SOP: Preparation of Oily Material for Microbiological Examination

GIFSQ — Global Institute for Food Safety & Quality

Principle

Oily material will not mix with water-based diluents, so it is first dispersed in an emulsifying diluent — gum tragacanth with ethanol, dextrose and sodium tauroglycocholate, sterilized under pressure — and dilutions for examination are made from that emulsion in warm diluent.

Apparatus required

• Autoclave
• Sterile containers

Reagents

a. Gum tragacanth — 1.5 g, the emulsifying agent.

b. Ethanol — 3 ml.

c. Dextrose — 10 g.

d. Sodium tauroglycocholate, 10% solution — 1 ml.

e. Distilled water — 96 ml.

Procedure

Mix 1.5 g of gum tragacanth with 3 ml of ethanol, 10 g of dextrose, 1 ml of 10% sodium tauroglycocholate and 96 ml of distilled water

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Autoclave at 10 psig for 10 min and cool

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To this add 25 g of the oily material under test and shake well — the book prints “25 ¢g”, carried as 25 g

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Make dilutions for examination from this in warm diluent

Precautions

• Cool the emulsifying diluent before adding the oily material.
• Shake well — the examination result depends on a uniform emulsion.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.