Intelligent gelatin/oxidized chitin nanocrystals nanocomposite films containing black rice bran anthocyanins for fish freshness monitorings

A green nanocomposite film with pH-sensitivity and antioxidant activity based on oxidized chitin nanocrystals (O-ChNCs)/gelatin incorporating black rice bran anthocyanins (BACNs) was prepared in this study. Fourier transform infrared spectrum showed that BACNs were successfully immobilized into the O-ChNCs/gelatin matrix through non-covalent bonds. Scanning electron microscopy and atomic force microscope showed that BACNs was uniformly distributed in the O-ChNCs/gelatin matrix. Although the incorporation of BACNs decreased the mechanical properties of the films, it endowed the films with excellent UV–vis light barrier and antioxidant character. Moreover, the O-ChNCs/gelatin/BACNs films were pH-sensitive and showed remarkable color changes in different buffer solutions, which could be used to monitor the freshness of shrimp and hairtail by visible color changes. The colorimetric films with lower content of BACNs were found more sensitive toward basic volatile amines emitted during storage. Therefore, the developed O-ChNCs/gelatin/BACNs films may have a great potential in the freshness monitoring of high protein foods.