Dextrose Tryptone Agar is recommended for the determination of mesophilic and thermophilic bacteria in sweetening agents used in frozen desserts. Bromcresol purple is used as a pH indicator. When isolating thermophilic bacteria use 55°C as a plating temperature. Dextrose Tryptone Agar is a agar medium used for the cultivation of "FLAT SOUR" organisms related to the spoilage of food products. (Alpha Biosciences # D04-110-500gm)
Use: Dextrose Tryptone Agar is a agar medium used for the cultivation of "FLAT SOUR" organisms related to the spoilage of food products.
Description: Dextrose Tryptone Agar is recommended for the determination of mesophilic and thermophilic bacteria in sweetening agents used in frozen desserts. Bromcresol purple is used as a pH indicator. When isolating thermophilic bacteria use 55°C as a plating temperature.
Formula* per Liter:
- Tryptone .......................................... 10.0g
- Dextrose ...................................... 5.0g
- Bromcresol Purple ......................... 0.04g
- Agar ........................................... 15.0g
Final pH: 6.7 ± 0.2 at 25.0°C
* Grams per liter may be adj. or formula supplemented to obtain desired performance
Preparation: Mix 30 grams of the dehydrated medium in one Liter of purified water until evenly dispersed. Heat with repeated stirring and boil for minute to dissolve completely. Distribute and autoclave at 121°C for 15 minutes.
Quality Control Specifications:
- The powder is homogeneous, free-flowing and light greenish beige.
- Visually the prepared medium is clear to slightly hazy and purple.
- Expected cultural response after 36-48 hours at 55.0°C.
Organism                                                                               Result
Bacillus coagulans ATCC 7050Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Growth, yellow colonies
Bacillus stearothermophilus ATCC 7953Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Growth, yellow colonies
Storage: Store the sealed bottle containing the dehydrated medium at 2 to 8.0°C. Once opened and recapped, place the container in a low humidity environment at the same storage temperature. Protect it from moisture and light. The dehydrated medium should be discarded if it is not free flowing or if the color has changed from the original light greenish beige color.
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