Dextrose Tryptone Agar

Dextrose Tryptone Agar is used for isolation of mesophilic or thermophilic spoilage microorganisms from food in a laboratory setting. Dextrose Tryptone Agar is not intended for use in the diagnosis of disease or other conditions in humans.

Dextrose Tryptone Agar evolved from research by Williams, while studying the cultivation and enumeration of thermophilic bacteria caused by "flat-sour" spoilage of canned foods. In the 1930's, the National Canners Association specified the use of Dextrose Tryptone Agar for isolating "flat sour" organisms from food products. "Flat sour" spoilage of canned foods is caused by Bacillus coagulans (Bacillus thermoacidurans). Bacterial growth results in a 0.3 – 0.5 drop in pH, while ends of the can remain flat. B. coagulans is a soil microorganism, found in canned tomato products and dairy products. Conditions favorable for organism growth can result in spoilage of food products.

Dextrose Tryptone Agar can be used to isolate other food spoilage bacteria including mesophilic, aerobic spore-formers and thermophilic "flat sour" spore-formers such as B. stearothermophilus.


Formula Liter
Enzymatic Digest of Casein 10 g
Dextrose 5 g
Bromcresol Purple 0.04 g
Agar 15 g

Final pH: 6.7 ± 0.2 at 25°C
Formula may be adjusted and/or supplemented as required to meet performance specifications.


  1. Suspend 30 g of the medium in one liter of purified water.
  2. Heat with frequent agitation and boil for one minute to completely dissolve the medium.
  3. Autoclave at 121°C for 15 minutes.

Order Details

Product # Product Description
7340A Dextrose Tryptone Agar, 500 g
7340T Dextrose Tryptone Agar, 5 kg