Studies to Formulate New Media for the Standard Plate Count of Dairy Products

Abstract

The present Standard Methods agar for the bacterial plate count of dairy products, so-called TGEM. agar, has some undesirable characteristics due to the inclusion of skim milk and beef extract. Studies to find satisfactory media without these ingredients indicated that such media must contain at least: a yeast extract or a plant peptone, an animal peptone, and a carbohydrate. Manipulation of the amts. of ingredients, or substitution or omission of certain ingredients, had predictable quantitative effects on the plate counts. A rapid method for testing the statistical significance of the mean difference of logarithms of paired counts is described and illustrated.