pH-sensitive films containing anthocyanins extracted from black bean seed coat and red cabbage

The aim of this study was to develop pH-sensitive films based on corn starch and anthocyanins extracted from black bean seed coat and red cabbage. The pH-sensitive films were developed from solvent casting of polymer solutions containing corn starch, glycerol, and anthocyanin extract (from red cabbage or black bean) prepared at pH 5. The color of films changed from pink to purple and blue, as a function of the pH. The pH-sensitive films were evaluated by their morphological, chemical, physical, mechanical and thermal properties. In addition, the stability was evaluated during 28 days of storage (presence and absence of light; with and without cooling). The pH-sensitive films with red cabbage anthocyanins showed a higher stability than that with black bean anthocyanins when stored at room temperature and exposed to light. Both pH-sensitive films exhibited greater color stability when stored under refrigeration as compared to storage at room temperature.