Preparation, physicochemical and application evaluation of raspberry anthocyanin and curcumin based on chitosan/starch/gelatin film

Raspberry anthocyanin (RA) from Rubus idaeus L. (Rosaceae) and curcumin (Cur) from Curcuma longa L. (Zin-giberaceae) can effectively improve the physicochemical properties of composite films, and as bioactive pigment components, they can impart pH-responsive properties to the film. In this study, RA and Cur were added to chitosan/starch/gelatin composite film (CSG) to prepare CSG-RA, CSG-Cur, CSG-RA/Cur(82) and CSG-RA/Cur(73) color films by solution casting method. The color films could change color under different pH conditions and had higher antioxidant activities using ABTS (2,2 '-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)) assay. The results from fourier transform infrared spectroscopy and scanning electron microscopy showed that RA and Cur were well dispersed in the CSG matrix and improved the structure of the composite films. The hydrophobic Cur increased the tensile strength from 6 Mpa (CSG) to 14 Mpa (CSG-Cur), but reduced the elongation at break from 55 % (CSG) to 40 % (CSG-Cur). These color films had a good fresh-keeping effect and freshness monitoring, in particular, CSG-RA/Cur(73), had the better opacity, water solubility, thickness, moisture content and water vapor permeability than the other films. Briefly, binary pigment films had the potential to become a pH-sensitive indicator/packing film.

Automated summary

Raspberry anthocyanin and curcumin can effectively improve the physicochemical properties of composite films and impart pH-responsive properties. The color films can change color under different pH conditions and have higher antioxidant activities. Fourier transform infrared spectroscopy and scanning electron microscopy results show that the pigments are well dispersed in the film matrix and improve the film structure.