Preparation and Characterization of Colorimetric Indicator Films Based on Chitosan/Polyvinyl Alcohol and Anthocyanins from Agri-Food Wastes

This work aimed to compare the potential application of anthocyanins extracted from jabuticaba fruit (Plinia cauliflora) and purple sweet potato (Ipomoea Batatas L.) peels as potential raw materials to manufacture colorimetric indicator films. The effect of anthocyanin source on morphology, thickness, moisture content, hydrophobicity, solubility in water, chemical structure, thermal properties, color, and opacity of films was analyzed. Furthermore, color change of films when exposed to controlled visible light and their application to monitoring meat freshness at three temperatures (- 20, 4, and 20 degrees C) was studied. Anthocyanins from both agri-food wastes increased the molecular spacing in the polymer chains, increasing thickness values and decreasing the thermal stability of the films. However, this effect was more evident when anthocyanins from purple sweet potato peels were used. The other physicochemical properties of colorimetric films were not altered with the presence of anthocyanins. Both colorimetric indicator films showed visible changes from red color to blue color when used to monitor meat freshness at the proposed storage temperatures. Based on physicochemical and colorimetric results, jabuticaba peel is an interesting agri-food waste to manufacture colorimetric indicator films for the food packaging sector.