Smart gelatin films prepared using red cabbage (Brassica oleracea L.) extracts as solvent

Abstract

This work studied the preparation of smart edible films based on gelatin and anthocyanins. Films were prepared by casting using aqueous or alcoholic extracts of red cabbage (Brassica oleracea L.) as solvent. The addition of these extracts to formulation provided films with important antioxidant properties (evaluated by ABTS. + and FRAP assays) but not antimicrobial activity and the capacity to sense environmental pH changes through the modification of its coloring. The response of these materials against pH changes was evaluated with buffers of different pH (1-14) and simulating their contact with liquid and semisolid foods, and with a container headspace at acid and alkaline pH. Alcoholic extracts were more effective than aqueous ones due to the higher anthocyanins concentration and variety, which exerted a plasticizing effect on the protein matrix. This effect was observed in an increase in film´s elongation and solubility and a decrease in its Young´s modulus. On the other hand, aqueous extracts seemed to favor the protein cross-linking, as they improved films´ mechanical behavior. These materials could be used as active and intelligent packaging of food products, especially those susceptible to oxidation or whose deterioration is accompanied by pH changes.