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SOP: Alcohol Extract in Spices

GIFSQ — Global Institute for Food Safety & Quality

Principle

The alcohol-soluble matter is extracted by steeping the sample in 95% ethyl alcohol for 16 hr; an aliquot of the filtered extract is evaporated to dryness and the residue weighed, giving the alcohol extract as a percentage of the sample weight. Spices containing more than 5% volatile oil are extracted in a Soxhlet apparatus with 90% alcohol instead.

Apparatus required

  • 250 ml glass-stoppered conical flask
  • Whatman No. 2 filter paper
  • Flat-bottomed evaporating dish
  • Water bath
  • Hot air oven
  • Soxhlet apparatus (for spices containing more than 5% volatile oil)

Reagents

a. 95% ethyl alcohol (90% alcohol for the Soxhlet extraction of spices containing more than 5% volatile oil).

Procedure

Weigh 2.0 g of the prepared sample and transfer to a 250 ml glass-stoppered conical flask

↓

Add 100 ml of 95% ethyl alcohol, stopper, and mix by swirling

↓

Store overnight or 16 hr at room temperature

↓

Filter the extract through a dry Whatman No. 2 filter paper; discard the first 10 ml of the filtrate

↓

Pipette 50 ml of the filtrate into a flat-bottomed evaporating dish, evaporate to dryness on a water bath, and dry in a hot air oven at 110 ± 2 °C (105 ± 1 °C according to the Manual of Methods of Tests and Analysis of Foods, Govt. of India) until the difference between two consecutive weighings taken at 30 min intervals is not more than 1 mg

↓

Weigh the residue — the weight of the residue is the alcohol extract

↓

For spices containing more than 5% volatile oil, carry out the extraction in a Soxhlet apparatus using 90% alcohol

Calculation

Alcohol extract % = ((Wt of residue × 2) × 100) / Wt of sample

Where,

  • Wt of residue = weight of the residue obtained from 50 ml of the filtrate (half of the 100 ml extract; multiplied by 2 for the total extract)
  • Wt of sample = weight of the sample taken

Note: the printed calculation fraction in the available copy reads “Wt of residue / Wt of sample × 100” without the aliquot factor; the factor 2 is required because the residue comes from 50 ml of the 100 ml extract.

References

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