Dynamic changes of 3-MCPD esters and glycidyl esters contents as well as oil quality during repeated deep-frying

In this study, the dynamic changes of 3-monochloropropane-1,2-diol esters (3-MCPDEs) and glycidyl esters (GEs) in both oils and French fries were assessed using headspace-solid phase microextraction-gas chromatography-mass spectrometry over the course of 5 days repeated deep-frying. The color parameter, as well as the concentrations of tocopherols and total polar components (TPC) in frying oils, were also evaluated. The content of 3-MCPDEs in frying oil reduced by 71.2% in the first two days of frying while GEs increased steadily. The concentration of 3-MCPDEs in French fries increased over the repeated frying while GEs and oil uptake maintained constant. The concentration of tocopherols decreased while TPC increased significantly during repeated deep-frying. Microstructure analysis of French fries by X-ray micro-computed tomography (micro-CT) indicated the reduction of micropores and the appearance of bigger oil-filled macropores, which might be responsible for the enrichment effect of French fries on 3-MCPDEs and GEs. This research broadens the understanding of the fate of 3-MCPDEs and GEs in repeated deep-frying.