Protein-polyphenol conjugates and complexes for multifunctional food packaging

Proteins are increasingly recognized as promising alternatives to conventional synthetic polymers in food packaging owing to their sustainability, biodegradability, renewability, and favorable techno-functional properties. However, biodegradable materials made solely from proteins often suffer from low mechanical strength and barrier efficiency, high water sensitivity, and limited biofunctional properties, restricting their practical applications in food packaging. Protein-polyphenol interactions have emerged as an innovative strategy to enhance the performance of protein-based biodegradable materials. Polyphenols, naturally occurring plant compounds known for their antioxidant, antimicrobial, and crosslinking abilities, can interact with proteins through non-covalent complexation and covalent conjugation. These interactions improve the structural, physicochemical, and functional characteristics of protein-based materials, rendering them suitable for multifunctional food packaging systems. This review provides a comprehensive overview of the fundamental principles governing protein-polyphenol complexation and conjugation, with an emphasis on the underlying chemical mechanisms, structural modifications, and analytical characterization methods. It discusses how these interactions enhance techno-functional properties and film performance, including improved mechanical strength, thermal stability, barrier properties, and antimicrobial and antioxidant activities. Furthermore, the review highlights the potential of protein-polyphenol conjugates and complexes in developing multifunctional packaging materials designed to extend shelf life and preserve food quality, while addressing current challenges and future research directions. The combination of protein renewability with polyphenol bioactivity offers a sustainable and eco-friendly pathway toward next-generation packaging materials that reduce plastic waste and enhance food shelf-life and safety.