Preparation of Tea Polyphenol‐Enhanced Whey Protein Isolate/Sodium Carboxymethyl Cellulose Composite Films and Their Antioxidant and Antibacterial Properties

ABSTRACT Biodegradable composite films are prepared using whey protein isolate (WPI) and sodium carboxymethyl cellulose (CMC‐Na) as matrices, with tea polyphenols (TP) incorporated into the composite matrix. The incorporation of TP significantly enhances the ultraviolet (UV) barrier performance, antioxidant activity, and antibacterial activity against Escherichia coli . The 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activity (RSA) reaches 23.37%, representing an approximately 170% increase compared with the control film, while the inhibition zone diameter reaches 13 mm. The mechanical properties generally decrease and then increase with increasing TP content, whereas the water vapor transmission rate (WVTR) and oxygen permeability (OP) exhibit non‐monotonic variations with TP incorporation. Among all samples, the WPI/CMC‐Na/TP‐6 film containing 0.6 wt% TP exhibits a compact microstructure, comparable thermal degradation behavior, and balanced barrier performance. These results demonstrate that TP effectively improves the structural and functional properties of WPI/CMC‐Na composite films, indicating promising potential for active food packaging applications.