Determination of mono- and di-acylglycerols in milk lipids

Abstract

A simple and rapid method based on solid phase extraction and gas chromatography has been developed for the determination of monoacylglycerols (MAG) and diacylglycerols (DAG) at low-concentration levels typically found in milk and dairy ingredients. The method enabled measurement of individual milk MAG (including isomeric forms) with the exception of glycerol, monobutyrate. The DAG were separated and quantified as groups according to their carbon numbers. However, it was possible to identify the major DAG components within a group. The minimum detection limits for MAG and DAG were in the range of 5–8 and 10–17 μg/ml, respectively. The corresponding R.S.D. values were 1.7–3.9 and 0.2–9.9%, respectively. C8–C18 MAG and C26–C36 DAG were present in the lipids extracted from whole milk, anhydrous milk fat and buttermilk. The concentrations of MAG and DAG in buttermilk were, respectively, thirteen- and three-folds higher than that in whole milk or anhydrous milk fat. In dairy lipids, 1,2(2,3)-DAG isomers predominated almost to the exclusion of 1,3-isomers.