Effects Of Sesame Lignans On Inhibiton Of Glycidyl Esters In Vegetable Oil During Simulated Deodorization And Deep-frying

Glycidyl Esters(GEs)have been identified as a new class of associated chemical hazards produced by oil-thermal processing which were mainly formed during the deodorization step of oil-refining processes.Apart from deodorization,deep-frying at high temperature also seem to result in the potential formation of GEs in edible oils and oil-based food products.With the further study of GEs generation and inhibition recently,the addition of antioxidants can effectively inhibit the formation of GEs during the deodorization step of oil-refining processes and deep-frying.Sesame lignans,a class of naturally occurring oil-soluble antioxidants,are potential substitute to replace the synthetic antioxidants because of their safety and strong antioxidative properties.Sesamolin and sesamol are the major sesame lignans present in sesame oil which can contribute stronger antioxidant capacity duing to their transformation.In present research,firstly an efficiently accurate quantitative method for GEs detection through ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)was established.After that the effects on inhibiting GEs formation with the addition of sesamolin,sesamol,and cold-squeezed sesame oil during oil-refining processes and deep-frying were investigated.The main results are shown as follow:(1)Establishment of UPLC-MS/MS for the analysis of GEs in edible vegetable oilsAn improved method based on UPLC-MS/MS for the analysis of GEs in edible vegetable oils was established.With the increased loading quantity of sample for pretreatment,the analytical concentration of target substance was increased while satisfied the detection for samples with lower GEs content.The elution procedure was optimized which avoided the loss of mobile relative chromatographic column and reduced the use of organic solvents.The total time of elution procedure was 15.2 min which was at least 31%shoter than current methods making the method more efficient.After optimizing through daughter ions mode,the quantitative ion selected for C16:0-GE,C18:0-GE,C18:1-GE,C18:2-GE and C18:3-GE were71,71,95,95 and 95 respectivly.The multiple reaction monitoring mode(MRM)was adopted to quantitative detection which offer more specific on the detection of five GEs.The minimum detection limit of five GEs ranged from 0.0045 mg/kg to 0.023 mg/kg.The average recovery rate was 96.16%to 107.02%with the relative standard deviation of 1.98%to 5.74%.This method was practical with high sensitivity and good reproducibility which can meet the demands of the efficiently accurate detection and analysis of GEs in edible oils.(2)Effect of the addition of sesame lignans and cold-squeezed sesame oil on inhibiting GEs formation in model vegetable oil during deodorization step of oil-refining processesThe results showed that the addition of sesamolin and sesamol could effectively inhibit the formation of GEs in model vegetable oil(Model palm oil(MPO),Model corn oil(MCO)and Model rice bran oil(MRO)),and the inhibition rate of GEs increased with the increase of sesamolin and sesamol.However,the inhibitory rate of GEs in different model vegetable oils were different which were ranked as MCO(19.84%)>MRO(17.34%)>MPO(15.65%)with tha maximum addition(0.10%)of sesamolin and MPO(28.99%)>MRO(19.00%)>MCO(17.48%)with tha maximum addition(0.050%)of sesamol.According to the inhibiting effect of sesamolin and sesamol on GEs and the contents change between sesamolin and sesamol,we found out sesamol is the effective component to inhibit GEs formation.The results of fourier transform infrared spectrometry(FTIR)also showed that sesamol could probably inhibit the generation of cyclic acyloxonium intermediate(CAI)by capturing free radicals or directly acting on the generation of CAI leading to the inhibition of GEs.We also found out the effect of addition of cold-squeezed sesame oil(SO)on the contents of GEs in three model oils was mainly due to the significant reduction of DAG,the precursor of GEs formation in model oils,rather than the inhibition of sesamin and sesamol(P<0.05).With the increase of SO addition,the inhibition rate of GEs formation of the three model oils was increased as well as the content of unsaturated fatty acids in the model oils and the initial oil quality were improved.At the same time,during to the addition of SO,the oxidation stability of MCO and MRO was improved,but the oxidation stability of MPO was decreased(P<0.05).(3)Effect of the addition of sesamol on inhibiting GEs formation in palm oil(PO)during continuous deep-fryingThe results showed that Sesamol can effectively reduce the content of GEs in palm oil during the continuous deep-frying process for potato cube,but the change of GEs content in during deep-frying process was mainly manifested in the initial heating stage from 25~°C to180±2~°C and the first frying(5 min).After the first frying,the percentage of GEs decreased by14.45%compared with that in the fresh palm oil.With the increase of sesamol addition from0.025%to 0.10%,the percentage of GEs in oil samples decreased significantly by 16.92%,20.30%,22.35%and 26.25%respectively,which showed that the decrease of GEs content was improve with the increase of sesamol additive amount(P<0.05).There was no significant difference in the percentage of GEs in oil samples during the subsequent 8 hours continuous frying process(P>0.05).Besides,sesamol can play an antioxidant role and scavenge free radicals which could slow down the oxidation,polymerization and decomposition of frying oil as well as delay the oxidative deterioration and improve the stability of palm oil.