Starter culture activity in refrigerated fermented soymilk

The refrigerated shelf life of soymilk fermented with single cultures of Lactobacillus fermentum, L. casei, Streptococcus salivarius subsp. thermophilus, and Bifidobacterium longum was evaluated. During storage at 4 degrees C for 28 days, the stability of the microflora differed markedly among the starter cultures. After 28 days, the average numbers of S. salivarius subsp. thermophilus decreased by two log cycles to 6.0 X 10(7) CFU/ml, whereas those of L. casei increased gradually by more than two log cycles to 4.6 X 10(9) CFU/ml. Numbers of B. longum and L. fermentum remained moderately high (8.7 x 10(8) CFU/ mi and 3.7 x 10(8) CFU/ml, respectively) even after 28 days of storage. S. salivarius subsp. thermophilus and L. casei continued to metabolize sucrose during the storage period, but the pattern of consumption was different among the strains. The other starter cultures did not seem to have significant activity (P > 0.05) on the residual sugars. In most cases, L(+)-lactate predominated.