Preparation and Performance Characterization of a Composite Film Based on Corn Starch, &kappa;-Carrageenan, and Ethanol Extract of Onion Skin
Using corn starch (CS) and &kappa;-carrageenan(&kappa;C) as the raw material and active composite, respectively, films containing different concentrations of ethanol extract of onion skin were prepared. The effects of different concentrations of ethanol extract of onion skin (EEOS) on the physicochemical properties, as well as the antioxidant and antibacterial properties, of CS/&kappa;C films were also discussed. The addition of ethanol extract of onion skin inhibited the recrystallization of starch molecules in the composite films. It affected the microstructure of the composite films. The color of the composite films was deepened, the brightness was reduced, and the opacity was increased. Water vapor permeability increased, tensile strength decreased, and elongation at the break increased. The glass-transition temperature decreased. The clearance of DPPH radicals and ABTS cation radicals increased. Moreover, when the concentration of EEOS was 3%, the antioxidant effect of the films on oil was greatly improved and could effectively inhibit Staphylococcus aureus and Escherichia coli. The above results showed that adding ethanol extract of onion skin improved the physicochemical properties and biological activities of the CS/&kappa;C composite films, so CS/&kappa;C/EEOS composite films can be used as an active packaging material to extend food shelf-life. These results can provide a theoretical basis for the production and application of corn starch/&kappa;-carrageenan/ethanol extract of onion skin composite films.