Preparation and characterization of pH-indicator films based on chitosan and whey protein incorporated with beetroot extract and nisin for quality monitoring of cooked chicken breast meat

pH-responsive films offer a promising approach for freshness and quality monitoring. This study developed chitosan/whey protein films containing beetroot extract as a pH-responsive indicator and nisin at 0.5 or 1.0% (CWBN0.5 and CWBN1.0, respectively). Beetroot extract enhanced 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and imparted pH-responsive color changes, while nisin provided antibacterial activity against Staphylococcus aureus and Escherichia coli. These additives improved tensile strength and water vapor and oxygen barrier properties. During refrigerated storage, CWBN1.0 exhibited the lowest total volatile basic nitrogen (TVB-N) and total viable count (TVC), while beetroot-containing films showed lower thiobarbituric acid reactive substances (TBARS) levels. Film color changes coincided with changes in meat pH and TVB-N, supporting their potential for visual freshness monitoring. These findings suggest that combining beetroot extract and nisin could provide complementary preservation and freshness-indicating functions in cooked chicken packaging.