3-Monochloropropanediol (3-MCPD) and related esters are process contaminants formed during vegetable oil refining. They form from the reaction of acylglycerols in the presence of chlorine and high temperature during deodorization, and this is supported by a significant positive correlation of 3-MCPD esters with total chlorine content in oil prior to refining. However, the specific chlorine sources most responsible for the formation of 3-MCPD esters are not well understood. We investigated the various chloride sources present in vegetable oils, and in particular palm oils and identified organochlorines as the most important for 3-MCPD ester formation. Characteristic chlorine isotope mass patterns (defect and ratio) exhibited in high-resolution mass spectrometry analysis of vegetable oils was used to identify organochlorine compounds. Organochlorine compounds present in all vegetable oils (soybean, rapeseed, sunflower, coconut, olive, oil palm, and corn) were evaluated and identified as wax ester, fatty acid, diacylglycerol and sphingolipid derivatives produced in fruit along with lipid biosynthesis. Our study identified organochlorine sphingolipid compounds as the main precursors of 3-MCPD esters, showing a reduction after deodorization process and higher 3-MCPD esters formed after enrichment using silica column chromatography and dosing of oil samples before refining. Subsequently, LC-MS/MS and NMR techniques were adopted in order to elucidate and confirm the structures of these important precursors. Changes of sphingolipid organochlorine composition during oil palm fruit processing and oil refining was also investigated to provide insight into the mechanism of precursor formation and their conversion to 3-MCPD esters. The role that lipase enzymes play in these processes will also be discussed.

Organochlorines as the most significant precursors of 3-MCPD esters in Palm Oil: Investigation into their occurrence in a range of vegetable oils, structures and mechanism of formation

256th National Meeting (2018)

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