The Advantages of Skim-Milk Agar for the Determination of the Sanitary Quality of Market Milk

Abstract

Attention was called by Sherman (1) to the advantages in using an agar containing a fermentable carbohydrate in the bacteriological control of market milk. He presented data which showed that the colonies of bacteria normally present in milk were two to ten times larger on lactose agar than on plain agar. He made comparative bacterial counts on plain and lactose agar which showed an average increase, in favor of lactose agar, of 43 per cent on raw milk and 378 per cent on pasteurized milk. Sherman mentioned that "glucose is apparently just as efficient as is lactose, both as to number and size of colonies," and that "since glucose is cheaper it should perhaps be recommended as the standard for routine work." He also suggested that the amount of sugar could be reduced to 0.1 per cent "without impairing the value of the medium." Simmons (2), and others, have confirmed Sherman's findings.