Abstract: monochloropropanediol esters (MCPDEs) and glycidyl esters (GEs) have attracted increasing attention as potential process contaminants generated during thermal food processing. However, their formation patterns during traditional Chinese cooking and reheating remain unclear. In this study, a typical Chinese dish, stir-fried pork with green peppers, was selected as a model system to systematically investigate the effects of cooking temperature, heating time, and salt (dosage, type, and addition timing) on the formation of MCPDEs and GEs. Furthermore, the impacts of different reheating methods (stir-frying and microwave reheating) were evaluated. The results indicated that high temperatures and high salt concentrations significantly accelerated the accumulation of MCPDEs and GEs in the oil phase. Cooking at 190 ℃ for 4 min elevated the concentrations of 3-MCPDE, 2-MCPDE and GEs to 1.11, 0.41, and 1.08 mg/kg, respectively. The concentrations of target contaminants generally rose with increasing NaCl dosage. The levels of MCPDEs and GEs displayed divergent trends upon prolonged heating: 3-MCPDE peaked at 1.05 mg/kg at 5 min and dropped to 0.99 mg/kg at 6 min, while GEs continuously increased and reached 1.04 mg/kg at 6 min. Relative to early salt addition, adding salt right before serving lowered the concentrations of 3-MCPDE, 2-MCPDE and GEs to 0.82, 0.27, and 0.76 mg/kg, with reduction percentages of 34.4%, 25.0%, and 32.1%. Stir-frying at 190 ℃ for 9 min resulted in GE levels of 1.88 mg/kg, roughly 1.66 times as high as the value obtained by high-power microwave reheating, suggesting that microwave reheating mitigated the secondary accumulation of these hazardous esters. This study elucidates the impact of thermal load and chloride ions on the formation of harmful esters in Chinese cuisine. Building on this, we propose a strategy of “moderate temperature control, late seasoning, and microwave reheating”, providing both theoretical insights and practical guidance for reducing food safety risks associated with thermal processing.

Key words: chloropropanol esters; glycidyl esters; Chinese cooking; reheating methods