Research On The Mechanism Of Conversion Of Lignans Coupled With Decolorization In Sesame Oil

The total consumption of sesame in China is the first in the world,and more than 65%of it is used for oil production.The cake（residue）produced during the processing of sesame oil is still contains oil,protein and other substances,which are extracted by solvent to produce sesame crude oil,and sesame crude oil must undergo a refining process to produce refined sesame oil that meets the requirements of the national standards,but the economic value of refined sesame oil is low.Sesame lignans are characteristic active substance rich in sesame oil,which are transformed in the decolorization process,such as sesamin partially converted to asarinin.The conversion product asarinin is superior to sesamin in cell repair,anti-inflammatory and antitumor activities.In order to realize the high value utilization of refined sesame oil,this study investigated the catalytic reaction kinetics of the conversion of seamin into asarinin by preparing and screening a solid acid catalyst that can catalyze the conversion.On this basis,the effect of solid acid catalyst coupled decolorization process on the quality of sesame oil was explored.The application potential of the decolorized sesame oil as a skin care base oil was further evaluated,this study provides the technical support and theoretical basis to broaden the application prospect of sesame oil.The main research results are as follows:（1）Design and preparation of solid acid catalysts to promote the conversion of sesamin to asarinin:different types of solid acid catalysts were designed and prepared using high performance liquid chromatography（HPLC）to detect asarinin content.The results displayed that organic acid A loaded on Hβzeolite（CTAH）was the best catalyst,and the detail reaction conditions optimized by response surface experimental design were as follows:reaction temperature of 85℃,reaction time of 3.0 h,and catalyst addition of 1.6%,the amount of asarinin production reached 55.72 mg/100g.Compared with Hβzeolite,the specific surface area and pore size of CTAH were significantly increased after modification,and the number of strong acidic sites was increased by 67.21%,and its acid type was classified as L-acid combined with B-acid.（2）Effects of CTAH on the quality of sesame oil:the effects of solid acid catalysts including Hβzeolite,CTAH,phosphotungstic acid（PA）,and PTAH（PA loaded on Hβzeolite）on the lignans content,storage stability and in vitro antioxidant activity of sesame oil were investigated.The results showed that CK（heat-treated sesame oil only）and CA（organic acid A）treatments had no effect on the types of lignans in sesame oil;the production of asarinin was detected in sesame oil samples treated with solid acid catalyst（Hβzeolite,CTAH,PTAH and PA）;and there were no significant effects on fatty acid composition and content.Compared with CK（5.35 h）,the OSI values of Hβzeolite and CTAH treated sesame oil samples were significantly increased by 22.43%and 72.90%,respectively;the results of accelerated oxidation test in the oven showed that the total oxidation value of CTAH treated sesame oil sample was always kept at the lowest level;compared with CK,the IC₅₀ values of DPPH and ABTS free radical scavenging ability of CTAH treated with sesame oil sample were significantly reduced by 86.78%and 66.51%,respectively.The antioxidant capacity of sesame oil samples treated with solid acid catalyst was significantly improved.（3）Kinetic study of CTAH catalyzed the conversion of sesamin to asarinin:using CTAH（organic acid A loaded on Hβzeolite）as the catalyst,the changes of sesamin conversion in sesame oil system were reflected by reaction temperature,substrate concentration,catalyst addition and stirring rate.The results showed that the conversion of sesamin increased significantly with the increase of reaction temperature and catalyst addition.The kinetic model of the conversion of sesamin and asarinin was established by Athena Visual Studio software,the predicted data of the model were in good agreement with the experimental values(the correlation coefficients were R_Sesamin²=0.93 and R_Asarinin²=0.97,respectively).The enthalpy value of the reaction was 34.578 k J/mol according to the Van’t Hoff equation,indicating that the conversion of sesamin into asarinin in the sesame oil system was an endothermic reaction.The results of the reusability of CTAH showed that the catalyst was easily regenerated after calcination,and there was no obvious loss of catalytic activity during reuse.（4）Effect of solid acid catalyst coupled decolorization process on the quality of sesame oil:the effects of CTAH（organic acid A loaded on Hβzeolite）and other decolorizers on nutrient composition,flavor compounds and harmful substances of sesame oil during decolorization were evaluated.The results showed that the decolorization effect of CTAH was second only to the activated clay,there was no significant difference in oil yield between the sesame oil samples treated with CTAH and other decolorizers.The production of asarinin was detected only in the sesame oil samples treated with CTAH and Zn Cl₂ modified white clay.Compared with the sesame oil sample treated with active white clay,the retention rate of tocopherol in the CTAH treated sesame oil sample was significantly increased by 23.11%;the retention rate of phytosterols increased by 4.85%.The removal rate of the harmful substances Norharman and Harman from the sesame oil sample treated with CTAH was 96.79%,which was second only to the active clay;and the highest removal rate of total volatile compounds was 69.47%.The effect of different decolorizers on sesame oil samples were closely related to the specific surface area,pore size and surface acidic sites of these decolorizers.（5）Evaluation of the application of decolorized sesame oil rich in asarinin as a base oil for skin care:the differences in physicochemical quality and anti-aging activity between decolorized sesame oil treated with CTAH（organic acid A loaded on Hβzeolite）and commercial skin care base oils including olive oil,avocado oil,camellia seed oil and grape seed oil were compared and analyzed.The results showed that the p H values of different types of plant oil ranged from 4.49 to 5.96,which was closed to the p H state of human skin.The decolorized sesame oil had better oxidation stability than avocado oil and olive oil,and its total phenolic concentration was 58.26%higher than that of olive oil.The total tocopherol content of decolorized sesame oil（47.76 mg/kg）was significantly higher than that of camellia seed oil（5.26 mg/kg）.The unsaturated fatty acids content of varieties vegetable oils did not reach a significant difference level.The ability of decolorized sesame oil in scavenging DPPH and ABTS free radicals was outstanding（DPPH IC50 was 4.28 mg/m L）,followed by avocado oil（6.99 mg/m L）.The results of different types of vegetable oils on H₂O₂-induced oxidative damage of Ha Ca T cells showed that,within a certain cell-safe concentration range,both decolorized sesame oil and other vegetable oils had a delaying effect on cellular oxidative damage-induced senescence.