Density functional theory study of the mechanism for the formation of glycidyl esters from triglyceride

Abstract

Glycidyl fatty acid esters (GEs) are by-products of edible oil refinement that have attracted attention globally due to concerns over their possible harmful effects on human health when consumed. It is thus important to improve our understanding of GE formation if we are to suppress GE production during edible oil refinement. In this paper, a first-principles density functional theory study of the formation mechanism of GEs was performed. Triglycerides undergo a self-condensation reaction between two adjacent ester groups to yield GEs and an anhydride as a by-product. This process is energetically unfavorable, having a relatively high activation energy of around 80 kcal/mol, which indicates that GE formation is intrinsically a high-temperature process. Both the thermodynamic and the kinetic energies of the reaction are insensitive to the size of the fatty chain substituents present. If water participates in the self-condensation, the activation barrier is notably decreased by 23.9 kcal/mol, indicating that GE production in the presence of high-temperature water vapor should be more kinetically favorable. Our results suggest that reducing the reaction temperature and avoiding the use of water should suppress GE production during edible oil refinement.