SOP: Thiobarbituric Acid (TBA) Test for Rancidity

GIFSQ — Global Institute for Food Safety & Quality

Principle

The oxidation of fats produces compounds that react with 2-thiobarbituric acid to give red-coloured products. The fat sample is dissolved in an organic solvent such as benzene, chloroform or carbon tetrachloride, and the reactive material is extracted with an acetic acid–thiobarbituric acid–water solution. The aqueous extract, on heating, develops a red colour in the presence of oxidised fats.

Apparatus required

• Separating funnel
• Test tube
• Boiling water bath
• Steam bath (for preparing the TBA reagent)
• 100 ml volumetric flask

Reagents

a. TBA reagent: dissolve 0.67 g of thiobarbituric acid in distilled water on a steam bath; transfer the solution to a 100 ml volumetric flask, cool and make up to volume; mix an equal volume of this TBA solution with an equal volume of glacial acetic acid.

b. Carbon tetrachloride, CP grade.

Procedure

Dissolve an aliquot of the melted fat sample in 10 ml of carbon tetrachloride

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Add 10 ml of TBA reagent; shake thoroughly for 4 min

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Transfer the contents to a separating funnel and withdraw the aqueous layer into a test tube

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Immerse the tube in a boiling water bath for 30 min; cool and note the colour — a pink to red colour is formed depending upon the extent of oxidation

References

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