EVALUATION OF NEW ISOLATES OF LACTIC ACID BACTERIA AS A STARTER FOR CULTURED MILK PRODUCTION

Abstract

Strains of lactic acid bacteria belonging to Lactococcus lactis species were isolated from naturally fermented milk products in Ethiopia and evaluated as starter cultures noting for milk coagulation time. organic acid metabolism, production of volatile aroma compounds (acetaldehyde, diacetyl and acetoin). Ten strains of Lactococcus lactis were selected for further evaluation as a single strain starter culture for the production of cultured milk. The strains of Lactococcus lactis varied significantly in production of volatile compounds and metabolism of organic acids. The sensory properties of the cultured milk also differed when the different strains were used as a starter culture. Although flavour scores and concentration of individual volatile compounds showed little correlation. variations in sensory attributes of the products suggested that use of promising strains among the new isolates as a starter could enhance production of stable and good quality cultured milk. Further evaluation of these strains, as mixed cultures under different conditions is required to determine strains that complement each other for the desired metabolic property.