A numerical taxonomic study of psychrotrophic bacteria associated with lipolytic spoilage of raw milk.

ABSTRACT

Raw milk samples were stored for 1-4 d and examined for bacterial growth and lipase activity. Thirty-six samples in which an increase in the heat-stable lipase activity was observed during storage were selected for further study. From these raw milk samples 205 lipolytic psychrotrophic strains were selected using butterfat agar and subsequently characterized with 86 taxonomic tests. Complete linkage cluster analysis of the taxonomic data produced two major and six minor clusters at the 83% similarity level. Pseudomonas fluorescens and Ps. fragi accounted for 63.9 and 31.2%, respectively, of the isolates.