Technological properties of lactic acid bacteria isolated from "Formagèla Valseriana

Several factors influence the development of the organoleptic characteristics of the cheese: type and microbiological quality of milk, cheese-making technology, ripening conditions and others. However, lactic acid bacteria (LAB) play a principal role in releasing specific compounds responsible for flavor development; their most important property is acid production, but also the indirect contribution to the texture. Another important parameter is the redox potential (Eh), which contributes to the microbial quality, creates a balanced flavor development and protects compounds from oxidation. ,,Formagèla Valseriana" is a traditional Italian farmhouse cheese, manufactured from raw-milk, without addition of starter cultures in the alpine valley Valle Seriana. Ripening process takes place in natural caves for more than 30 days. The aim of this study was to value and to characterize the dominant microflora of Formagèla Valseriana cheese produced in mountain and plain farmhouses. Microbial changes were examined during the manufacture, after 1 and 30 days of ripening. Strains of indigenous LAB were isolated, identified and characterized according to their acidifying, proteolytic and reducing activities. Analyses show high level (108 cfu/g) of many LAB species and interesting differences between microflora occurring both in curd and cheese and in mountain and plain samples. Differences in technological properties inside the species were found. Lactococcus lactis ssp. lactis predominated, strains from curd showed lower acidifying and higher reducing activity. Other main species were St. thermophilus and Enterococcus spp. (none of the strains were resistant to vancomycin). Lc. garviae and E. durans were isolated only from curd, while all Lactobacillus strains come from cheese. Results suggest that specificity and peculiar sensory characteristics of traditional cheeses are strictly related to the high level of biodiversity of the indigenous microflora. Over the centuries the technologies of these cheeses have selected bacterial ecosystems so complex that it is impossible to reproduce them exactly and dangerous to wipe out.