Formation Behavior of 3-MCPD Esters and Glycidyl Esters from Diacylglycerols during Oil Deodorization: Insights from Stable Isotope Tracing

Abstract 3-Monochloropropane-1,2-diol esters (3-MCPDE) and glycidyl esters (GE) are undesirable process contaminants formed during edible oil deodorization, with diacylglycerols (DAG) recognized as important precursors. This study investigated how the fatty acid composition of DAG influences the formation of 3-MCPDE and GE under industrially relevant deodorization conditions using stable isotope-labeled DAGs. Palm oil containing deuterium-labeled DAGs was deodorized at 250 °C for 60 min with or without chloride addition, and labeled 3-MCPDE, GE, DAG, and monoacylglycerols (MAG) were quantified by LC–MS/MS. Chloride significantly enhanced the formation of both 3-MCPDE and GE. DAG species containing unsaturated fatty acids, particularly oleic and linoleic acids, generated substantially higher levels of both contaminants than did saturated DAG species. Corresponding decreases in labeled DAG and increases in MAG supported preferential conversion of unsaturated DAGs during deodorization. These findings provide direct experimental evidence that the fatty acid composition of DAG strongly influences the formation of 3-MCPDE and GE during oil deodorization.