Enhanced Storage Resistance of Mulberries Using Laminated Cellulose Nanocrystals/Chitosan Composite Coatings

Abstract

Fresh mulberry is a soft and juicy fruit with no protective layer on the skin, limiting its storage and transportation. Nanocellulose (NCC) and chitosan (CS) films have extensive potential in packaging due to their high–gas barrier, excellent mechanical, and antibacterial properties. Therefore, this study aimed to improve the storage resistance of fresh mulberries using laminated cellulose nanocrystal/CS (NCC/CS) composite coatings. The relationships between film microstructure, gas barrier characteristics, and mulberry storage properties were investigated. The results showed that the prepared NCC had a crystallinity of 80.40% with the length of 382.53 ± 42.40 nm and the diameter of 10.97 ± 4.71 nm. It was capable of forming a uniform film with an oxygen transmittance rate of 23.97 × 10³ cm³/(cm² day) and a solubility rate of 0.0025 g/min. The laminated NCC/CS composites had a denser structure, a lower oxygen transmittance rate of 0.62 × 10³ cm³/(cm² day), and antibacterial properties, as indicated by an inhibition circle measuring 5.3–6.2 mm in diameter. During storage, NCC/CS-coated mulberries displayed a slowly reducing sensory quality, lower mass loss rate, and lower rotting rate. After 10 days, compared with the uncoated mulberry, the soluble solid content in NCC/CS-coated mulberries decreased from 10.9 to 8.73%, soluble glucose content increased from 5.24 to 6.2%, and malondialdehyde content increased from 20.43 to 37.95%. The coating provided mechanical protection and offered superior oxygen barrier properties and a denser microstructure, leading to a weaker respiratory function and better mulberry storage. The findings of this study provided a novel approach for the practical application of NCC materials.