thermophilus
and L. delbrueckii subsp. bulgaricus were inoculated
together into either cows' milk or soy beverage. Twelve hours
were required to reach a pH of 4.3 in both cases (Fig. 1). The S.
thermophilus and L. delbrueckii subsp. bulgaricus strains used
in this study grew well in the soy beverage and their population
stabilized after 6 h and 10 h incubation, respectively. When
cows' milk was inoculated with both S. thermophilus and
L. delbrueckii subsp. bulgaricus, their numbers increased
steadily during the 12 h fermentation. After 12 h, the numbers
of S. thermophilus in both the cows' milk and the soy beverage
were higher than those of L. delbrueckii subsp. bulgaricus.