A. Y. SADOVSKI; I. FOREMAN

Characterization of psychrotrophic bacteria from cultured milk has shown that most (72%) of the psychrotrophs which were isolated originated from the starter culture. Streptococcus lactis subsp. diacetilactis was the most abundant organism and dominated both Streptococcus cremoris and Leuconostoc cremoris, which was the least abundant. The doubling time of S. lactis subsp. diacetilactis at 7 C was 20 h and 54 h in Trypticase Soy Broth at pH 7.0 and 5.0, respectively. This indicates a growth potential which could be significant to the quality of the product over a long storage period. Psychrotrophic coliforms which had optimal growth temperatures within the range of 15 to 30 C could also be found in small numbers. Their survival in the product was limited and it was concluded that they have little effect on shelf-life.