Elimination of 3-MCPD fatty acid esters and glycidyl esters during palm oil hydrogenation and wet fractionation

Abstract

Palm oil is the vegetable oil refined and modified in the largest amount. In this study, we present the effect of wet fractionation and hydrogenation of RBD palm oil on the removal of 3-MCPD and glycidyl esters. Fractionated palmstearins had significantly decreased contents of 3-MCPD esters (71–74%) and glycidyl esters (21–26%), whereas top olein contained the highest levels of processing-induced contaminants accompanied by polar compounds. Exhaustive hydrogenation conditions caused rapid degradation of 3-MCPD esters (51–70%) in high melting palm oil products. Reduction of glycidyl esters (1–42%) was dependent on the type of nickel catalyst. The effect of iodine value drop on the contaminant degradation was shown to be linear. The combined action of dry-reduced, supported, 22% Ni and Raney nickel catalysts was found to be an optimal. Adsorptive bleaching and deodorization of hydrogenated palm stearin impacted particularly repeated formation of glycidyl esters up to 1.01–1.76 mg/kg, while 3-MCPD esters remained under the input RBD palm oil level. The mechanism of the catalyst action was investigated with glycidyl-d5 palmitate, 3-MCPD-d5-1,2-dipalmitate. They were transformed into non-carcinogenic and non-genotoxic products by hydrogenolysis and deoxygenation reactions.