The impact of fat deterioration on formation of acrylamide in fried foods

Abstract: Food safety studies on acrylamide are mainly focused on the food material (potential precursors), storage and processing conditions, and analytical methods neglecting the impacts of changing physical and chemical properties of the frying medium. The influence of the type of frying oil used and subsequent frying processes on acrylamide formation is a matter of controversial debate.

The frying tests led to the assumption that oil type has no direct impact but the thermal stress may have an effect on the mechanism of acrylamide formation. This current study examines the extent to which thermal degradation reaction products directly affect acrylamide formation in fried foods, particularly French-fries. The successive frying tests at 170 °C and 180 °C were carried out with rapeseed oil for 32 hrs with 128 frying cycles. The acrylamide content in French fries was determined by LC-MS/MS. The thermo-oxidation process has been monitored using different chemical parameters to follow the oxidative and thermal degradation, namely, total polar compounds, di- and polymerised triacylglycerols, monomer oxidised triacylglycerols, p-anisidine value, mono and di-acylglycerols, acid value, epoxy fatty acids, iodine value, saponification value and fatty acid composition.

During long term successive frying, the nature of the frying medium and its degradation level have a direct impact on the formation of acrylamide. It was surprising to see that the formation of acrylamide is substantially reduced when the acid value exceeded 0.5 mg KOH/g. Lowering the pH inhibits Schiff-base formation by favoring protonation of the amine group of asparagine.