Effect Of Endogenous Antioxidant Components On Chloropropanol Ester Formation In In Camellia Oil During Thermal Processing And Its Mechanism

Chloropropanol esters are widely found in vegetable oils due to high-temperature refining.The potential detriment of chloropropanol ester is that it can be converted into free chloropropanol during gastrointestinal digestion.Chloropropanol has general toxicity,reproductive toxicity,carcinogenicity and genotoxicity.In recent years,a large number of studies have been devoted to mitigating the amount of chloropropanol esters in vegetable oils or other foods,some of which have been mitigated by adding antioxidants.However,to the best of our knowledge,vegetable oils contain some antioxidant components,such as tocopherol,phytosterol and squalene.Therefore,this study was carried out to investigate the effects of these endogenous antioxidants on the formation of 3-chloro-1,2-propanediol(3-MCPD)ester and 2-chloro-1,3-propanediol(2-MCPD)ester in camellia oil during thermal processing.The main results of this study are as follows:(1)This study developed a high performance liquid chromatography-tandem mass spectrometry(HPLC-MS)method for the simultaneous analysis of tocopherols(?-,?-,?-and?-tocopherol),phytosterols(?-sitosterol,stigmasterol,brassicasterol and campesterol),and squalene in vegetable oils,this method has been validated and applied.The results show that the method has good stability and precision with the peak area RSD ranged 1.7-5.7%and 0.66-3.66%,respectively;recoveries of nine analytes are in the range of 71.29-114.36%,with RSD values ranging from 0.9%to11.6%;The limit of detection(LOD)values are in the range of 0.0025-0.05mg/mL,and the limit of quantification(LOQ)values ranging from 0.01 to 0.2mg/mL.The current approach achieves the successful separation of?-and?-tocopherol,which solve the problem of coelution and inaccurate quantification for?-and?-tocopherol in previous study.A total of 40 vegetable oils in 9 categories were analyzed by this method,the results show that each vegetable oil other than camellia oil is rich in?-sitosterol(286.8-1131.7?g/g).Olive oil has abundant squalene(785.2-1491.3?g/g),corn oil,sesame oil and linseed oil are good source of?-tocopherol(186.4-310.0?g/g,184.2-237.0?g/g,117.3-197.5?g/g),sunflower oil is rich in?-tocopherol(202.9-303.8?g/g),rapeseed oil has ample brassicasterol(124.8-180.3?g/g)and campesterol(258.2-338.3?g/g).(2)The formation of 3-MCPD and 2-MCPD esters in camellia oil in FeCl₃and NaCl systems was compared,the results show that the higher and more stable3-MCPD and 2-MCPD esters are found in FeCl₃system,which indicates that Fe³⁺can promote the formation of 3-MCPD and 2-MCPD esters.Therefore,FeCl₃and camellia oil were seleted to establish hot processing simulation system,and then adding?-tocopherol,stigmasterol and squalene to investigate the changes of 3-MCPD and2-MCPD esters.The results suggest that?-tocopherol has both inhibitory and promoting effect on the formation of chloropropanol esters,and has good inhibitory effect when the addition amount is 5?g/g;the effect of stigmasterol shows promoting at low concentration and inhibiting at high concentration;different amount of squalene promote the formation of chloropropanol esters,and the effect are enhanced with the increase of squalene content.(3)1-glycerol palmitate and 1,2-glycerol palmitate were established reaction models with FeCl₃,respectively,and were scanned by fourier transform infrared(FT-IR)spectrum.According to the results,it can be inferred that the possible mechanism of 1-glycerol palmitate forming chloropropanol ester is that first form acyloxonium ion intermediate and a nucleophile substitution reaction occurs under the attack of chloridion;whereas 1,2-glycerol palmitate might be directly attacked by chloridion or first form glycidyl intermediate then attacked by chloridion to form chloropropanol ester.(4)?-Tocopherol,stigmasterol and squalene were added to the hot processed camellia oil,and then the free radicals were determined by electron paramagnetic resonance(EPR),the results suggest that four free radicals including Lipid Alkoxyl,CCl₃·?N₃·and SO₃·formed during camellia oil heating process,these free radicals may further mediate the formation of chloropropanol esters;After adding antioxidants,the amount of free radical formation in camellia oil was affected,and the species of free radical did not change.The effect of?-tocopherol on the amount of free radical was inhibiting at low concentration and promoting at high concentration;the effect of stigmasterol is promoting,but the effect is slight;squalene promotes the formation of free radical,and the effect are enhanced with the increase of squalene content.