Deep-frying improves digestibility and palatability of food. The aroma volatile compounds produced during frying include secondary oxidation products (SOPs) of fatty acids, such as saturated and unsaturated aldehydes. Release of these compounds may pose health hazards due to their toxic nature and be indicative of thermal degradation of oils. The emission profile of SOPs can depend on many parameters, including the type of oil, frying time and temperature, and the type of fried food. Precise determination of the emission pattern, however, requires adequate measurement tools that enable true real-time analysis. This can be achieved using direct infusion mass spectrometry, e.g. proton transfer reaction time-of-flight mass spectrometry (PTR-TOFMS). The described study involved immersion of food in hot oil and measuring the changes of the amount of released thermal degradation products. It was possible to capture the sudden burst of SOPs at the time of food immersion, which is explained by the immediate emission of water vapour, which, as it is released from the oil surface, facilitates rapid release of volatile organic compounds. The role of crust formation on the emission of SOPs was also observed. The study also revealed a link between the emission of volatile compounds and the deterioration of oil quality, making it possible to estimate the degree of oil degradation with progression of frying, and the measurement itself is done without stopping the process and collecting an oil sample. Hence, using PTR-TOFMS, it is possible both to monitor the formation of SOPs and to identify the link between the degree of oil degradation and the emission of volatile compounds.

The emission of volatile thermal degradation products during the early stage of deep-frying: emission profile determination using PTR-TOFMS

ACS Spring Meeting 2021

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