The Germicidal Action of Raw Milk upon an Organism of the Sweet Curdling Type

Abstract

Summary Certain samples of mixed raw milk exerted a marked restraining action upon an organism capable of rapidly producing a sweet curdling type of fermentation. This action was present in the milk over a period of several months. Coagulation produced by the sweet curdler was delayed from three and one-half to six hours in different samples of mixed raw milk. Coagulation usually occurred when the sweet curdler attained a population of from 10 to 40million. The marked germicidal activity in this study was confined to Jersey milk. Under the conditions of these experiments, S. lactis exerted but little influence upon the development of the sweet curdler and was only slightly restrained by the bactericidal activity of the milk. Both S. lactis and the sweet curdler multiplied more rapidly in the heated milk than in the non-germicidal raw milk. The difference was relatively small during the first eight hours, but thereafter was usually large. These observations indicate that under certain conditions a strong germicidal action may be of distinct value in protecting the milk supply.