Metal polyphenol network-modified chitin nanocrystals reinforce versatile biomass films: Active packaging, intelligent visualization and controlled photothermal sterilization

•First use of MPN interfacial engineering to confer multifunctionality for CNC.•CNC@MPN/SA-F is an excellent active packaging.•CNC@MPN/SA-F is an intelligent platform for real-time visualization of food quality.•Visible light photothermal sterilizability of CNC@MPN/SA-F for food outer packages. The development of food packaging based on natural biomass is a growing focus for researchers and consumers. Beyond the traditional role of food preservation, there is an urgent demand for active packaging and intelligent sensory capabilities. In response, we have developed an integrated system using all-natural materials. Centered on the concept of nanofilled reinforced biomass films, the system integrates active molecules (tannic acid, TA) and an intelligent sensing system (metal polyphenol network, MPN) onto chitin nanocrystals (CNC). This innovation addresses the challenge of compositing CNC with commonly used anionic polysaccharide matrices, represented by sodium alginate (SA). The resulting composite films exhibit unprecedented breakthroughs, including a 30.6% increase in tensile strength and a 136.3% increase in elongation at break, demonstrating improved mechanical properties. In addition, the films possess active packaging features such as antimicrobial, antioxidant, water-blocking, and biosafety properties. Notably, MPN has been integrated into food packaging and is being developed as a multifunctional platform for real-time visual monitoring of food quality and controllable visible light photothermal sterilization for the first time. This platform not only meets the criteria for active packaging and intelligent packaging but also demonstrates that the scientific and rational regulation of the properties of various materials and their combinations, using food-grade raw materials and production technologies, can significantly enhance material performance. This work offers generic reference value for future advances in material performance in food packaging.