Preparation, characterization, and application of pH-responsive biodegradable intelligent indicator film based on rose anthocyanins

An intelligent pH-responsive indicator film (CA/CMC/RA) was fabricated by blending carrageenan (CA), carboxymethylcellulose (CMC), and rose anthocyanin (RA). Fourier transform infrared spectroscopy revealed the formation of hydrogen bonds between CA/CMC and RA. X-ray diffraction analysis demonstrated that the addition of RA enhanced the crystallinity of CA/CMC films. The incorporation of RA altered the microstructure of CA/CMC composite films, resulting in a roughened surface. RA improved the a*, b*, thickness, opacity, and water vapor permeability of CA/CMC/RA films. Moreover, the addition of RA increased the elongation at break, while decreasing the tensile strength. RA significantly increased the antioxidant capacity of CA/CMC films. Furthermore, CA/CMC/RA films exhibited pH-responsiveness, showcasing distinct color changes in different buffer solutions. In the application test, the CA/CMC/RA indicator film was used as a label to monitor the freshness of the ribbon fish stored at 4 °C. The results indicated that the film's color changed from pink to yellow upon spoilage. The observations were consistent with the TVB-N value, which exceeded the set limit (30mg/100g). Hence, the novel indicator film can serve as a food freshness indicator material