SOP: Detection of Annatto in Foods

GIFSQ — Global Institute for Food Safety & Quality

Principle

The colouring matter in annatto is bixin. Filter paper moistened with an alkaline extract of the material shows a straw colour that resists washing; on treatment with stannous chloride and drying, the colour turns purple, confirming annatto.

Apparatus required

• Filter paper

Reagents

a. Warm 2% NaOH solution (for shaking out oil or melted, filtered fat).

b. 40% stannous chloride solution.

Procedure

Shake out oil or melted and filtered fat with warm 2% NaOH solution to obtain an alkaline solution of the material

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Pour the alkaline solution on moistened filter paper

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If annatto is present, the filter paper will show a straw colour, which will remain even with a gentle stream of water

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Dry the filter paper, add a drop of 40% stannous chloride solution, and dry carefully again

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If the colour turns purple, the presence of annatto is confirmed

References

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