Study On The Extraction Of High Active Silybum Marianum Oil And Its Microencapsulation

Silybum marianum oil（SMO）is a new resource oil extracted from the seeds of the genus Silybum marianum from the family Asteraceae.It contains a lot of unsaturated fatty acids,a variety of active substances and rich in nutritional value.However,there are few studies on SMO at home and abroad.In addition,the oil is susceptible to rancidity and oxidation during the processing,storage,and transportation.The storage period of the oil is short,and the liquid form of the oil also limits its application.Microencapsulation can not only delay the oxidative rancidity of the oil,but also change its physical properties.Therefore,in this dissertation,the antioxidant activity of SMO extracted by ultrasound-assisted mixed solvents from Silybum marianum was studied.Then,the Silybum marianum oil microcapsule（SMOM）was prepared by spray drying.This not only improved the active of SMO,but also changed its morphology and expanded the application scope of SMO.This study will provide theoretical basis and technical support for further development and utilization of SMO.The main research contents and results were as follows:1.The optimal conditions for extracting highly active SMO with ultrasound-assisted mixed solvents were studied.The extraction rate of SMO and the 50%inhibitory concentration(IC₅₀)of DPPH·were taken as the indexes.The best mixed solvent of petroleum ether and ethanol was selected from six kinds of commonly used solvents,and the best ratio of them was 7:3.On the basis of single factor test,response surface method was used to optimize the optimum process conditions of SMO:ultrasonic power 240 W,ultrasonic time 20 min,liquid-material ratio 4:1.Under this condition,the extraction rate of SMO was 16.19%and the IC₅₀0 of DPPH·was 10.27mg/mL.2.The fatty acid composition,physicochemical properties,main active components and antioxidant activity in vitro were compared between SMO A extracted from mixed solvent and SMO B extracted from petroleum ether.On this basis,the antioxidant effect of SMO A on Caenorhabditis elegans（C.elegans）was further studied.The results showed that the fatty acid composition and content of SMO A and SMO B were basically the same.The contents of insoluble impurities and non-saponification in SMO A were slightly higher than that of SMO B.The contents of active ingredients such as flavonoids,total phenol,sterols and VE in SMO A were also higher than that of SMO B.The scavenging ability of SMO A to DPPH·,ABTS free radicals and hydroxyl radicals,as well as its reducing power and total antioxidant capacity were better than those of SMO B.These indicated that SMO A had stronger antioxidant activity in vitro.In addition,it was found that different concentrations of SMO A could not only prolong the life of nematodes,enhance their exercise ability,increase their number of offspring,but also significantly enhance the resistance of nematodes to heat stress and oxidative stress.3.The preparation conditions of highly active SMOM were studied.Firstly,the emulsification stability was taken as the index,the best composite wall materials for microcapsules selected from 7 wall materials were gum arabic and maltodextrin.When the ratio of gum arabic and maltodextrin was 1:1,the embedding rate of SMOM was the highest（76.03%）.On the basis of single factor test,the central composite design was used to optimize the optimum process conditions of SMOM:gum arabic:maltodextrin 1:1,solid content 20%,wall material:core material 5:1,emulsifier content 2%.Under this condition,the embedding rate of microcapsules was 80.51%.4.The physical and chemical properties and storage stability of highly active SMOM were studied.The results showed that SMOM had low water content,low viscosity,and good solubility and fluidity.The particle size and morphology of the microcapsules were analyzed by laser particle size analyzer and scanning electron microscope.The results showed that the microcapsules were nearly spherical,the surface was relatively smooth,the particle size was 2-10μm,and the distribution was relatively uniform.The thermal stability of the microcapsules was analyzed by a comprehensive thermal analyzer.It was found that the microcapsules had good thermal stability and could keep the structure integrity during the conventional thermal processing.The fatty acid composition,peroxide value and oil retention rate of microcapsules during storage were studied.The results showed that the content of fatty acids in microcapsules changed a little before and after storage,while the change rate of peroxide value of oil in microcapsules was lower than that of SMO,which indicated that microcapsules had a good embedding and protection effect on SMO,and effectively delayed the oxidative rancidity of SMO.After seven days storage,the oil retention rates of SMOM under the conditions of 25℃and 60℃were 97.81%and96.32%,respectively,which also indicated that the microcapsules had good storage stability.