SOP: Detection of Argemone Seeds in Mustard Seeds and Powder

GIFSQ — Global Institute for Food Safety & Quality

Principle

Argemone oil present as an adulterant in mustard oil gives an orange-red precipitate in light flocks in the acid layer when treated with hydrochloric acid and ferric chloride reagent; under the microscope the precipitate appears as needle-like crystals (straight for argemone; curved needles suggest a drying oil like linseed or safflower instead).

Apparatus required

• 250 ml conical flask
• Whatman No. 1 filter paper
• Test tube
• Boiling water bath

Reagents

a. Ethyl ether.

b. Ferric chloride reagent: dissolve 10 g of crystalline ferric chloride in 10 ml of concentrated HCl and dilute to 100 ml with water; filter the solution if hazy.

c. Concentrated HCl: 2.0 ml per test.

d. Rectified spirit: 0.4 ml per test.

Procedure

To 50 g of the sample in a 250 ml conical flask, add 125 ml of ethyl ether, and store overnight with occasional shaking

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Filter the ether extract through Whatman No. 1 filter paper, and wash the residue twice with 50 ml portions of ether

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Evaporate the combined ether extract and dry the residual oil at 100 ± 1 °C until free from moisture

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Filter the residual oil

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Pipette 5 ml of the oil into a test tube, add 2.0 ml of concentrated HCl and 0.4 ml of rectified spirit, and mix thoroughly

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Place the tube in a boiling water bath for 2 min, when the acid and the oil layers separate

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Take out the tube from the bath and add slowly from the side, 1 ml of ferric chloride reagent

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Roll the tube gently between the palms to ensure mixing — do not shake the tube

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Place the tube again in the boiling water bath for 12 min and examine

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Formation of orange-red precipitate in light flocks in the acid layer indicates the presence of argemone seeds — under the microscope, the precipitate appears as small or large needle-like crystals; if the needles are curved instead of straight, it may indicate the presence of a drying oil like linseed or safflower along with mustard oil

References

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