In this study, composite films were prepared with collagen fiber (CF) and cellulose microfibrils (CMF) with different degrees of carboxylation coated with metal-polyphenol network (MPN) in order to evaluate the influence of the modification methods of CMF on the properties of the composite films. The results showed that compared to CF-CMF films, the oxidation resistance of CF-CMF-MPN films was increased by 51.49%, and the elongation at break and light resistance were also improved significantly. CMF modified with MPN and high content of carboxymethyl groups could minimize the impact of MPN on the mechanical strength of composite films. CMF modified with MPN and high content of carboxyethyl groups could increase the water vapor and oxygen barrier performance by 1.30 and 3.48 times, respectively. Scanning electron microscopy and infrared spectroscopic analysis showed that different modified CMFs and collagen fibers physically cross-linked and had good compatibility with each other. In conclusion, this study has provided a new means to improve the performance of composite films for better applications in the field of food packaging.

The metal-polyphenol network (MPN) formed by polyphenols and metal ions combines the specific functions of metal ions and high affinity of polyphenol structures to various surfaces synergistically. MPN can be adsorbed on various surfaces such as nanomaterials and biological interfaces, with more stable structure. In recent years, MPN has developed rapidly and been widely used in many fields. This article summarizes the assembly mechanism and components (mainly tannic acid and iron ion) of MPN, and briefly introduces readers to the common assembly methods of one-step blending deposition and layer-by-layer assembly, as well as the common characterization methods. Particularly, the antimicrobial activity, antioxidant effect, adsorptive property and pH response of MPN are discussed, with focus on its application in food field. Finally, this article gives an outlook on future trends in the development of MPN.