Changes in the Microflora of Valdeteja Raw Goat's Milk Cheese throughout Manufacturing and Ripening

Abstract

Changes in the microbiological flora of Valdeteja, a ripened home-made raw goat's milk cheese produced in northwest Spain, were studied during the manufacture and ripening processes using the spiral plating method. High counts of all microbial groups were observed in milk (7.66, 7.57, 6.13, 6.91, 2.47, 5.18, 3.27 and 3.85 log 10 cfu/g for aerobic mesophilic bacteria, lactococci, lactobacilli, leuconostocs, enterococci, Enterobacteriaceae, Micrococcaceae and moulds and yeasts, respectively). Counts increased between 0.76 and 1.96 log units from milk to curd. Lactic acid bacteria (lactococci, lactobacilli and leuconostocs) were the dominant microorganisms throughout ripening. Lactococci dominated over the lactobacilli up to day 27 of ripening. Leuconostocs were stable from day 2 of ripening. The final levels of typical enterococci were 3.62 log 10 cfu/g. Aerobic mesophilic bacteria, Enterobacteriaceae and Micrococcaceae reached their maximum in curd and decreased significantly throughout ripening. The decrease of Enterobacteriaceae was very marked, although they did not completely disappear at the end of the ripening process (2.74 log 10 cfu/g). Moulds and yeasts counts increased significantly during ripening, giving final levels of 6.09 log 10 cfu/g. A strong correlation ( P<0.001) was found between pH and lactobacilli ( R=−0.87), leuconostocs ( R=−0.82) and moulds and yeasts ( R=−0.74) and between a w and various microbial groups (e.g. Enterobacteriaceae R=0.83).