Raw milk flora affects composition and quality of Bergkase. 1. Microbiology and fermentation compounds

Experimental samples of Bergkase, an Austrian regional hard cheese variety usually made from raw milk, were produced from raw or pasteurised milks in parallel to evaluate the influence of the indigenous microflora on microbiological composition and selected fermentation compounds. Facultatively heterofermentative lactobacilli (FHL) dominated the non-starter flora in cheeses made from raw milk. Viable numbers increased from 10(4)-10(6) cfu.g(-1) at the age of 1 week to reach their final level of 10(8) cfu.g(-1) within the first month of ripening. In contrast, cheeses made from pasteurised milk exhibited FHL counts which were at least three orders of magnitude lower or even undetectable. In the raw milk cheeses, the development of organic acids during maturation differed from that in the pasteurised ones, and was dependent on the number and the metabolic activity of the microorganisms. Differences in the citrate metabolism and in propionic acid fermentation, which occurred in raw milk cheeses only, can be attributed to the occurrence of FHL and propionic acid bacteria, respectively. (C) Inra/Elsevier, Paris.