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

Abstract

The fermentable carbohydrates and other milk constituents in skim-milk agar make it a desirable medium to use in the routine control of market milk and other dairy products. The skim-milk agar counts on 618 samples of pasteurized milk were, on the average, two to four times as large as the corresponding counts on standard agar. The counts on 137 samples of raw milk were only slightly higher. The colonies were much larger and consequently could be counted with greater ease and rapidity. The slight opacity of the medium prevents the glare often experienced when artificial lighting devices are used. Acid-producing and protein-digesting types of bacteria can be differentiated on this medium. It supports the growth of bacteria responsible for mastitis in cows. It is simple and easy to make and no more expensive than the present standard agar. © 1935, American Dairy Science Association. All rights reserved.