Alicyclobacillus Medium (BAT Medium)

Intended Use

BAT Medium is used for the isolation of Alicyclobacillus species from fruit juices.

Composition

Final pH (at 25°C): 4.0±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 10.95 grams in 1000 ml distilled water. Heat if necessary to dissolve the medium completely. Dispense into tubes or flasks as desired. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.

Note: Adjust the pH of the medium to 4.0 ± 0.2 (after sterilization) using 1N H2SO4 or 1N NaOH.

Principle And Interpretation

Alicyclobacillus species are gram positive, aerobic thermophillic, acidophilic bacteria. These spore-forming organisms are able to survive the relatively mild pasteurization temperatures used for fruit juices and drinks and some are able to grow out and cause spoilage of the beverage. Even very low numbers of Alicyclobacillus are able to cause spoilage and produce objectionable flavours and odours in the beverages, damaging the brand (1,2). These bacteria are able to grow at pH values as low as 2.5 and also at elevated temperatures as high as 60°C.

BAT (Bacillus AcidoTerrestris) medium has a pH of 4.0 ± 0.2 which supports growth of Alicyclobacillus and inhibits most of the microbial flora (3). Rest of the microbial flora is inhibited at 60°C, which is the optimum growth temperature for Alicyclobacillus species.

Quality Control

Appearance Cream to yellow homogeneous free flowing powder

Colour and Clarity of prepared medium Light amber coloured clear solution in tubes

Reaction Reaction of 1.1% w/v aqueous solution at 25°C. pH : 4.0±0.2

pH 3.80-4.20

Cultural Response M1561: Cultural characteristics observed after an incubation at 60°C for 48-72 hours.

Storage and Shelf Life

Store below 30°C in tightly closed container and the prepared medium between 2 8°C. Use before expiry date on the label.

Reference

1. Ceny G., W. Hennlish and K Rocallia-Furchtsaftwerb ducrh Baciilen. Isobioerung and Charakteriseeuing des Verdebserregens-Z hebers Utres Forsch 179: 224-227, 1984
2. Baumgart and Merve S. The Impact of Alicyclobacillus acidoterstris on the quality of Juices and Soft Drinks Fruit processing 7 : 251-254 (2000)
3. BAUMGART, J. (2003) Media for detection and enumeration of Alicyclobacillus acidoterretris and Alicyclobacillus acidocaldarius in foods. In handbook of culture Media for Food Microbiology, J.E.L. Corry et al,(Eds.) Elsevier Sci B.V. Amsterdam.