SOP: Detection of Turmeric by the Boric Acid Test

GIFSQ — Global Institute for Food Safety & Quality

Principle

The colouring agent in turmeric is curcumin. Dried filter paper impregnated with the material’s alcoholic extract gives a cherry-red colour with a weak solution of boric acid in the presence of HCl, which changes to bluish green on addition of NaOH or NH₄OH.

Apparatus required

• Water bath
• Filter paper

Reagents

a. Alcohol (for extraction).

b. A weak solution of boric acid, to which a few drops of HCl have been added.

c. NaOH or NH₄OH solution.

Procedure

Evaporate an alcoholic extract of the material almost to dryness on the water bath with a piece of filter paper

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Moisten the dried paper with a few drops of the weak boric acid solution containing HCl

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Dry the paper again — if turmeric is present, the dried paper will be of cherry-red colour

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Add a drop of NaOH or NH₄OH — the cherry-red colour is changed to bluish green

References

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