SOP: Essential Oil Content in Lemon and Orange Extracts

GIFSQ — Global Institute for Food Safety & Quality

Principle

The essential oil is liberated from the extract with dilute hydrochloric acid and warm water, and separated by centrifuging in a Babcock milk test bottle; the oil volume is read off the graduated neck with a correction for the solubility of the oil, and converted to per cent by weight using the density factors for lemon and orange extracts.

Apparatus required

• Babcock milk test bottle
• Water bath (60 °C)
• Centrifuge

Reagents

a. HCl (1 + 1).

Procedure

Pipette 20 ml of the sample into a Babcock milk test bottle

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Add 1 ml of HCl (1 + 1) and 25–28 ml of water heated to 60 °C, mix, and incubate in a water bath at 60 °C for 5 min

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Centrifuge for 5 min and fill the bottle with warm water to bring the oil to the graduated neck of the flask

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Again centrifuge for 2 min, and incubate the flask at 60 °C for a few minutes

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Note the per cent oil by volume

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If the oil content is more than 2%, add 0.4% to the per cent oil noted to correct for the solubility of the oil; if the oil content is less than 2% but more than 1%, add 0.3% for the correction

Calculation

% oil by weight = (% oil by volume × 0.86) / specific gravity of the original extract (lemon extracts)

% oil by weight = (% oil by volume × 0.85) / specific gravity of the original extract (orange extracts)

Where,

• % oil by volume = per cent oil read off the Babcock bottle, with the solubility correction added

Oil content in lemon and orange flavours could also be estimated by polarization; if the base used in such preparations is oil, the oil content can be determined by steam distillation — procedures for these methods are given in the AOAC.

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, 1975, 12th edn., p. 328.