Development of a multifunctional starch/cellulose-based film with superior mechanical strength, antibacterial activity and visual food freshness indication

Real-time monitoring of food freshness is an efficient strategy to ensure food safety. In this work, a biomass-derived antibacterial and high-strength film featuring an intelligent freshness indication was developed, utilizing neutral red-bromothymol blue (NR-BTB) as a couple indicator, while high amylose corn starch-cinnamaldehyde (HACS-CIN) and bacterial cellulose nanofibers (BCNFs) as the film matrix. The FT-IR and encapsulation efficiency results demonstrated that the CIN was successfully encapsulated within the helical structure of the HACS via intermolecular interactions. The HACS-CIN/BCNFs films exhibit strong antibacterial activity against E. coli and S. aureus . After the incorporation of NR-BTB, the composite films exhibited a high mechanical strength of 27.05 ± 2.57   MPa and a responsive color change within a pH of 3 11. The multifunctional film maintained satisfactory color stability at both 4°C and 25°C at different humidity over 14 days. The cytotoxicity test indicated the composite films have good biocompatibility. As the freshness of the shrimp declined and the levels of TVB-N increased during storage, the color of the multifunctional film significantly changed from reddish-brown to yellowish-brown. This composite film exhibited sensitive pH responsiveness and no leakage in fat simulant. The results indicated that the composite film has the potential to be a real-time food freshness indicator.