Abstract
In sterilized skim milk or sterilized l0% solution of dry skim milk at 120°C for 15 min, Lactobacillus bulgaricus, Lactobacillus helveticus and Streptococcus lactis were cultivated for 7 days at given temperature.
Both NCN (non casein type nitrogen) content and pH in each culture of lactic acid bacteria were rapidly decreased until 2 days after cultivation. But NCN content increased and the pH change got small after 3 days cultivation.
Caseins prepared from the cultures of these three kinds of lactic acid bacteria were examined electrophoretically. From the results of electrophoresis of these caseins, we have concluded that β-casein could be hydrolyzed by these lactic acid bacteria. And, it seemed that α-casein could not be hydrolyzed by these lactic acid bacteria.
Rennet easily hydrolyzed casein treated with L. bulgaricus and L. helveticus but hardly hydrolyzed that treated with S. lactis compared with control-casein. Caseins treated with L. bulgaricus and L. helveticus were hydrolyzed easier than control-casein.
