Anthocyanin-Functionalized Hydrophobic Cellulose Composite Films as Sensitive Colorimetric Indicators to Monitor Beef Freshness.

In recent years, emerging biodegradable food-packaging materials based on nanocellulose with excellent comprehensive performance have become a promising, environmentally friendly raw material, which can be used as an ideal substrate for degradable composite films. However, the poor water resistance and flexibility of nanocellulose composite films limit their practical applications. Herein, nanocellulose films composed of chitin nanocrystals (ChNCs) and anthocyanin (BA) were utilized to obtain water-resistant, antibacterial, and flexible nanocellulose composite films. Owing to the nonpolar aromatic rings in the structure of BA, the water contact angle (WCAs) test indicated that the introduction of BA effectively improved the hydrophobicity of the nanocellulose composite film (WCA, up to 95°), and nanocellulose composite films possessed enhanced antibacterial/antioxidant properties (DPPH scavenging rate, 79.15%; 66.62% for E. coli and 78.07% for S. aureus). Importantly, the introduction of BA effectively enables the film to indicate the freshness of a nanocellulose food wrap, considering its pH/NH3-responsive properties. In addition, the weight loss rate of CCBA-9 film reached 90.21% after 13 days, demonstrating good biodegradability. Therefore, by innovatively introducing the synergistic system of BA and ChNCs, the material breaks through the technical bottleneck of traditional polymer packaging materials and provides a disruptive solution for the development of the next generation of environmentally friendly smart food packaging materials.