SOP: Oil Content in Spice Extracts

GIFSQ — Global Institute for Food Safety & Quality

Principle

Spice extracts carry the flavouring constituents of the natural spice in a solvent such as propylene glycol or vegetable oil. The original solvent is removed where possible, the oil is liberated into a salt solution and separated by centrifuging in a Babcock milk test bottle; the oil column is read off the graduated neck, with a correction for the oil retained in the solvent mixture.

Apparatus required

• Babcock milk test bottles
• Centrifuge which can take the milk test bottles
• Small glass tube (for blowing air into the bottle)

Reagents

a. Solvent mixture: equal parts of USP mineral oil and moisture-free kerosene mixed in the ratio of 1:1.

b. Saturated magnesium sulphate solution.

c. Saturated NaCl solution.

d. Dilute HCl (1 + 1).

Procedure

Cassia, cinnamon and clove extracts:

Pipette 10 ml of the sample into a Babcock milk test bottle

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Blow air into the bottle through a small glass tube for 30 min or longer to remove most of the alcohol present

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Add 1 ml of the solvent mixture and shake well

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Fill the bottle with saturated magnesium sulphate solution

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Centrifuge for 10 min and read the volume of oil from the extreme bottom to the extreme top of the column

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To obtain the oil content as per cent, subtract 5 divisions and multiply the remainder by 2

Anise and nutmeg extracts:

Take 10 ml of the sample in a Babcock milk test bottle

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Add 1 ml of HCl (1 + 1); dilute the saturated NaCl solution with water (1 + 1), heat to 60 °C, fill into the Babcock test bottle up to the neck, and stopper the bottle

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Incubate in a water bath at 60 °C for 15 min, rotating occasionally, and centrifuge for 10 min at 800 rpm

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Fill the bottle to the neck with saturated NaCl solution and again centrifuge for 10 min; if separation is not clear, cool to 10 °C and centrifuge again for 10 min

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Note the reading and multiply by 2 to get the per cent oil content by volume

Peppermint, spearmint, wintergreen and other spice extracts:

Pipette 10 ml of the sample (or 5 ml when the oil content is more than 5% by volume) into a Babcock milk test bottle

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Add 0.5 ml of solvent mixture, 1 ml of HCl (1 + 1), and fill to the shoulder with saturated NaCl solution

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Shake the bottle for 3 min and add NaCl solution to bring the column of oil within the graduations of the neck

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Centrifuge for 10 min at high speed, and read the volume of oil from the extreme bottom to the extreme top of the column — in the case of peppermint and pimento extracts, read from the extreme bottom to the bottom of the meniscus at the top of the column

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Calculate the percentage of oil by subtracting 2.5 divisions and multiplying the remainder by 2 — if 5 ml of the sample has been used, multiply by 4

References

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

Official Methods of Analysis, Association of Official Analytical Chemists, Washington DC, 12th edn., p. 343, 344 (1975).