Inhibition of Streptococcus Lactis in Milk by Fatty Acids

Summary In an effort to determine the cause of the inhibitory property of rancid milk on S.lactis all of the fatty acids common to milk fat were tested for their effect upon the growth of this organism. Caprylic, capric and lauric acids, inhibited growth of S. lactis ; the degree of inhibition increased as the concentration of the acid increased. The effect of myristic acid was doubtful, and none of the other acids tested was found to inhibit the growth of this organism. The inhibitory property of rancid milk and that observed in milk containing fatty acids is not the result of the low surface tension of the milk, but is due to some other unexplained toxic effect of the individual fatty acids.