Microbiological study of Leon raw cow-milk cheese, a Spanish craft variety

The levels of several microbial groups (aerobic mesophilic flora, aerobic psychrotrophic flora, lactic acid bacteria, Micrococcaceae, enterococci, Enterobacteriaceae, and molds and yeasts), and some biochemical parameters were investigated during the manufacture and ripening of four batches of Leon cow cheese produced from raw milk without the addition of starter cultures. The study of the microbial characteristics of this cheese constitutes the first step towards the establishment of a starter culture which would allow the making of a product both more uniform and safer from the point of view of health. The total microbial counts were high throughout the elaboration and ripening. Almost all the microbial groups reached their maximum counts in curd and afterwards dropped throughout the ripening process. The greatest drop was shown by Enterobacteriaceae, which had disappeared after 3 months of ripening. Lactic acid bacteria were the major microbial group, reaching counts similar to the total aerobic mesophilic flora at all sampling points. Lactococcus lactis subsp. lactis dominated in milk (62.5% of the isolates obtained in de Man-Rogosa-Sharpe (MRS) agar at this sampling point), curd (82.5% of the isolates obtained at this sampling point) and one-week-old cheese (85% of isolates obtained at this sampling point), while Lactobacillus casei subsp. casei was the most predominant species in eight-week-old cheese (55% of isolates obtained at this sampling point) and twelve-week-old cheese (47.5% of isolates obtained at this sampling point). According to our data, a starter suitable for the production of Leon cow cheese would be made up of these two species. Some species of Leuconostoc or enterococci could also be added to this starter with the aim of improving the organoleptic characteristics of the final product or to emphasize the characteristics of this variety.