Preparation and characterization of pectin-carrageenan composite red spinach (Amaranthus dubius) extract-infused films.

This study presents the development and evaluation of a pH-sensitive smart food packaging film using anthocyanin extract derived from Red Spinach leaves. The natural anthocyanins, known for their vibrant colour and pH-responsive behaviour, were extracted through methanol-based cold extraction. These extracts were incorporated at varying concentrations (10%, 15%, and 20%) into a carrageenan/pectin (Cr/Pe) biopolymer matrix to form films via solution casting. Comprehensive physicochemical characterisation revealed that increasing anthocyanin content led to decreased moisture content, water solubility, and water vapour transmission rate (WVTR), thereby improving the films' barrier properties. Antioxidant assays (DPPH and ABTS) confirmed the strong radical scavenging activity of the films, particularly at higher extract concentrations. FTIR analysis indicated interactions between anthocyanins and the polymer matrix, while UV-Vis spectroscopy and pH buffer tests demonstrated vivid and reversible colour transitions in response to pH changes, confirming their suitability for smart packaging applications. Application testing on poultry meat showed distinct colour changes from pink to yellow as spoilage progressed, effectively signalling freshness loss due to rising pH levels. These results underscore the potential of Red Spinach extract incorporated films as sustainable, functional packaging materials for real-time freshness monitoring