Improved mechanical, thermal and barrier properties of sericin/gelatin/carboxymethyl chitosan based films by laccase for packaging application in fruits and food cooking

Sericin films possess brittleness, poor tensile strength, and water-solubility, thus limiting its application in food packaging. The laccase treatment could enhance the properties of sericin/gelatin/carboxymethyl chitosan-based films, especially when main mass ratio of raw materials, i.e., sericin: gelatin: carboxymethyl chitosan was 1.67: 1.67: 4.17 with laccase being 0.15 U/mL (crosslinking for 12 h under 25 °C). This enhancement included increasing tensile strength by 80.93 %, promoting high heat sealing strength by 292.89 %, reducing thermal shrinkage by 73.66 %, lowering oxygen transmittance by 91.54 % as well as water vapor permeability by 43.98 %, along with outstanding antioxidant capacity. This is owing to that laccase can catalyze tyrosine groups of sericin, induce interactions among components and contribute to a denser structure with compact network (high viscosity, high storage modulus, low particle size and uniform micromorphology), leading to improvements in mechanical, thermal and barrier performances. The optimal films effectively delayed weight loss, and pH &firmness variation while maintaining freshness of cherry tomatoes, and promoted the quality of millet porridge after cooking. This study provides a theoretical basis for the application of sericin-based systems in food protection and offers new insights into the development of eco-friendly, biodegradable materials for broad application prospects in food packaging.