Preparation of fatty acid methyl esters from olive oil and other vegetable oils using aqueous hydrochloric acid-methanol

Abstract

Fatty acid methyl ster analysis is used for the examination of olive oil adulteration. Because of the toxicity of boron trifluoride-methanol reagent, which is currently used for the esterification of fatty acids, the use of aqueous hydrochloric acid-methanol as an esterification reagent has been studed. The method involves hydrolysis of lipids with a 2% sodium hydroxide in methanol solution, followed by esterification with aqueous hydrochloric acid in methanol (3 + 2) for 10 min on a steam-bath. A detailed study of the esterification of olive oil and of other vegetable oils with a high content of unsaturated fatty acids has been undertaken. Comparison of this esterification with that using boron trifluoride and hydrochloric acid has given excellent agreement of results. Methyl ester hydrolysis has been found to take place during the esterification step. The hydrolysis does not affect the reliability of the method.