Tags : FSSAI

Determination of Volatile Oil

Method No. FSSAI 10.013:2021

Scope

This method specifies the determination of volatile oil content of most spices and condiments.

Caution

See Material Safety Data Sheets, or equivalent, for each reagent. Xylene is a flammable liquid, hazardous in case of skin or eye contact (irritant), ingestion, and inhalation.

Principle

The determination of volatile oil in a spice is made by distilling the spice with water, collecting the distillate in a graduated tube in which the aqueous portion of the distillate is automatically separated and returned to the distilling flask, and measuring the volume of the oil. The content of volatile oil is expressed as % v/w.

Apparatus/Instruments

1. Volatile oil trap, Clevenger type (lighter than water or heavier than water)
2. Flask, distilling, 1000 mL, preferably with magnetic stirrer
3. Heating source: Oil bath/ heating mantle/ stirring hotplate
4. Glass beads, if stirring hotplate is not used

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Materials and Reagents

• Xylene (Reagent grade)
• Sodium chloride (NaCl) solution: 10% (w/v)
• Cleaning solutions:
  • Acetone (for fatty residues)
  • Chromic-sulphuric acid mixture
  • Liquid glassware cleaner
• Antifoam (preferably Antifoam B)

Method of Analysis

1. Grind the sample to pass through No. 20 (850 micron) sieve. Regrind oversize until the test portion passes the sieve.
2. Weigh accurately 20 – 50 g of the spice enough to yield 2 - 4 mL of oil if possible.
3. Place in the flask with glass beads or porous earthenware pieces, if a magnetic stirrer is not used.
4. Add about 300 mL water and a drop of antifoam if necessary.
5. Fill the trap with water.
6. Place an efficient water-cooled condenser on top of the trap and heat the flask with good stirring or agitation until boiling starts and continue boiling moderately briskly, but so that the lower part of the condenser remains cold.
7. Set the apparatus so that the condensate will not drop directly on the surface of the liquid in the trap but run down the sidewalls.
8. Rotate the flask occasionally to wash down any material adhering to the upper part of the walls.
9. Distill until two consecutive readings taken at 1 h intervals show no change in oil content (more than 6 h).
10. Remove the source of heat and read the volume of oil ten minutes or so later. Calculate as v/w and express the results in %.
11. If the oil separates in the graduated portion of the trap or clings to the walls, add several drops of a saturated aqueous detergent solution through the top of the condenser. Repeat if necessary. Distill for at least 10 min after adding detergent to wash out the trap.

Note

• Some oils (e.g., Cassia) have a density close to 1 or separate into two fractions in the trap (allspice, nutmeg). For these, prior to adding the sample to the flask, add 1.0 mL xylene to the trap and distill without the sample for at least half an hour. Cool and read the volume of xylene after 2 minutes. Add the sample and distill for up to six hours as before. Subtract the volume of xylene from the total volume of the organic layer in the trap. Calculate as before.
• The oil obtained (without the use of xylene) may be recovered, dried with a small amount of sodium sulfate, and its characteristics such as density and refractive index can be determined.

Calculation

Calculate volatile content % (v/w) in the test portion as:
$Volatileoil(\mathrm{\%}v/w)=\left(\frac{V}{W}\right)\times 100$

Where:

• ( V ) = Volume of oil collected in the trap (mL)
• ( W ) = Mass of the test portion (g)

Note

The results should be reported on a dry basis by multiplying the value obtained with:
$\frac{100\mathrm{\%}}{100\mathrm{\%}-M}$

Where:

• M = Moisture content of sample as received, in %

Reference

1. FAO Manual of Food Quality Control (1986)14 / 8 page 239
2. AOAC 17th edn., 2000 Official Method 962.17
3. IS 1797 : 2017, Spices and Condiments- Methods of Test (Third revision)