Influence of cultivation conditions on the growth of Lactobacillus acidophilus, Bifidobacterium sp., and Streptococcus thermophiles, and on the production of organic acids in fermented milks

The parameters influencing the formation of organic acids and the ratio between the optical isomers of lactic acid were evaluated. Five different factors were tested, namely the form of starter, inoculum, temperature of fermentation, time of fermentation, and enhanced non-fat dry matter or addition of whey protein concentrate. Out of them, optimal conditions were chosen for the preparation of fermented milk beverage with ABT culture (Lactobacillus acidophilus, Bifidobacterium sp., Streptococcus thermophilus) with a lowered content of d(-)-lactic acid. The inoculum of bifidobacteria had the only significant effect on the ratio between lactic acid isomers. When 1% v/w used, the ratio of d(-)-lactic acid to l(+)-lactic acid was 0.05. When 5% v/w used, the ratio was 0.02. The addition of dried skimmed milk (max. effect at 12% w/w) enhanced the growth of bifidobacteria, while whey protein concentrate was effective for the growth of lactobacilli. The optimal temperature and time of cultivation were 37°C and 17 ± 0.5 h, respectively.