The effects of quality changes in vegetable oils on the formation and absorption of monochloropropanediol esters (MCPDE) and glycidyl esters (GE) during deep-frying of potato chips

Monochloropropanediol esters (MCPDE) and glycidyl esters (GE) are probably carcinogenic compounds found in refined vegetable oils and deep-fried foods. However, there was a lack of studies on the absorption of MCPDE and GE by food system fried with different types of oils. In this study, four major types of vegetable oils, i.e. palm olein (PO), canola (CNL), soybean (SBO), and sunflower oils (SFO) were used to fry potato chips for 40 cycles. The potatoes were pre-soaked in 5% NaCl before frying. The 3-MCPDE contents in soft oils (CNL, SBO, SFO) were found to increase across the frying cycles owing to the release of unsaturated FFA (lower pKa value) which was likely to dissociate and increase the acidity of the oil. In contrast, the 3-MCPDE content in PO decreased with frying cycles since saturated FFA (higher pKa value) has a less tendency to dissociate. After 40 frying cycles, the 3-MCPDE content in potato chips fried with PO (0.14 μg/g of chips) was found to be lower than CNL (0.25 μg/g of chips) and SBO (0.17 μg/g of chips), but slightly higher than SFO (0.12 μg/g of chips). On the other hand, the initial GE content in PO was found to be significantly higher (3.49 μg/g of oil) than the soft oils (≤0.1 μg/g). The GE content in potato chips did not change significantly across the frying cycles regardless of the vegetable oil used. In conclusion, the physicochemical properties of vegetable oil have been found to influence the 3-MCPDE level in fried food and it is critical to produce frying oil with low initial levels of contaminants (especially GE) to improve food safety.