Effect Of Different Heating Methods On The Generation Of Persistent Free Radicals In Unsaturated Fatty Acid

As an emerging environmental pollutant,the environmental persistent free radicals(EPFRs)have drawn much attention due to its toxic effect and health risks.It is well known that edible oil is an essential part of people’s daily life.However,the formation and health risks of EPFRs in edible oils are often ignored during daily cooking and frying.In this study,we investigated the formation and attenuation characteristics of EPFRs in three unsaturated fatty acids(UFAs,an important component of edible oil),including linolenic acid(LNA),linoleic acid(LA)and oleic acid(OA),under different heating methods and time by simulating daily cooking methods.We further characterized the variance of physicochemical properties of three UFAs before and after heating,to clarify the influencing mechanism of different heating methods and time on the generation of free radicals in three UFAs.This study would provide a theoretical basis for evaluating the health risks of EPFRs in edible oils and guiding the use patterns of daily cooking.The main achievements of this study are as follows:(1)The obtained results showed that significant EPFRs signals were detected when three UFAs were stove-heated to 180 °C.Additionally,the stable EPFRs signals were further increased when microwave was used to reheat the previously stove-heated samples.Meanwhile,GC-MS results demonstrated that the benzene ring structures generated after microwave-reheating were involved in the formation and stabilization of free radicals.(2)The variance of physicochemical properties of three UFAs before and after heating was investigated in this study.The results showed that the polarity of UFAs increased and chain length of UFAs decreased after stove-heating,which can provide the much sites for the generation of free radicals.(3)The free radicals produced by stove-heating and microwave reheating were oxygen-centered free radicals.FTIR results showed that signals of C=C and C=O bonds of UFAs were progressively weakened with the increasing heating time.Comparing with the variance of the free radicals intensities among three UFAs,it was found that the C=C 和 C=O were the sites for the formation of free radicals and the number of double bond was an important factor affecting the intensities of free radicals.