Study On Modification Of Stigmasterol By Polyethylene Glycol And Application

Phytosterol is a class of natural active substances,which has the similar chemical structure with cholesterol.Thus it can reduce the level of cholesterol in the body by competing for the active site with cholesterol.It has been found that in addition to reducing cholesterol content,phytosterol also has a series of excellent properties such as anti-inflammatory,anti-cancer,antioxidant and so on,which involved in the pharmaceutical,food and cosmetic industries.But its poor solubility in water limits its application in food industry.This paper aims to improve the water solubility of phytosterol.Stigmasterol,a representativeof phytosterol,was selected as the experimental object.Polyethylene glycol with the property of high water solubility was employed as the modifier to modify the water solubility of stigmasterol.After that,the modified stigmasterol was applied to the beverage which provided a theoretical basis for broadening the application of phytosterol in the food field.The main research aspects of this paper are as follows:Firstly,polyethylene glycol was reacted with excess butyl two anhydride to obtain polyethylene glycol diacid.The molar ratio of polyethylene glycol to succinic anhydride was 1:5,and pyridine was used as catalyst.They were reacted in chloroform for 12 hours with the temperature of 70?.After solvent extraction,recrystallization,thin layer chromatography(TLC)and silica gel column chromatography,the products were characterized by Fourier transform infrared(FTIR)spectrum,and the existence of product in first step was proved.The product obtained in the first step were reacted with stigmasterol,and dichloromethane was used as solvent,DMAP and DCC as catalyst and water absorbent.TLC was used to monitor the reaction process.At the end of the reaction,the product was separated and purified by the method used in the first step.After characterized by FTIR,the existence of product obtained in the second step was proved.Secondly,the absorbance of stigmasterol at different concentrations was determined by ultraviolet visible spectrophotometer.The standard curve of stigmasterol was drawn and the linear regression equation was calculated by using concentration as abscissa and absorbance as ordinate.The consumption of stigmasterol was as the index,and the esterification rate was calculated.The effects of reaction temperature,time and molar ratio of alcohol to acid on the reaction were investigated by single factor experiments.On the basis of single factor experiments,the optimum reaction conditions were obtained through the optimization design of response surface with three factors and three levels.When the temperature was 65 ?,time was 18 h,and the molar ratio of alcohol to acid was 1.4:1,the reaction efficiency was highest,and the esterification rate reached 88%.The solubility of stigmasterol in water was 0.024 mg/ml,and the modified stigmasterol was 6.842 mg/ml.It was about 285 times than ever before.It was proved that the experimental method of using polyethylene glycol to improve the solubility of phytosterol was effective.In addition,the modified stigmasterol was applied to the beverage processing,and a kind of plant protein beverage was developed with soybean as the main raw material.The flavor,stability and processing technology of the beverage were studied respectively.The main ingredients of beverage flavor including sucrose,xylitol,citric acid and essence were carried out by single factor experiments and orthogonal experiments.The optimum addition amount was 6%sucrose,1.5%xylitol,0.15%citric acid and 0.06%essence.Under this condition,the beverage flavor value can reach 95 points.Then,the main stabilizers affecting the stability of beverage were studied.The stability was taken as the index,and the single factor tests and response surface optimization tests were carried out.The optimum addition amounts of four stabilizers including monoglyceride,sucrose ester,sodium carboxymethyl cellulose and xanthan gum were respectively:monoglyceride 0.1%,sucrose ester 0.1%,CMC-Na 0.1%,xanthan gum 0.08%.The stability of the beverage was 95%by the verification testing.In addition,the processing conditions were explored,and the optimum technological conditions were as follows:homogenization temperature 65,homogenization pressure 25 MPa,homogenization times 2,sterilization temperature 90°C,time 15min.Under these conditions,the stability of the beverage could be reached 98%.Finally,the quality indexes of the beverage,including sensory indexes,physical and chemical indexes,and microbial indexes,were determined.After 10 people's sensory evaluation,the average score was 96 points.In the physical and chemical indicators the content of protein was 5%,which met the requirements of the protein milk beverage.The microbiological indicators were also in line with the requirements of food hygiene.The samples were stored at 4?,25? and 37? respectively,and the sensory indexes were measured every 5 days.It was found that the beverage remained unchanged for nearly one month at 4?.Therefore,the research and development of this beverage is of practical significance.