Study On The Control Of α,β-unsaturated Aldehydes Derived From Vegetable Oils By Polyphenol Antioxidants And Its Mechanism

α,β-unsaturated aldehydes are a class of carbon-carbon double bonds located betweenαandβcarbon atoms of active carbonyl compounds.They are mainly derived from oxidation of unsaturated fatty acids,and excessive intake can cause nerve damage,cardiovascular disease and even cancer.The oil consumption of China is high,and oils are prone to be oxidized during processing and storage to generateα,β-UAs.Meanwhile,due to the differences in the structures ofα,β-UAs,there is still a lack of methods for the systematic determination.Therefore,the establishment of a simple and efficient detection method is of great significance.This dissertation were aimed to take common oils as the research object,and tried to establish a detection method of mainα,β-UAs in oils simultaneously,and preliminarily discuss the relationship between the formation ofα,β-UAs and fatty acid composition;and then,ω-3,ω-6,ω-9vegetable oils were used as research objects to study the formation of differentα,β-UAs under heating and storage conditions and the effect of polyphenol antioxidants on the control ofα,β-UAs;finally,the model system and high performance liquid chromatography method were established with acrolein as representative ofα,β-UAs,and the acrolein scavenging activity of different polyphenol antioxidants was evaluated,and the adduct of antioxidant and acrolein was synthesized to elucidate the scavenging mechanism.The main research content and results are as follows:（1）Establishment of a method for simultaneous detection ofα,β-UAs in oil by supercritical CO₂chromatography tandem triple quadrupole mass spectrometry （SFC-MS）A method for the determination ofα,β-UAs in oils by SFC-MS was established,and the chromatographic and mass spectrometric conditions forα,β-UAs-DNPH were optimized.According to the methodological verification,the LOD and LOQ of the target aldehydes were much lower,the daily RSD was lower than 6.29%,and the recovery rates were higher than 83%,showing good accuracy and reproducibility.Moreover,the total sample analysis time was 16 min,greatly improving the analysis efficiency.The derivatization time was 30 min,the amount of DNPH added was 4 mg,and the extraction time was 4.More than 99%ofα,β-UAs in oils were extracted by using the established method.With this method,the content changes ofα,β-UAs in the heating process of 8 kinds of oils were measured,and it was found that the oils rich inω-3 fatty acids were more likely to produce malondialdehyde,pentenal,hexenal,2,4-heptadienal,acrolein and 4-hydroxy-2-hexenal,while heptenal,2,4-decanenal and 4-hydroxy-2-nonenal are mainly formed from the oxidation of oils rich inω-6 unsaturated fatty acids,highlighting thatα,β-UAs are easier to be produced in the oil with higher unsaturated degree.（2）Study on the control of the accumulation ofα,β-UAs in typical oils by polyphenolic antioxidantsLinseed oil,corn oil and high oleic sunflower oil were selected as the representative of omega-3-,omega-6-and omega-9-type vegetable oils,respectively,to investigate the control of polyphenol antioxidants with different structures on theα,β-UAs during heating and storage,and the results are as follows:the formation of malondialdehyde and 4-hydroxy-2-hexenal were the highest in linseed oil,while the content of 4-hydroxy-2-nonenal is the highest content in corn oil.The formation ofα,β-UAs during storage was significantly lower than that during heating process,which indicated that the formation ofα,β-UAs was temperature-dependent.Polyphenol antioxidants with different structures showed different control onα,β-UAs formation,with epigallocatechin gallate（EGCG）and tea polyphenol palmitate showing the highest inhibitory effect,and butylated hydroxytoluene（BHT）showing nearly no inhibitory effect.Compared with heating process,polyphenol antioxidants were more effective under storage conditions.In addition,it was also found that all five polyphenol antioxidants could inhibit the increase of peroxide value effectively during oil storage,which was inconsistent with the their control effect onα,β-UAs,indicating that the inhibition of oxidation was not the pathway of the limitation ofα,β-UAs accumulation.Finally,by comparing the changes in the retention rate of polyphenol antioxidants in oils and saturated triglycerides during heating and storage,it was found that the loss of polyphenol antioxidants in oils was not attributed to thermal degradation,but a scavenging reaction withα,β-UAs.（3）α,β-UAs scavenging activity and mechanism of polyphenolic antioxidants with different structures in model systemBased on the above results,acrolein was selected as the representative ofα,β-UAs to study the scavenging reactions and the mechanisms.The results are as follows:the scavenging activity of different polyphenol antioxidants are significantly different with the order of 50%DMSO>PBS>90%DMSO.Moreover,in the methanol system,acrolein reacted with methanol to form the adduct,resulting in false positive results.In the same model system,acrolein scavenging activity of different polyphenol antioxidants followed the order:tea polyphenol palmitate>propyl gallate>carnosic acid>TBHQ>BHT,showing the same order of control of polyphenol antioxidants onα,β-UAs in vegetable oils.In addition,comparing the scavenging ability of alkyl gallates with different carbon chain lengths,it was found that the scavenging effect decreased with the increase of the number of carbon atom of the introduced alkyl chain;however,the number of palmityl group introduced into EGCG did not influence acrolein scavenging activity of EGCG,highlighting that the effect of ester modification of polyphenol antioxidants on their carbonyl scavenging capacity was determined by their structures.Moreover the longer the carbon chain ofα,β-UAs,the lower scavenging ability of polyphenol antioxidants.Finally,the adducts formed from scavenging process was analyzed it found that the hydroxyl group in the structure of propyl gallate and the non-substituted carbon atom on its benzene ring can trap acrolein to generate propyl gallate-mono-and di-acrolein adducts.