Growth and survival of bifidobacteria and lactic acid bacteria during the fermentation and storage of cultured soymilk drinks Original Research Article

The behaviours of the bifidobacteria B. infantis CCRC 14633 and B. longum B6 and of the lactic acid bacteria Lactobacillus acidophilus CCRC 14079, L. bulgaricus CCRC 14009 and Streptococcus thermophilus CCRC 14085 during the fermentation and storage of cultured soymilk drinks were investigated. Soymilk was found to support the simultaneous growth of the bifidobacteria and L. acidophilus or S. thermophilus, but B. infantis and B. longum both had a deleterious effect on the growth of L. bulgaricus in soymilk. Values for pH, ranging from 6·13 to 4·19, and titratable acidity ranging from 0·09% to 0·25% were noted in soymilk after 48 h of fermentation with various combinations of bifidobacteria and lactic acid bacteria. The viable populations of bifidobacteria and lactic acid bacteria decreased rapidly in the fermented soymilk drinks held at 25°C. When sucrose was added, the reduction in numbers were more pronounced, especially for bifidobacteria. However, the numbers of bifidobacteria and lactic acid bacteria showed no marked change in drinks with or without sucrose during storage for 10 days at 5°C.