Results of Bacterial Plate Counts of Milk on Three Media and at Two Temperatures of Incubation

Abstract

Preceding a change in the culture medium recommended in the 7th edition of the Standard Methods for the Examination of Dairy Products the author carried out comparative tests with the old standard agar, the new standard agar, and the agar recommended by the Amer. Assoc. Med. Milk Comm. for use with certified milk. Plates were incubated at 37[degree] and 32[degree]C. The use of the new tryptone-glucose-extract-milk agar at 37[degree] gave a variable increase over the plate count on standard nutrient agar. Incubation at 32[degree]C in combination with the modified agars gave greater increases in plate counts than the use of any of these agars at 37[degree]C. Attempts to translate counts on the new agars in terms of counts on the old agar are likely to be misleading.