (CK group) were set up. The mass loss rate, decay incidence, nutritional quality, malondialdehyde (MDA) content in the fruit peels and antioxidase activities in each group were determined regularly during storage, and the microscopic morphology of the peel surface was also observed. The results showed that the composite coating could not reduce fruit mass loss, but its inhibitory effect on the decay incidence was better than that of CS and PCZ. Compared with CK, the decay incidence of CS-4% NCC was reduced by 50% on day 24 of storage; meanwhile, the contents of titratable acid, soluble solid, total phenol and soluble protein were effectively maintained by chitosan coating. The content of peel MDA in CS-4% NCC was the lowest among all groups, and the activities of peroxidase (POD) and catalase (CAT) could be maintained at relatively high levels in this group during storage, which indicated that CS-4% NCC composite coating could significantly delay membrane lipid peroxidation, thus maintaining the anti-aging capacity of fruit. It was observed from the surface micromorphology of peels that micropores appeared on the coated fruit on the first day of storage, while addition of 4% NCC enhanced the structural stability of the coating, thereby helping in reducing the appearance of micropores. These results indicated that addition of NCC was able to stabilize the structure and improve the properties of CS coating, thus enhancing its preservation effect on fruits. The effect of 4% NCC composite coating on inhibiting fruit decay and maintaining fruit quality was similar to that of prochloraz treatment. Therefore, the composite coating could replace chemical preservatives for citrus fruits such as Shatangju mandarin.

Key words: chitosan; nanocrystal cellulose; coating; storage quality; Shatangju mandarin