CHARACTERIZATION OF THE LACTIC-ACID BACTERIA IN ARTISANAL DAIRY-PRODUCTS

In all, 4379 isolates from 35 products, including 24 artisanal cheeses , were surveyed with a view to identifying strains that could be used as starters in commercial dairy fermentations. Of the isolates, 38% we re classified as Lactococcus, 17% as Enterococcus, 14% as Stre;otococc us thermophilus, 12% as mesophilic Lactobacillus, 10% as Leuconostoc a nd 9% as thermophilic Lactobacillus. Acid production by the isolates v aried considerably. Of the 1582 isolates of Lactococcus and 482 isolat es of mesophilic Lactobacillus tested, only 8 and 2% respectively prod uced sufficient acid to lower the pH of milk to < 5.3 in 6 h at 30 deg rees C. In contrast, 53, 32 and 13% of Str. thermophilus, thermophilic Lactobacillus and Enterococcus isolates respectively reduced the pH t o 5.3. These isolates were found only in some French, Italian and Gree k cheeses. Bacteriocins mere produced by 11% of the 2257 isolates test ed and 26 of them produced broad-spectrum bacteriocins which inhibited at least eight of the ten target strains used, which included lactic acid bacteria, clostridia and Listeria innocua. The most proteolytic o f the 2469 isolates tested were Str. thermophilus from Fontina cheese followed by Enterococcus from Fiore Sardo and Toma cheese and thermoph ilic Lactobacillus from all sources. Exopolysaccharides were produced by 5.3% of the 2224 isolates tested.