INFLUENCE OF WATER ACTIVITY ON THE FERMENTATION OF YOGURT MADE WITH EXTRACELLULAR POLYSACCHARIDE-PRODUCING OR NONPRODUCING STARTERS

Ropy and non-ropy strains of Lactobacillus delbrueckii subsp. bulgaric us and Streptococcus thermophilus were studied with respect to their r esistance to reduction of water activity in milk used to produce yogur t. Glycerol reduced the a(w) of the milk considerably, but it was less inhibitory to acid production than sucrose. The ropy strains did not show any advantage over nonropy ones when they were used to produce yo gurt in milk with reduced a(w); their performance was similar to non-p roducer strains in terms of lactic acid production. (C) 1997 Elsevier Science Ltd.