Bacterial communities of the traditional raw ewe’s milk cheese “Torta del Casar” made without the addition of a starter

Abstract

The objective of this work was to study the growth and development of fortuitous flora and food pathogens in the traditional Spanish cheese “Torta del Casar”. Sixteen batches of “Torta del Casar” were manufactured from the same unpasteurized Merino ewe’s milk, using Cynara cardunculus L. rennets, corresponding to 16 plants, one for each batch. The cheeses were classified based on their texture spreadability analysis data (TSA) into four clusters, from very creamy to not creamy cheeses. Although there were no differences between the counts of different microbial groups in the different clusters of cheese, the microorganism isolated did differ between clusters, especially between the Group 1 cluster (less creamy cheese) and Group 4 (creamiest cheese), with the most notable isolates in the latter being a LAB Lactococcus lactis subsp. cremoris, and the enterobacteria Serratia proteamaculans and Enterococcus devriesei. Pathogen development was similar in all four groups of cheeses. Small differences were found for some pathogens (Listeria spp. and Salmonella spp.) which may have been due to interference with the different autochthonous microbiota. Indeed, the different autochthonous microbiota appears to influence the texture of the cheeses and the development of pathogens in them.