Determination of hydroxyl value in fats and oils using an acid catalyst

Abstract

A method for the rapid determination of the hydroxyl value of oils, fats and related products is described. The method uses toluene-p-sulphonic acid as a catalyst and this allows the sample, dissolved in toluene, to be acetylated in 10 min at room temperature. The fatty acid anhydrides formed during the acetylation are decomposed with aqueous sodium hydroxide and tert-butanol, and are then titrated with hydrochloric acid. The addition of an aliquot of the sample to the blank after the decomposition of the acetic anhydride reduces the number of titrations required to two.