Antimicrobial properties and permeability of Poly lactic Acid nanocomposite films containing Zinc Oxide

Objective(s): Since microbial contamination can reduce the shelf life of the foodstuff and there is a potential for the growth of some pathogen microorganisms, films containing antimicrobial agents were produced, which are also biodegradable. In this study, the effect of 1, 3 and 5% nano-zinc oxide on antimicrobial properties and permeability of poly lactic acid film was investigated. Material and methods: the sample was contaminated with standard strains of gram-negative (Escherichia coli –code of 1399 (ATCC 25992)) and bacteria gram-positive (Staphylococcus aureus–code of 1431 (ATCC 25923)) provided. Diameters of inhibition zones were measured after 24 h incubation of plates at 37 °C, by using Digital Caliper. Also, the permeability to water vapor according to ASTM E96 and oxygen standards according to ASTM D3985 standard was investigated from film surface. Results: The study of antimicrobial properties of films on Escherichia coli and Staphylococcus aureus showed that all three percent of “ZnO” in this study had inhibitory effects and increased the percentage of nano-zinc oxide significantly (P <0.05) increased the inhibitory effects.In this test, the diameter of the control film inhibition zone was zero, which indicates that pure poly lactic acid films do not have antimicrobial activity (P > 0.05). In the study of Water Vapor Permeability (WVP), bio-composite films with 1% and 3% nano-zinc oxide showed a 19% water vapor Permeability enhancement compared to the pure poly-lactic acid. Moreover, adding 3% nano-zinc oxide had an impact on the reduction of permeability to oxygen. Conclusion: Poly lactic acid films containing nano-zinc oxide have a high potential for antimicrobial food packaging applications to enhance the safety of food products.