Abstract:The single-layer chitosan film and the Na-carboxymethyl cellulose/chitosan double-layer film were prepared by casting method, and the mechanical properties, microstructure and water vapor transmission rate were investigated. Two Citrus varieties of Chunxiang and lemon were used as test materials. The effects on the postharvest quality of two Citrus fruits (Chunxiang, lemon) during shelf life by chitosan monolayer coating and Na-carboxymethyl cellulose/chitosan self-assembled coating were studied. Results showed that the water vapor permeability of the composite film significant (p<0.05）higher than single-layer film and it was 1.74 times that of the chitosan film. What’s more, it could maintain good mechanical properties and microstructure. Applied to the Citrus preservation, the film could improve the lightness of Citrus, inhibit the oxidation of ascorbic acid (Vc) and reduce the decline of firmness. By reducing the number of stomata on the surface of Citrus fruit, coating can effectively reduce weightlessness rate which controlled in 7.5% during storage and delay the decline on titratable acid content of Citrus fruit. Compared with single-layer coating, Na-carboxymethyl cellulose/chitosan self-assembled coating can significantly (p<0.05) improve the postharvest quality of Chunxiang and lemon, maintain high firmness and Vc content, and prolong the storage period. After 20 d of storage, the firmness of Chunxiang and lemon were 1.15 and 1.23 times that of the control group, respectively. This work confirmed that the polysaccharide film formed by electrostatic adsorption and self-assembly had the potential to maintain postharvest quality of Citrus fruits and provided reference for the study on the preservation of biological coating film on different Citrus varieties.
