YSG Agar

Intended Use

Recommended for the detection of Alicyclobacillus in fruit juices in accordance with Official method of IFU.

Composition**

Final pH ( at 25°C): 3.7±0.1

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 20 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C and adjust the pH to 3.7+0.1 with 1N HCl

Principle And Interpretation

Alicyclobacillus species are gram positive aerobic thermophillic, and spore forming acidophilic bacteria. Alicyclobacillus are sometimes called Acidophilic Thermophillic Bacteria (ATB). 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 specially affecting the quality of fruit juice (1,2) and in the beverages, damaging the brand. These bacteria are able to grow at pH values as low as 2.5 and also at elevated temperatures as high as 60°C.

YSG broth is recommended for the enrichment of Alicyclobacillus. Yeast extract in the medium supplies vitamin and growth factors. Glucose serves as an energy source. Soluble starch neutralizes the medium. The low pH of the medium imparts selectivity to the medium. This medium is recommended for the count of Alicyclobacillus in fruit juices (3)

Quality Control

Appearance: Cream to yellow homogeneous free flowing powder

Gelling: Firm, comparable with 1.8% Agar gel

Colour and Clarity of prepared medium: Pale yellow coloured Clear to slightly opalescent gel forms in Petri plates.

Reaction: Reaction of 2.0% w/v aqueous solution at 25°C. pH : 3.7±0.1

pH: 3.60-3.80

Cultural Response

M1753: Cultural characteristics observed after an incubation at 45- 46°C for 3-5 days or 65-66°C for 2-3 days.

Storage and Shelf Life

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

Reference

1. Ceny G., Hennlish W. and K Rocallia-Furchtsaftwerb ducrh Baciilen. Isobioerung and Charakteriseeuing des Verdebserregens-Z hebers Utres Forsch 179: 224-227, 1984.
2. Baungart and Merve S., The Impact of Alicyclobacillus acidoterstris on the Quality of Juices and Soft Drinks Fruit processing 7: 251-254 (2000).
3. Cagnasso Stefano Rapid Screening of Alicyclobacillus acidoterrestris Spoilage of Fruit Juices by Electronic Nose: A Confirmation Study Journal of Sensors Volume 2010 (2010).