Studies on the Milk Component (s) Participating in Uneven Distribution of Lactococcus lactis subsp. cremoris in Milk

Abstract

In cottage cheese manufacture, spongy curd formation in the bottom of cheese vat has been reported by several researchers. It was said that this spongy curd was caused by an uneven distribution of starter bacteria resulting from their agglutination, and this phenomenon has been a big problem in the processing of fermented milk products. Although the participation of immunoglobulins in milk in this bacterial agglutination has been shown, the mechanism of this agglutination remained unknown. So, in this study, the agglutination of test strains of Lactococcus lactic subsp. cremoris in milk was confirmed and the mechanism of this agglutination was elucidated. As the results, it was found that IgM bound to the bacterial cells in all the test eleven strains. The immunochemical technique clearly showed that the common specific five polypeptides (M. W.; 22-52kDa) existed in the bacterial cells of test strains strongly agglutinated by IgM. On the other hand, in case of test strains weakly agglutinated by IgM, it was thought that either these polypeptides did not completely exist in the bacterial cells or if even present, their strength of binding with IgM was weak. The close relation between their agglutination property by IgM and their strength of binding with IgM was confirmed. It was suggested that the agglutination by IgM originated from the connection of these polypeptides with IgM.