Antibacterial activity of agar-based films containing nisin, cinnamon EO, and ZnO nanoparticles

The antibacterial activity of six essential oils (peppermint, chamomile, cumin, tarragon, dill, and cinnamon) was tested against gram-positive (Listeria monocytogenes and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. The cinnamon EO was selected for the preparation of active films. Twenty-four active films were developed and tested against the foodborne pathogens. In the next study, antimicrobial films were prepared by incorporating nisin (100AU), cinnamon EO (0.6%), and ZnO NPs (10 mg/15 ml) into the agar-based film and tested against seven strains of L. monocytogenes. The antibacterial activity of the bio-nanocomposite was also examined on the population of pathogens which artificially are inoculated in-depth of minced fish over 12 days. Results showed that cinnamon (CEO) had the highest antimicrobial activity. The results revealed that the blend films with ZnO nanoparticles (NPs)+CEO were more effective against gram-positive bacteria than gram-negative bacteria. The strain-specific variation was noticeable for seven tested strains of L.monocytogenes. The films containing nisin and the combination of nisin with ZnO NPs and CEO significantly inhibited the growth of L.monocytogenes on the Tryptic soy agar-NaCl model (p<.05). The results revealed a negligible effect of the active film in minced fish. Practical applicationsThis study developed and utilized antimicrobial nanocomposite films for controlling foodborne pathogens. The antibacterial activity of the active films on the surface of a food model showed that combining ZnO NPs, CEO, and nisin into agar films is a promising method to enhance the food safety.