สารบัญ

Olive Oil.

Thai name  น้ำมันมะกอก (NAM MAN MAKOK)

Category  Pharmaceutic aid.

Virgin Olive Oil is the fixed oil obtained from cold expression or other suitable mechanical means from the ripe drupes of Olea europaea L. (Family Oleaceae).

Origin of plant  Virgin Olive Oil-yielding plant is native to Africa, Mediterranean, and South-Central China.

Constituents  Virgin Olive Oil contains mainly triglycerols and fatty acids, predominantly oleic, palmitic, linoleic acids.  Other components are -tocopherol, campesterol, and phenolic compounds.

Description  Clear, transparent, yellow or greenish yellow liquid; odour, mild, characteristic, and not rancid.

Solubility  Practically insoluble in ethanol, miscible with petroleum ether (boiling range, 50° to 70°). When cooled, it begins to become cloudy at 10° and becomes a butter-like mass at about 0°.

Packaging and storage  Virgin Olive Oil shall be kept in well-filled, tightly closed containers, protected from light, and stored at a temperature not exceeding 25º.

Identification of fixed oils by thin-layer chromatography  Carry out the test as described in Appendix =.

      Results  The chromatogram obtained is similar to the corresponding chromatogram shown in the figure.

Water  Not more than 0.1 per cent w/w (Karl Fischer Method, Appendix 4.12); use 1 g.

Light absorption  The absorbance of a 1.0 per cent w/v solution in cyclohexane, determined at the maximum at about 270 nm, is not more than 0.20. The ratio of the absorbance at 232 nm to that at 270 nm is more than 8 (Appendix 2.2). 

Acid value  Not more than 2.0 (Appendix 5.4), use 5.0 g.

Peroxide value  Not more than 20.0 (Appendix 5.12).

Unsaponifiable matter  Not more than 1.5 per cent w/w (Method II, Appendix 5.8); use 5.0 g.

Composition of fatty acids  Carry out the test as described in the “Gas Chromatography” (Appendix 3.4).

Standard solution  Prepare an ester mixture of known composition containing the esters required in the Virgin Olive Oil. (Nu-Chek mixture 17A^® or equivalent is suitable.)

0.5 M Methanolic sodium hydroxide solution  Dissolve 2 g of sodium hydroxide in 100 mL of methanol.

Test solution  (Note  If fatty acids containing more than 2 double bonds are present in the sample, remove air from the flask by purging it with nitrogen for a few minutes.) Transfer about 100 mg of the sample, accurately weighed, to a 50-mL conical flask fitted with a suitable water-cooled reflux condenser and a magnetic stir bar. Add 4 mL of 0.5 M Methanolic sodium hydroxide solution, and reflux until fat globules disappear (usually 5 to 10 minutes). Add 5.0 mL of a solution prepared by dissolving 14 g of boron trifluoride in methanol to make 100 mL, swirl to mix, and reflux for 2 minutes. Add 4 mL of n-heptane for chromatography through the condenser, and reflux for 1 minute. Cool, remove the condenser, add about 15 mL of a saturated solution of sodium chloride, shake, and allow the layers to separate. Pass the n-heptane layer through 100 mg of anhydrous sodium sulfate (previously washed with n-heptane for chromatography) into a suitable flask. Transfer 1.0 mL of this solution to a 10-mL volumetric flask, dilute with n-heptane for chromatography to volume, and mix.

System suitability solution  Transfer about 20 mg each of stearic acid, palmitic acid, and oleic acid to a 25-mL conical flask fitted with a suitable water-cooled reflux condenser and a magnetic stir bar, and prepare as directed for Test solution beginning with “Add 5.0 mL of a solution prepared by dissolving . . . .”

Chromatographic system

Detector  Flame ionization.

Column  A fused-silica capillary column (30 m × 0.53 mm) bonded with a 1.0-µm layer of polyethylene glycol compound (Polyethylene Glycol Compound 20M^®, also know as Carbowax 20M^®, or equivalent.)

Temperature

Column The temperature programme is as follows:

                  Injection port 220.

                  Detector 260.

Carrier gas  Helium.

Flow rate  About 50 cm per second (6.6 mL per minute).

(Note  The relative retention times are about 0.87, 0.99, and 1.0 for methyl palmitate, methyl stearate, and methyl oleate, respectively.)

System suitability

Sample  System suitability solution

Suitability requirements

Resolution  Not less than 1.5 between methyl stearate and methyl oleate peaks.

Relative standard deviation  The relative standard deviation of the peak area responses for the palmitate and stearate peaks for replicate injections is not more than 6.0 per cent.  The relative standard deviation of the peak area response ratio of the palmitate to stearate peaks from these replicate injections is not more than 1.0 per cent.

Procedure  Separately inject equal volumes (about 1 µL) of Standard solution and Test solution into the chromatograph, and record the chromatograms. Identify the peak due to the fatty acid ester peaks in the chromatogram of the Test solution by comparing the retention times of these peaks with those in the chromatogram of the Standard solution, and measure the peak areas for all of the fatty acid ester peaks in the chromatogram from the Test solution.

Calculation  Calculate the percentage content of the components of Virgin Olive Oil taken by normalization procedure. 

Limits  Virgin Olive Oil exhibits the composition profiles of fatty acids in Table 1 below.

 Table 1

Sesame oil  In a ground-glass-stoppered cylinder, shake 10 mL for about 1 minute with a mixture of 0.5 mL of a 0.35 per cent V/V solution of furfural in acetic anhydride and 4.5 mL of acetic anhydride. Filter through a filter paper impregnated with acetic anhydride. To the filtrate add 0.2 mL of sulfuric acid. No bluish green colour develops.