The catechins in the cocoa extract inhibit the growth of all the microorganisms tested. There were no differences in the effect between gram-negative and gram-positive bacteria, which have different structures. Gram-negative bacteria include E. coli and Salmonella; gram-positive bacteria include Staphylococcus and Streptococcus. The films were very effective at inhibiting the growth of Listeria monocytogenes in infant milk.
In addition, when the films were exposed to aqueous food simulant, it demonstrated antioxidant capacity, which could extend the shelf life of foods. Films with 10%, 15%, and 20% cocoa extract had bactericidal effect against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella enterica. No cocoa-based films are currently in use in food packaging.