Physicochemical, Antioxidant, In Vitro Release, and Heat Sealing Properties of Fish Gelatin Films Incorporated with β-Cyclodextrin/Curcumin Complexes for Apple Juice Preservation

The antioxidant activity of gelatin film is poor. Curcumin is a natural antioxidant, but its main disadvantage is low aqueous solubility. In this study, curcumin was encapsulated by beta-cyclodextrin to prepare beta CD/CUR complex. Gelatin films incorporated with beta CD/CUR complexes (GL-beta CD-CUR films) were fabricated. The effects of curcumin content on their properties were investigated. Results showed that the water solubility of curcumin was improved in beta CD/CUR complex. The beta CD/CUR complex containing 2.5 mg curcumin had smaller size and more homogeneous distribution. The thicknesses of all films were about 87 mu m and there were no significant differences (p > 0.05). The optimal tensile strength (TS) and elongation at break (EAB) of GL-beta CD-CUR films were observed at the curcumin content of 2.5 mg. With the increase of curcumin concentration, water vapor permeability (WVP) of gelatin-based films decreased from 2.88 to 2.38 x 10(-10) g m(-1) Pa-1 s(-1) and water content (WC) decreased from 34.64 to 24.72%, but water solubility (WS) increased from 21.22 to 59.75%. GL-beta CD-CUR films exhibited lower light transmission in UV light compared with GL-beta CD film. SEM provided that there was a good compatibility between gelatin molecules and beta CD/CUR complexes. FTIR proved that no functional groups appeared or disappeared. A significant increase in antioxidant activity and the stability of this activity along with a lower release rate of curcumin in food simulant were observed in gelatin films incorporated with beta CD/CUR complexes. The heat sealing property of GL-beta CD-CUR films containing 1 or 2.5 mg curcumin was better than that of film containing 5 mg curcumin. The L values of red Fuji (Malus pumila mill) apple juice packed by GL-beta CD-CUR films reduced slowly. The slowest decline in total polyphenol content was found in GL-beta CD-2.5CUR group. Our results indicated that the incorporation of beta CD/CUR complex significantly enhanced the antioxidant activity of gelatin film, and the GL-beta CD-CUR film can be used in apple juice preservation.