Development of pH-Sensitive Intelligent Packaging Films Based on Polyvinyl Alcohol Incorporated With Lycium ruthenicum Anthocyanin and Curcumin for Real-Time Monitoring of Mutton Freshness

A multifunctional intelligent packaging film was fabricated by co-incorporating Lycium ruthenicum anthocyanins (LRAs) and curcumin (CUR) into a polyvinyl alcohol (PVA) matrix. Microstructural and spectroscopic analyses supported the successful incorporation of both pigments and their intermolecular interactions with the PVA matrix. Notably, the physicochemical and functional properties of the composite films varied with the LRA/CUR ratio. Specifically, the CUR-dominant formulation (1:2) exhibited the highest elongation at break (86.13%) and antioxidant activity (DPPH scavenging rate of 63%) among the binary formulations, together with stronger antibacterial activity. Conversely, the LRA-dominant film (2:1) exhibited greater color stability and the strongest ammonia response (maximum Δ E = 35.02). When applied to chilled mutton stored at 4°C for 8 days, the intelligent films displayed progressive color transitions from yellow-orange to reddish-orange as spoilage progressed. These chromatic variations were accompanied by increases in pH (from 6.42 to 7.41) and total volatile basic nitrogen (TVB-N) content (from 9.29 to 39.41 mg/100 g). Overall, the LRA/CUR-PVA films combined freshness indication with active preservation, demonstrating their potential for intelligent chilled-meat packaging.