A double-layer film based on the strategy of tannic acid-anthocyanin co-pigmentation and tannic-crosslinked-gelatin/-reduced Ag nanoparticles for beef preservation and monitoring.

A double-layer film was developed with tannic acid (TA) co-pigmented purple potato anthocyanin extract (PAE)-agar as the inner layer, and K-carrageenan-oregano essential oil Pickering emulsion (OPE)/silver nanoparticles (TA-AgNPs) as the outer layer. Molecular docking and FT-IR results elucidated that intermolecular hydrogen bond was the main interaction between components in the agar-carrageenan matrix, with TA and PAE contributing to intensified anthocyanin color through π-π stacking. The incorporation of OPE/TA-AgNPs enhanced the film's hydrophobicity (WCA > 100°) and UV-vis barrier (close to 0% at 200-320 nm, effectively impeding UVA, UVB, and UVC) properties and exhibited outstanding antioxidant (DPPH scavenging rate > 88%) and antimicrobial activities. This film showed a significant color change in the pH range of 2-12 (from pink to yellow) and a considerable sensitivity to volatile amines within 2 min. The films effectively alleviated beef spoilage (extending the shelf life of beef for 1d) and reflected the freshness of beef during storage. Additionally, the digital color information of the film was obtained by a smartphone combined with RGB values analysis to quantify the freshness of beef rapidly. Therefore, this study expands the application of food packaging films with freshness preservation and monitoring in the field of animal-derived food.

The synergistic effect of polyphenols and polypeptides for plant-based bioplastic film - Enhanced UV resistance, antioxidant and antibacterial performance.

The exceptional biodegradability and active biological functions of bio-based packaging materials have attracted increasing interest. In this study, a bioplastic film was developed by introducing simultaneously polyphenols (tea polyphenols, TPs) and peptides (nisin) into a soy protein isolate/sodium alginate (SPI/SA) based film-forming matrix. The research results revealed that the dynamic coordinated interaction between TPs and nisin enhanced mechanical properties, UV-resistance, and thermal stability of bioplastic films. Furthermore, the bioplastic film exhibited antibacterial activity and antioxidant properties. Significantly, biofilm growth of Staphylococcus aureus treated with TPs-5/Nisin-5 bioplastic film was inhibited by 91.12% compared to the blank group. The shelf life of beef with TPs-5/Nisin-5 bioplastic film was prolonged by 2 days because of the synergistic effect of TPs and nisin. Additionally, the bioplastic film biodegraded in the natural environment about 21 days. This environmentally friendly regeneration strategy and the integration of advantageous functions provided ideas for the development of active food packaging.