Study on antimicrobial activity of a food packaging material containing potassium sorbate

The feasibility of EVA/LLDPE films containing 1, 2 and 5% (w/w) K-sorbate t o inhibit microbial growth and as a consequence prolong shelf-life of foods was investigated. Based on weight loss experiments it was shown that K-sor bate is very suitable for incorporation in LLDPE because of its heat stabil ity during extrusion. After 3 weeks, resp. 6.4, 2.8 and 5.7% of the incorpo rated sorbic acid was released into distilled water from films containing r esp. 1, 2 and 5% (whv) K-sorbate. The very limited migration of K-sorbate m ay be explained by the incompatibility of the polar salt with the apolar LL DPE. This limited migration could explain the very small inhibitory effect of the K-sorbate films on the growth of Candida spp., Pichia spp., Trichosp oron spp, and Penicillium spp. During storage at 7 degrees C of cheese pack aged in a 5% (w/w) K-sorbate film, no significant differences could be obse rved for yeast and mould growth on the cheese cubes compared to a reference film. The concentration of sorbic acid in the cheese did not exceed 14 ppm . This is much lower than the 1000 ppm K-sorbate needed to inhibit microbia l growth. The results of this study confirm that the K-sorbate incorporated LLDPE film is not able to inhibit microbial growth in vitro on inoculated media and in vivo on cheese due to the insufficient release of K-sorbate fr om the film.