Self-emulsifying Monostearin; Self-emulsifying Mono-and Diglycerides of Food Fatty Acids
Action and use
Excipient.
DEFINITION
Self-emulsifying Glyceryl Monostearate is a mixture consisting principally of mono-, di- and triglycerides of stearic and palmitic acids and of minor proportions of glycerides of other fatty acids; it may also contain free glycerol, free fatty acids and soap. It contains not less than 30.0% of monoglycerides, calculated as C21H42O4, not more than 7.0% of free glycerol, calculated as C3H8O3, and not more than 6.0% of soap, calculated as sodium oleate, C18H33NaO2, all calculated with reference to the anhydrous substance.
CHARACTERISTICS
A white to cream coloured, hard, waxy solid.
Dispersible in hot water; soluble in hot absolute ethanol, in hot liquid paraffin and, subject to turbidity at concentrations below 20%, in hot vegetable oils.
TESTS
Acid value
Not more than 6, Appendix X B.
Iodine value
Not more than 3 (iodine monochloride method), Appendix X E.
Alkalinity
Shake 1 g with 20 mL of hot carbon dioxide-free water and allow to cool with continuous shaking. The pH of the aqueous layer is 8.0 to 10.0, Appendix V L.
Water
Not more than 2.0% w/w, Appendix IX C. Use 0.5 g and a mixture of 10 mL of anhydrous methanol and 10 mL of anhydrous chloroform as the solvent.
ASSAY
For free glycerol
Dissolve 0.4 g in 50 mL of dichloromethane in a ground-glass-stoppered separating funnel, cool if necessary, add 25 mL of water and shake vigorously for 1 minute; add 0.2 mL of glacial acetic acid, if necessary, to break the emulsion. Repeat the extraction a further three times using 25-, 20- and 20- mL quantities of water and reserve the dichloromethane solution for
the Assay for monoglycerides. Filter the combined aqueous extracts through a filter paper moistened with water, wash the filter with two 5 mL quantities of water and dilute the combined filtrate and washings to 100 mL with water. To 50 mL of this solution add 25 mL of periodic acetic acid solution, shaking cautiously, allow to stand at 25° to 30° for 30 minutes and add 100 mL of water and 12 mL of potassium iodide solution. Titrate with 0.1M sodium thiosulfate VS using 1 mL of starch solution as indicator. Repeat the determination using 50 mL of water in place of the 50 mL of the solution being examined. The difference between the titrations represents the amount of sodium thiosulfate required. Each mL of 0.1M sodium thiosulfate VS is equivalent to 2.3 mg of glycerol.
For monoglycerides
Filter the reserved dichloromethane solution obtained in the Assay for free glycerol through absorbent cotton and wash the separating funnel and the filter with three 5 mL quantities of dichloromethane. Dilute the combined filtrate and washings to 100 mL with dichloromethane and to 50 mL of the solution add 25 mL of periodic acetic acid solution, shaking cautiously. Allow to stand at 25° to 30° for 30 minutes and add 100 mL of water and 12 mL of potassium iodide solution. Titrate the liberated iodine with 0.1M sodium thiosulfate VS using 1 mL of starch solution as indicator. Repeat the determination using 50 mL of dichloromethane in place of the 50 mL of the solution of the substance being examined. The difference between the titrations represents the amount of sodium thiosulfate required. Each mL of 0.1M sodium thiosulfate VS is equivalent to 17.9 mg of 1-monoacylglycerols, calculated as C21H42O4. The quantity of 0.1M sodium thiosulfate VS used in the assay is not less than 85% of the quantity of sodium thiosulfate used in the blank assay.
For soap
Add 10 g to a mixture of 60 mL of acetone and 0.15 mL of a 0.5% w/v solution of bromophenol blue in a mixture of 20 mL of ethanol (20%) and 80 mL of water, the solvent having been previously neutralised with 0.1M hydrochloric acid VS or 0.1 M sodium hydroxide VS. Warm gently on a water bath until solution is complete and titrate with 0.1M hydrochloric acid VS until the blue colour is discharged. Allow to stand for 20 minutes, warm until any solidified matter has redissolved and, if the blue colour reappears, continue the titration. Each mL of 0.1M hydrochloric acid VS is equivalent to 30.45 mg of C18H33NaO2
