Green Smart Packaging Film Based on Kappa-Carrageenan/Poly(Vinyl Alcohol) Enriched with Mexican Petunia Anthocyanins for Visual Detection of Food Freshness

Abstract

This research presents a novel approach for the development of environmentally friendly and pH-sensitive films composed of kappa-carrageenan and poly(vinyl alcohol), designed to facilitate real-time monitoring of food freshness. Sol–gel cross-linked films, enriched with natural anthocyanins extracted from Mexican petunia flowers, were prepared using an aqueous solution casting method. The formation of siloxane cross-linking and the successful incorporation of anthocyanins were confirmed by ATR-FTIR spectroscopy. Scanning electron microscopy revealed homogeneous and uniform film morphology. The incorporation of the anthocyanin extract enhanced the water vapor barrier performance and mechanical properties of the films, while imparting notable antioxidant activity, UV-blocking, and pH responsiveness. The environmental sustainability of the films was verified through a soil burial degradation test. Notably, the films exhibited distinct color transitions, shifting from pink to light-brown, brownish-green, and yellow, when subjected to pH changes between 1 and 12. When employed to monitor the spoilage of fresh shrimp, the pH-sensitive films revealed clear visual changes coinciding with spoilage, along with a corresponding rise in total volatile basic nitrogen levels. Overall, this study demonstrates that the integration of anthocyanins extracted from Mexican petunia flowers significantly enhances the functional properties of kappa-carrageenan/poly(vinyl alcohol) films. The resulting materials exhibit desirable characteristics, including pH responsiveness, making them well-suited for use in food packaging. Consequently, this green functional material holds considerable promise as smart packaging films for the real-time monitoring of food freshness.