CRITERION™ DEXTROSE TRYPTONE BROTH

Cat. no. C5630 CRITERION™ Dextrose Tryptone Broth 60gm
Cat. no. C5631 CRITERION™ Dextrose Tryptone Broth 500gm
Cat. no. C5632 CRITERION™ Dextrose Tryptone Broth 2kg
Cat. no. C5633 CRITERION™ Dextrose Tryptone Broth 10kg
Cat. no. C5634 CRITERION™ Dextrose Tryptone Broth 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ Dextrose Tryptone Broth is recommended for the cultivation of thermophilic "flat sour" microorganisms related to the spoilage of food.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.

SUMMARY

The National Canners Association, in the 1930's, suggested use of Dextrose Tryptone Agar for isolation and growth of "flat-sour" organisms from food products. A modification of the agar based formula allows for a broth enrichment and color change to indicate these spoilage causing organisms. "Flat-sour" spoilage of canned foods is caused by Bacillus coagulans (Bacillus thermoacidurans). Growth of these bacteria results in a 0.3 to 0.5 decrease in pH which increases acidity, while the ends of the can remain flat, or unchanged in their pH.(1)

B. coagulans is a bacterium often found in soil, that may appear in canned tomato and dairy products. When conditions within the can are favorable, multiplication of the organism can result in spoilage of the product. Other food spoilage bacteria may be isolated with Dextrose Typtone Broth such as: mesophilic aerobic spore-formers in the genera Bacillus and Sporolactobacillus and thermophilic "flat-sour" spore-formers such as B. stearothermophilus.(2)

Hardy Diagnostics CRITERION™ Dextrose Tryptone Broth formula includes casein peptone (tryptone) as the source of carbon, nitrogen, and vitamins. Dextrose is added as the source of carbohydrates, and bromcresol purple as a pH indicator. This formula has been modified from the original as suggested by the American Public Health Association; the agar was removed, and the concentrations of the remaining ingredients (tryptone and dextrose) were doubled. The broth version has been recommended for canned foods of low to medium acidity (pH 4.5 and higher).(2)

FORMULA*

Gram weight per liter: 30.0gm/L
Tryptone 20.0gm
Dextrose 10.0gm
Bromcresol Purple 0.04gm

Final pH 6.7 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.

STORAGE AND SHELF LIFE

Store the sealed bottle(s) containing dehydrated culture medium at 2-30ºC. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not free-flowing or if the color has changed from its original light greenish-beige.

Store the prepared culture media at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 30.0gm of the dehydrated culture media in 1 liter of distilled or deionized water. Stir to mix thoroughly.

2. Heat as necessary to dissolve completely.

3. Sterilize in the autoclave at 121ºC. for 15 minutes.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. K05.

LIMITATIONS

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as autoclaves, incinerators, and incubators, etc., are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Bacillus stearothermophilus
ATCC ® 12980
A 36-48hr 55°C Aerobic Growth; color change from purple to yellow

User Quality Control

Physical Appearance

CRITERION™ Dextrose Typtone Broth powder should appear homogeneous, free-flowing, and light greenish-beige in color. The prepared media should appear clear, and purple in color.

REFERENCES

1. National Canners Association. 1933. Bacterial standards for sugar.

2. Vanderzant, C. and D.F. Splittstoesser, (ed.). 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. American Public Health Association, Washington, D.C.

3. American Public Health Association. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

4. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods, APHA, Washington, D.C.

5. U.S. Food and Drug Administration. Bacteriological Analytical Manual. AOAC, Arlington, VA.
http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm2006949.htm.

ATCC is a registered trademark of the American Type Culture Collection.

052316gr