Antilisterial properties of PVOH-based films embedded with Lactococcus lactis subsp. lactis

Abstract

The incorporation of lactic acid bacteria (LAB) in edible films and coatings has recently emerged as an innovative strategy to provide packaging films with new functionalities in order to ensure food quality and safety. In this work, bioactive films were made by incorporating Lactococcus lactis subsp. lactis in cast polyvinyl alcohol (PVOH) matrices, alone or blended with a small percentage of proteins, protein hydrolysates, or yeast extract, and the effect of incorporating them on the morphology and optical properties of the PVOH films was studied. Moreover, the viability of L. lactis in the films developed stored at 20 °C and 43.2% relative humidity for four weeks, and the antimicrobial activity against L. monocytogenes were determined.The thickness, color properties, and morphology of the films incorporating LAB and nutrients did not show significant differences compared with plain PVOH films, but moisture content increased slightly with nutrient incorporation. L. lactis remained viable for 4 weeks of storage, but viability depended on the matrix composition, being lower in plain PVOH films and higher in films supplemented with proteins, hydrolysates, or yeast extract. The highest antimicrobial activity was observed in PVOH matrices with hydrolyzed gelatin or casein, and the lowest in plain PVOH films. The growth of L. lactis was similar in all the films after incubation in contact with L. monocytogenes at 37 °C in liquid medium, regardless of the initial concentration. The films developed could be applied in the design of food packages with the purpose of inhibiting growth of L. monocytogenes.