Inhibitory strains of lactic streptococci and their significance in the selection of cultures for starter

Inhibitory strains of lactic streptococci have been encountered amongst strains of Str. cremoris isolated from starter and amongst strains of Str. lactis, isolated from sour milk, which had otherwise been regarded as suitable for cheesemaking. 2. Methods are described for determining the concentration of inhibitory substance produced and the effect of these inhibitory strains on a wide selection of lactic streptococci. 3. The significance of the presence of strains of lactic streptococci having inhibitory properties, if incorporated in starters, particularly when the strains are prepared separately and mixed in the vat, is discussed. Recommendations for the exclusion of inhibitory strains from such starter mixtures are made.