DEHYDRATED CULTURE MEDIA 67 



as heating in the acid state will hydrolyze the agar, reducing its solidifying 

 properties so that the resulting medium will be soft or mushy. 

 One pound of Bacto-Malt Agar will make 10 liters of medium. 



1 Standard Methods for the Examination ^ J. Dairy Science, 13:394:1930. 

 of Dairy Products, 9th Edition: 181 : 1948. '^ J. Dairy Science, 16:289:1933. 



2 Abs. Bact., 3:6:1919. ^ J. Dairy Science, 16:141:1933. 



2 Thom and Church: The Aspergilli, 1926. ^ Cereal Laboratory Methods, 5th Edition: 



* J. Bact., 8:586:1923. 132,135:1947. 



s Can. Dept. Agr. Pamphlet, 92-N.S. 1° J. Dairy Science, 32:101,1949. 



BACTO 



DEXTROSE TRYPTONE AGAR (B80) 



DEHYDRATED 



Bacto-Tryptone 10 g. 



Bacto-Dextrose 5 g. 



Bacto-Agar 15 g. 



Bacto-Brom Cresol Purple 0.04 g. 



Bacto-Dextrose Tryptone Agar is recommended for the determination of 

 thermophilic "flat sour" organisms associated with the spoilage of food products. 

 It was developed in collaboration with the research laboratories of the National 

 Canners Association and is recommended for that purpose in their "Bacterial 

 Standards for Sugar."^ For plate count of mesophilic or thermophilic aerobes in 

 sweetening agents used in frozen desserts, "Standard Methods for the Examina- 

 tion of Dairy Products"- recommend the use of Bacto-Dextrose Tryptone Agar. 



Bacto-Dextrose Tryptone Agar is primarily used as a plating medium anc' 

 when employed for determining thermophiles, it should be incubated at 55 °C. 

 for 36-48 hours in an incubator sufficiently humid to prevent drying of the 

 medium. 



To rehydrate the medium, suspend 30 grams of Bacto-Dextrose Tryptone 

 Agar in 1000 ml. of cold distilled water and heat to boiling to dissolve the 

 medium completely. Distribute in tubes or flasks and sterilize in the autoclave 

 for 15 minutes at 15 pounds pressure (121°C.). The final reaction of the medium 

 will be pH 6.7. 



One pound of Bacto-Dextrose Tryptone Agar will make 15.1 liters of medium. 



^ Pub, of National Canners Association, 1933. 2 Standard Methods for the Examination 



of Dairy Products, 9th Edition: 185: 1948. 



ADDITIONAL MEDIA 



Media as used in "Standard Methods for the Examination of Dairy Products" 

 procedures are listed below. Complete discussions of these media will be found 

 on the pages indicated. 



Heart Infusion Broth page 80 



Cooked Meat Medium page 85 



Lactose Broth page 30 



Nutrient Broth page 29 



Tetrathionate Broth page 157 



Tryptose Phosphate Broth page 100 



Azide Blood Agar Base page 155 



Bismuth Sulfite Agar page 139 



Endo Agar page 34 



Levine E.M.B. Agar page 35 



MacConkey Agar page 131 



S S Agar page 134 



