Abstract
Twenty-seven samples of 11 brands of yoghurt and 67 samples of 34 brands of acid-milk-drinks were examined bacteriologically and special emphasis were placed on the taxonomic problems of lactobacilli. Results obtaind were as follows:
1) Irrespective of brands the viable counts in the yoghurt were about 108 to 109 per ml. of samples and lactobacilli detected were identified as L. bulgaricus and L. jugurti. In one half of samples streptococci were also detected simultaneously.
2) The lactobacilli in the acid-milk-drinks varied considerably, both quantitatively and qualitatively, according to brands. Generally the viable counts of the acid-milk-drinks were approximately less than one tenth of those of yoghurt. Eighteen samples of 12 brands showed less than 106 per ml. of samples. No lactic acid bacteria were detected from 6 samples of 4 brands. The lactobacilli were identified as L. jugurti, L. casei type I (L. casei var. rhamnosus) and L. casei type II (L. casei var. casei). No streptococci were detected from these products.
3) The acid-milk-drinks claimed to contain “active lactic acid bacteria” contained only L. jugurti and had less counts of lactic acid bacteria than yoghurt. The acid-milk-drinks claimed to contain L. acidophilus contained L. casei type II instead of L. acidophilus. It seems that strains in these products are wrongly designated.
4) In this connection it must be pointed out that 3 strains designated as L. acidophilus in the Type Culture Collection in Japan are wrongly named: IAM 1084 and OUT 8237 should be belonged to L. casei var. rhamnosus, and IAM 1043 to L. casei var. casei.
