Formation of Glycidyl Esters during Processes of Interesterified Edible Oil Products

Glycidyl esters (GEs) are process contaminants mainly formed during the deodorization step in the refining process of edible oils. The toxicological concern of GEs is based on GEs hydrolysis into the free form glycidol in the gastrointestinal tract. Glycidol is a genotoxic carcinogen, which has already been classified as group 2A by the International Agency for Research on Cancer (IARC). According to the previous studies, diacylglycerols (DGs) and monoacylglycerols (MGs) are precursors of GEs and the presence of them could therefore significantly increase the yield of GEs during processing. Generally, processing steps of interesterification products include oil blending, chemical/enzymatic interesterification, and the following deodorization step. As a result, the formation of GEs in the deodorization process could be of great concern in view of high DGs contents in the interesterification products. The objective of this project is to study the formation and changes of GEs during interesterification and deodorization processes. This research proposal is planned to be a two-year project. In the first year, a novel matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) method will be developed for direct analysis of individual glycidyl ester of fatty acids in edible oils. The matrix and solvent will be further selected, and the validation study of this method will be performed to demonstrate that the method is suitable and reliable for GEs determination. The content and composition of GEs in commercial refined edible oil products will be analyzed by the validated method. In the second year, a model system will be built to evaluate the GEs formation during laboratory-scale processes of chemical/enzymatic interesterification and deodorization. The refined oil feedstocks will be first removed their endogenous GEs and then be blended at the predetermined ratios with or without (as control) spiking glycidyl stearate. The chemical and enzymatic interesterification will be carried out under default conditions for the oil blends. After interesterification, the GEs content and composition in products will be analyzed by the MALDI-TOF-MS method, along with the triacylglycerol profile analysis, lipid classes analysis, and acid value determination. In addition, the impacts of water content and reaction time on enzymatic interesterification reaction will be studied. Second, the interesterification products will be exposed to high temperature under vacuum simulating deodorization step and analyzed their GEs contents thereafter to correlate with the DGs and MGs contents in the reactant oil. Through this project, it is expected to elucidate the formation mechanism during interesterification processes and make contributions toward the national and global food safety issue of GEs in oil products.