Comparative effects of hydrophobic cellulose I and Ⅱ nanocrystals on the physicochemical properties of gelatin-based films for oil packaging.

Gelatin is a natural biopolymer for biodegradable food packaging films, but its inherent hydrophilicity and unsatisfactory mechanical properties limit its application in packaging lipid-rich foods and edible oils. This study aimed to investigate the effects of cellulose I/Ⅱ nanocrystals (CNC-I, CNC-Ⅱ) and their lauric acid-modified derivatives (LCNC-I, LCNC-Ⅱ) on the physicochemical properties of gelatin-based films. The results showed that both CNCs and LCNCs were uniformly dispersed in the gelatin matrix. Compared with CNCs, the addition of LCNCs further increased the microstructural compactness, structural disorder, and disulfide bond content of gelatin-based films, and improved their hydrophobicity, mechanical properties, as well as UV, oxygen, and water vapor barrier properties. These improvements were attributed to the plasticizing effect of LCNCs, together with strengthened physical entanglement and interfacial compatibility between LCNCs and the gelatin matrix. Notably, 10% LCNC-I showed superior performance in reducing film solubility (25.51 ± 1.15%), prolonging dissolution time (1085.71 ± 31.16 s), and enhancing hydrophobicity (105.0 ± 1.3°). By contrast, 10% LCNC-Ⅱ exhibited greater potential in enhancing tensile strength (51.29 ± 0.79 MPa) and improving oxygen barrier properties. In camellia oil packaging and storage tests, compared with commercial films, gelatin-based films incorporated with 10% LCNCs effectively retarded oil oxidation and rancidity during storage; especially, films incorporated with LCNC-Ⅱ exhibited a slightly better protective effect. These findings demonstrate that LCNCs can serve as promising reinforcements to optimize the overall performance of gelatin films for food packaging.