Effects of fatty acids found in diacylglycerols and monoacylglycerols on the formation of 3-monochloropropane-1,2-diol esters and glycidyl esters during heating

3-Monochloropropane-1,2-diol (3-MCPD) esters and glycidyl esters (GEs) are contaminants commonly found in refined edible oils. Although diacylglycerols (DAGs) and monoacylglycerols (MAGs) are known precursors of these compounds, the influence of esterified fatty acids on their formation remains unclear. This study employed a stable isotope tracer approach to systematically investigate the formation of 3-MCPD esters and GEs from DAGs and MAGs containing six fatty acids: lauric, palmitic, stearic, oleic, linoleic, and α-linolenic acid. Deuterium-labeled DAG or MAG was spiked into palm oil, with or without chloride, and then heated at 230, 250, or 270 °C. The resulting deuterium-labeled contaminants were quantified by LC–MS/MS. The formation of GEs and 3-MCPD esters from DAGs was consistently higher than that from MAGs under all conditions. Chloride addition significantly promoted the formation of 3-MCPD diesters and GEs. DAGs containing linoleic acid yielded the highest levels of GEs and 3-MCPD diesters, while those containing α-linolenic acid had lower yields, likely due to thermal degradation. Altogether, the types of partial acylglycerol and esterified fatty acids critically determine the contaminant formation. Therefore, reducing the DAG content and limiting chloride exposure, particularly in oils rich in unsaturated fatty acids, may serve as effective mitigation strategies during edible oil refining. • Formation of 3-monochloropropane-1,2-diol (3-MCPD) esters and glycidyl esters (GEs) was traced using deuterium-labeled precursors. • Diacylglycerols (DAGs) generated more 3-MCPD esters and GEs than monoacylglycerols (MAGs) under all heating conditions. • DAGs containing linoleic acid strongly promoted the formation of 3-MCPD diesters and GEs. • DAGs containing α-linolenic acid reduced the formation of 3-MCPD diesters and GEs due to thermal degradation. • Fatty acid type and chloride level significantly influenced the formation of 3-MCPD esters and GEs.