Inhibitory activity against Listeria monocytogenes by soy-protein edible film containing grape seed extract, nisin, and malic acid

The frequent outbreaks of food-borne illness necessitate development of intervention strategies, including the use of natural antimicrobials. Listeria monocytogenes is one of the most important bacterial pathogens that recently has caused a significant number of outbreaks. With the aim of finding potent natural agents that can minimize pathogen contamination concerns, this study evaluated the inhibitory activities against L. monocytogenes of grape seed extract (GSE), malic acid (M), nisin (N), and combinations thereof incorporated into soy-protein edible films. Soyprotein films with/without addition of antimicrobial agents (GSE: 1%, Nisin: 10,000 IU/g, Malic acid: 1%, and their combinations) were prepared and evaluated for anti-listerial activities. The highest inhibitory activity after 1 h incubation at 25°C was found in the treatment containing GSE, nisin, and malic acid, which produced reductions of log 3.7 colony-forming units (CFU)/ ml as compared to control film without the addition of antimicrobial agents. These data demonstrated that the GSE, nisin, and malic acid combination incorporated into soy-protein edible films is very effective in inhibiting L. monocytogenes growth at 25°C and has potential for applications on a variety of food products to help prevent L. monocytogenes contamination and growth