Development of Pork Ball Freshness Monitoring Labels Based on Carrageenan/Polyvinyl Alcohol Matrices and Anthocyanins from Three Petals: A Comparative Study

Anthocyanins were extracted from the petals of Loropetalum chinense var. rubrum, Petunia hybrida, and Rhododendron pulchrum Sweet, denoted as LA, PA and RA, respectively. Physicochemical properties of Loropetalum chinense var. rubrum (LA), Petunia hybrida (PA) and Rhododendron pulchrum Sweet (RA) were comparatively evaluated. Among them, RA exhibited the highest total anthocyanin content (49.41 ± 0.23a mg/g) along with the total phenolic amount (102.01 ± 0.15a mg/g). Immobilizing the obtained anthocyanin-rich extract in a carrageenan (CP) and polyvinyl alcohol (PVA) matrix and drying it at 30 °C and 50% relative humidity yielded a film intended for use as a smart packaging label to monitor Pork ball freshness. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR) analyses demonstrated excellent compatibility between anthocyanins and CP/PVA matrices, resulting in dense structures. The results of physicochemical and functional properties revealed that the prepared control films and anthocyanin films containing RA (CP-RA film) showed optimal performance, including superior visible light/oxygen barrier properties, tensile strength (45.49 MPa), elongation at break (26.47%), antioxidant capacity (42.75%), and pH-sensitivity. In addition, CP-RA film maintained its superior color stability over various temperature situations and displayed high sensitivity to changes in total volatile basic nitrogen (TVB-N) values.