SOP: Identification of Beet Dye (Betanin) in Tomato Products

GIFSQ — Global Institute for Food Safety & Quality

Principle

Beet juice or betanin added to tomato products (tomato sauce, puree, ketchup) is distinguished from the normal tomato pigment by solubility: the normal tomato colouring matter is extracted with amyl alcohol, while betanin stays in the aqueous solution and can be dyed on tannin-mordanted cotton, giving a terracotta shade.

Apparatus required

• Separating vessel
• Piece of tannin-mordanted cotton

Reagents

a. Amyl alcohol.

b. Tannin-mordanted cotton.

Procedure

Prepare an aqueous suspension or solution of the tomato product

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Extract the normal tomato colouring matter with amyl alcohol — the betanin remains in the aqueous solution

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Put a piece of tannin-mordanted cotton into the aqueous solution and dye the betanin on the cotton

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A terracotta shade is produced, identifying the added beet dye

References

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