Application of selected lactic-acid bacteria to control Listeria monocytogenes in soft-ripened “Torta del Casar” cheese

Abstract

“Torta del Casar” cheese is a high-quality cheese made with raw whole sheep's milk with quite broad commercialisation in Europe. This cheese, like other similar ones made with raw milk, are very susceptible to contamination by Listeria monocytogenes. In this work, the effect of two selected protective cultures of Lacticaseibacillus casei 116 and Lactococcus garvieae 151 on the reduction of L. monocytogenes throughout the processing of the traditional “Torta del Casar” was evaluated. Moisture content (%) and water activity (aw) decreased during ripening up to values around 35–38% and 0.93–0.94, respectively. The addition of the selected LAB did not affect physicochemical parameters. Both inoculated LAB strains provoked a relevant reduction in L. monocytogenes counts during the ripening of “Torta del Casar” cheese (up to 5 log CFU/g). Thus, the utilization of any of both strains, Lc. casei 116 and Lco. garvieae 151, as a protective culture in “Torta del Casar” or other similar cheese made with raw milk, could be of great interest to ensure the EU microbiological criteria for this RTE product before the food has left the immediate control of the food business operator, who has produced it, and products placed on the market during their shelf-life.