Active films based on cocoa extract with antioxidant, antimicrobial and biological applications

Novel films of ethylene-vinyl alcohol copolymer (EVOH) containing flavonoid-rich cocoa were developed. To understand their potential application as active packaging material, antioxidant and antimicrobial properties of the films were determined as well as the antioxidant activity of the release compounds in Caco-2 human epithelial colorectal adenocarcinoma cells. Exposure of the films to aqueous food simulant showed antioxidant capacity. The release of cocoa extract components was dependent on the antioxidant concentration incorporated in the film and on temperature. Cocoa extract and the fraction obtained after in vitro gastrointestinal digestion presented antioxidant activity against oxidative stress induced by hydrogen peroxide in Caco-2 cells. Films with 10%, 15%, and 20% cocoa extract produced bactericidal effect against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella enterica. The application of films to an infant milk formula, previously inoculated with L. monocytogenes, inhibited the growth of bacteria 1.5 log units the first day and showed sustained release, inhibiting 0.52 and 0.76 log units, respectively, by the sixth day, while cocoa powder added directly did not produce any effect.