Ready-to-use media
YSG Medium
Solid medium for the detection and isolation of Alicyclobacillus, in fruit juices and other acidic food, according to IFU Standard Method No. 12.
- Cat. No.
- LC-4113
- Category
- Ready-to-use media
- Format
- 20 tubes
- Storage
- 8 to 25 °C
- Minimum guaranteed shelf life
- 4 months
- Standards
- IFU Method No. 12
Alicyclobacillus have emerged as food spoilage organisms of major significance to the fruit juice industry (Baumgart & Menje, 2000). Spoilage is generally manifested as the formation of off-flavours and odours from compounds such as guaiacol and the halogenated phenols. The economic impact of such incidents can be very high; to date, no human risks are known to be associated with the consumption of juices and other food products containing Alicyclobacillus bacteria.
Key features
Applications
Detection and selective isolation of Alicyclobacillus.
Industry
Juices.
Standards
IFU Method No. 12.
Presentation
20 tubes, 17 x 145 mm, with 20 ± 0.3 mL.
Description and technique
Description
An acidified environment is required to grow alicyclobacilli, and YSG medium supports the growth of all currently known species of Alicyclobacillus (A. acidocaldarius, A. acidoterrestris, A. cycloheptanicus and A. hesperidum). The medium complies with the Standard IFU Method for the detection of taint producing organisms in fruit juices.
The low pH value of the medium, in combination with the high incubation temperature, inhibits the contaminating microbiota. K Agar when incubated at 45 °C supports the growth of predominantly A. acidoterrestris and limited growth of other species of the genus. Therefore, K Agar is used to detect predominantly A. acidoterrestris strains.
Technique
To use, the contents of the tube should be poured into plates. Melt the tube in a microwave or in a water bath at 100 °C. Shake to homogenize the medium before pouring into plates. Do not overheat so as not to alter the consistency of the agar medium.
The IFU Standard provides three methods of detection depending on the sample composition and the time since processing:
- Raw materials (including process water): a heat shock treatment is prescribed, followed by direct plating (optional), filtration or enrichment in liquid medium.
- Final products sampled directly after (heat) processing, where an additional heat shock is unnecessary: pre-incubation of the sample in liquid medium is prescribed.
- Final products taken from the market: pre-incubation of the sample, as per the heat shock treatment. If spoilage is suspected and no alicyclobacilli are detected after direct plating, a heat shock and enrichment is recommended.
In all methods, incubation for 3-5 days at 45 ± 1 °C is prescribed. Count all colonies growing on the YSG Agar as presumptive alicyclobacilli. Confirm the suspicious colonies by further testing.
Presentation
| Presentation | 20 tubes, 17 x 145 mm |
|---|---|
| Filling | 20 ± 0.3 mL |
| Packaging | 17 x 145 mm glass tubes, ink labelled, metal non-injectable cap. 20 tubes per box. |
Composition
| Ingredient | g/L |
|---|---|
| Yeast extract | 2.0 |
| Glucose | 1.0 |
| Soluble starch | 2.0 |
| Agar | 15.0 |
Quality control
Physical/chemical control
| Color | Pale yellow |
|---|---|
| pH | 3.7 ± 0.2 at 25 °C |
Microbiological control
Inoculate: practical range 100 ± 20 CFU; min. 50 CFU (productivity) / 10⁴-10⁶ (selectivity).
Aerobiosis. Incubation at 45 ± 1 °C for 5 days.
| Microorganism | Growth |
|---|---|
| Alicyclobacillus acidoterrestrisATCC 49025 | Good |
| Escherichia coliATCC 25922, WDCM 00013 | Inhibited |
Do not overheat.
Sterility control
Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.
Check at 7 days after incubation in same conditions.
Bibliography
- BAUMGART, J. (2003) Media for detection and enumeration of Alicyclobacillus acidoterrestris 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.
- BAUMGART, J. & S. MENJE (2000) The impact of Alicyclobacillus acidoterrestris on the quality of juices and soft drinks. Fruit Processing 7:251-254.
- CERNY, G., W. HENNLICH & K. PORALLA (1984) Fruchsaftverdeb durch Bazillen: Isolierung und Charakterisierung des Verdebserregers. Z. Lebens. Unter Forsch. 179:224-227.
- ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
- IFU STANDARDS (2004) Method No. 12 on the detection of taint producing Alicyclobacillus in fruit juices. Rev. March 2007.
- WITTHUHN, R.C., W. DUVENAGE & P.A. GOUWS (2007) Evaluation of different growth media for the recovery of the species of Alicyclobacillus. Letters Appl. Microbiol. 45:224-229.
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