Detection And Application Of The Method For Oxidized Triacylglycerol Polymers

The triacylglycerol oxidized polymer(TGP)in oils and fats is a gold indicator for evaluating the oxidative deterioration of oils and fats,but its current measurement method is time-consuming,material-intensive,and inaccurate.In order to establish a simple,rapid and accurate analytical method for the determination of oxidized triacylglycerol polymers(TGP)in oils and fats,non-polar components(Non-PC)and polar components(PC)such as oxidized triacylglycerol oligomers(TGO),oxidized triacylglycerol dimers(TGD),oxidized triacylglycerol monomers(ox-TGM),diacylglycerls(DG)and free fatty acids(FFA)were separated by high performance liquid chromatography and detected by evaporative light scattering detector with two sequential columns(forward silica column connected with gel column).The external normalization method was used to quantify TGP,and the limit of detection(LOD),the limit of quantitation(LOQ),accuracy,recovery and repeatability of the two sequential columns method were determined.Forther more,this method was used to evaluate the TGP(%)in olive oil under different oxidation modes.The main results are as follows:1.Among the 7 kinds of kitchen waste oil determined by the AOCS method,there are 3 kinds of waste oil whose polar components content is less than 27%.Therefore,he polar component is not accurate as an index for evaluating the quality of oil and fat,while the TGP(%)of two vegetable oils is less than 1%,which is obviously different from the waste oil in kitchens and kitchens,so TGP is expected to become an effective indicator for evaluating the quality of oils and fats.2.DG was used as external standard to quantitatively determine TGP in oils combined with area normalization method.The eluent used was a gradient of petroleum ether(A)and tetrahydrofuran(B).Elution was performed at a solvent flow rate of 0.7m L/min with a linear gradient as follows:0 min 5%B,20 min 15%B,30 min 30%B,35 min 5%B,keeping these conditions during 50 min.3.The two sequential columns method showed that the TGP provides nonlinear response curves,with correlation coefficients(R~2)was 0.9995,the LOD of TGD was156 mg/L,and the LOQ was 267 mg/L.The recoveries of the spiked DG of the method were between 95%and 99%with the relative standard deviation(RSD)less than 2%.Moreover,the method provided good repeatability for TGP in the detection of oil and fat with RSD less than 3%.This method can quantify the content of TGP in oils and fats within 1 h,which is easy to operate and accuracy quantitative,and saves experimental materials.4.Use a known single standard to quantify multiple homologs without standards at the same time,the quantitative calculation formula of the homologues was first derived according to the external standard method and the normalization method as Ci=((b Ar+a)Ai)/Ar(C:Substance concentration;A:peak area;i:any homologue;r:known external standard;b,a:constants of the standard curve,respectively),and naringin as the external standard,and simultaneously measure its The homologues of neohesperidin,hesperidin and rutin,compare the measured value with the calculated value of the above formula.The comparison results show that the relative deviation between the calculated amount of the three homologues and the actually measured homologue content is between 3.3%and 5.4%,and the relative standard deviation(RSD)is less than 1%.5.Under 180?and 12 h frying conditions,the content of TGP in olive oil increased from 0.35%to 2.54%,the formation rate increased continuously within 12 h,indicating that the oxidation polymerization speed of ox-TG increased at high temperature.When the temperature is lower than 150?,the higher the heating temperature is,the higher TGP(%)is;but when the temperature is higher than 150?,the amount of TGP generated in olive oil is around 1.24%,there is no significant difference of TGP(%)in olive oil.Indicating that the frying environment causes the induction period to disappear,and high temperature and hypoxia are not conducive to the formation of ox-TGM from TGM.Different antioxidants with the same concentration were added to olive oil and heat at 180?for 10 h,compared with the blank sample,TBHQ,BHA,BHT and PG increase the antioxidant capacity of olive oil by 34%,23%,24%and 20%,indicating that TBHQ has a better antioxidant effect on olive oil.The above theoretical and experimental results confirm that the method of quantification by external standardization method and the separation and determination of TPG in oil and fat by double column method are simple,accurate and fast.