Development and application of multifunctional films based on modified chitosan/gelatin polyelectrolyte complex for preservation and monitoring

Green and sustainable natural macromolecular-based multifunctional packaging has received widespread attention due to its excellent fresh-keeping effect and sensitive monitoring function. Herein, water-soluble modified chitosan (GCS) as the film substrate and emulsifier was synthesized first. Based on gelatin and GCS, a composite film (GF/GCS) and an emulsion film containing garlic essential oil (GF/GCSE2) were fabricated and compared. The interactions mainly included intermolecular hydrogen bonds and electrostatic interactions. The incorporation of GCS and the emulsion enhanced the hydrophobicity (water contact angle >100°) of films and also endowed the films with antioxidant activity and antibacterial activity (up to 100% for S. aureus and 97% for E. coli). Moreover, anthocyanins extracted from purple cabbage were added to the above two films as indicators to form pH-responsive smart labels GF/GCS/A and GF/GCSE/A. The gelatin/GCS polyelectrolyte complex improved the stability of anthocyanins in labels. Compared to commercial PE film, GF/GCS and GF/GCSE2 displayed better preservation effects on cherry tomatoes and fish. GF/GCSE2 exhibited the best preservation effect on cherry tomatoes, significantly reducing the decrease in total phenolic content and titratable acids. The integrated packaging composed of GF/GCS and GF/GCS/A could effectively prevent fish spoilage (TVB-N<15 mg/100 g) and sensitively reflected the freshness of fish during storage at 4 °C.