Properties of Gelatin-based Films Incorporated with Anthocyanins and Curcuminoids and Stability of Antioxidant Activity during In Vitro Digestion

In this study, gelatin-based films incorporated with two plant pigments; butterfly pea flower anthocyanins (BPA) and turmeric rhizome curcuminoids (TRC) were prepared. Their physical and antioxidant properties were investigated. The results showed that addition of BPA and TRC at different concentrations (10%, 20%, and 30% of gelatin weight) significantly affected the visible color and color values (L*, a*, b*, hue and chroma) of the obtained films. With increasing pigment concentrations, lower % light transmittance was observed (p<0.05). The improved light barrier property corresponded with the increased opacity of the two films (p<0.05). Compared with the control films, the addition of either BPA or TRC slightly increased thickness of films  (p<0.05). The moisture content of films increased with increasing BPA concentration but decreased with increasing TRC concentration (p<0.05). However, water solubility was not significantly different among films with varying concentrations of BPA or TRC (p>0.05). Total anthocyanin content (TAC), total curcuminoid content (TCC), total phenol content, and antioxidant activities by FRAP and DPPH increased with increasing pigment concentration in films (p<0.05). Based on in vitro digestion, the film forming solution containing 30% (w/w) plant pigment significantly improved the stability of pigment compounds, TPC, and antioxidant activities during the intestinal phase. Compared to the pigment extract alone, film forming solution containing gelatin and glycerol showed protecting effects against biological conditions during intestinal digestion of the two pigments, BPA and TRC, and therefore, offered greater stability of antioxidant activity (p<0.05).