DEHYDRATED CULTURE MEDIA 57 



1000 ml. of distilled water and distribute in 10 ml. quantities in fermentation 

 tubes. Sterilize by autoclaving for 15 minutes at 15 pounds pressure (121°C.). 

 The final reaction of the medium will be pH 7.3. 



When the medium is to be used with inocula greater than 1 ml., particular 

 care must be taken to preserve the correct concentration of the ingredients 

 after dilution with the sample. For example, if 10 ml. of water are to be added 

 to 10 ml. of medium, the medium should be prepared in double strength. 



One pound of Bacto-MacConkey Broth will make 12.9 liters of medium. 



1 Centr. Bakt., 29:740:1901. 2 J. Hyg., 8:322:1908. 



2 J- Hyg., 5:333:1905. 



MEDIA FOR THE EXAMINATION OF 

 DAIRY AND OTHER FOOD PRODUCTS 



The dehydrated culture media listed in this section are recommended for the 

 examination of milk and other dairy products. In many cases the formulae con- 

 form to those in "Standard Methods of the Examination of Dairy Products" of 

 the American Public Health Association and the Association of Official Agricul- 

 tural Chemists, Ninth Edition 1948, and "Methods and Standards for the Pro- 

 duction of Certified Milk," 1950, of the American Association of Medical Milk 

 Commissions, or other official procedures. 



Carefully selected standardized ingredients are used in the exact proportions 

 specified in the "Standard Methods" formulae. The reaction of each medium is 

 adjusted so that the final reaction of each preparation made from the dehydrated 

 product will fall within the range of pH recommended in "Standard Methods." 



The American Public Health Association has permitted the use of dehydrated 

 media of "Standard Methods" composition continuously since 1923 in every 

 edition of its "Standard Methods of Milk Analysis," including the current Ninth 

 Edition of "Standard Methods for the Examination of Dairy Products." 



A guide for the selection of culture media listed in this section is given on 

 page 25. 



"STANDARD METHODS" MEDIA 



The media listed in this section conform to the specifications for the examina- 

 tion of milk and other dairy products as outlined in the "Standard Methods for 

 the Examination of Dairy Products," Ninth Edition. 



BACTO 



TRYPTONE GLUCOSE EXTRACT AGAR (B2) 



DEHYDRATED 



Bacto-Beef Extract 3 g. 



Bacto-Tryptone 5 g. 



Bacto-Dextrose (<i-glucose) 1 g. 



Bacto-Agar 15 g. 



Bacto-Tryptone Glucose Extract Agar is recommended for use in determining 

 the standard plate count of milk and other dairy products according to the 



