Inhibition of foodborne bacteria by antibacterial coatings printed onto food packaging films

Films containing antibacterial compounds could be used for packaging perishable foods such as fresh fish and meat for sea freighting over long distances. However, existing commercialised options (films with nanosilver zeolites or wasabi extract) are only permitted for food contact in certain regions and films containing alternative antibacterial ingredients are required e.g. for exports to Europe. Certain non-volatile phenolic plant extracts have shown promising antibacterial activity against a wide range of foodborne bacteria in in vitro assays and when integrated in coatings for perishable foods such as fish and meat. Extracts rich in gallotannins tend to show stronger antibacterial effects than other phenols such as flavonoids. Such extracts could be coated onto commercial barrier films by means of flexographic printing-a more industrially feasible option than rod coating or solvent casting typically used in antibacterial coating research. The goal of the present work was to investigate the antibacterial effect of printed latex coatings containing extracts rich in gallotannins and other types of phenolic compounds against 16 common spoilage and pathogenic bacteria of fish and meat. The largest zones of inhibition in disk diffusion assays were obtained with plastic films with coatings containing tannic acid alone, followed by tannic acid with phenolic-rich extracts of feijoa skin or mango seed. Significant inhibition was seen for all bacteria. This study shows that coatings with gallotannins as the main active ingredient can be printed onto commercial barrier films to control the bacteria that limit the shelf-life of fresh fish and meat.