Investigating of Antifungal Activity of Polylactic Acid Film Containing Iron Nanoparticles in a Food System

Food contamination by fungi threatens human health. Active packaging containing antifungal compounds is a novel method to increase the safety and preservation of food. The aim of this study was to produce and investigate the antifungal properties of poly-lactic acid active film containing iron nanoparticles in grape juice packaging. Poly-lactic acid nanocomposite films were prepared by casting method through adding different amounts of nanoparticles (0, 2 and 4%) to 4% (w/w) solution of poly-lactic acid in chloroform and antifungal effect of films were investigated in in vitro and grape juice packaging. For this purpose, circular disks (6 mm) of film were prepared and placed on Potato Dextrose Agar media culture inoculated whit Aspergillus niger, Penicillium notatum, Botrytis cinerea. The diameter of the zone of inhibition was reported based on millimeters after 5 days of incubation of the plates at 27 ° C. In order to investigate the antifungal effect of nanocomposite in packaging of grape juice, 5×104 cfu/ml of these molds were inoculated to pasteurized grape juice and then packed with termal sewing and after a 15-days period, the molds population was counted. The distribution of nanoparticles in the polymer, was uniform at concentration of 2% and formed agglomerate at concentration of 4%. The results of the disc diffusion test showed that adding of nanoparticles to the film caused antifungal effect against the tested fungi and this property increased with increasing percentage of nanoparticles. Also, the results of the study on the antifungal effect in grape juice packaging in the 15-days period showed that the population of fungi had an inverse relationship with concentrations of iron nanoparticles in grape juice samples. A. niger showed the most and B. sinera showed the least resistance to this nanoparticle. Significant compatibility between iron nanoparticles and poly lactic acid provides the possibility of producing poly-lactic acid nanocomposite as an alternative for synthetic polymers from petroleum derivatives. Iron nanoparticles produce anti-fungal effects through the leakage of lactase dehydrogenase from the cell wall, impairment in mitochondrial function, chromosomes compression, and production of free radicals of oxygen. Due to the antifungal effect of iron nanoparticles, its application in poly-lactic acid film decreases fungal growth and, as a result, increases the shelf-life of foods.