The Preparation And Separation Of Polypeptide Extracted From Selenium-enriched Tea

Selenium content of several kinds of Se-enriched tea was analyzed to choose appropriate tea as raw material.After that,the selenium-enriched protein was extracted,the tea peptide was obtained through enzymolysis and was isolated and analyzed.The results are as follow:Selenium content of chosen tea was 0.85 mg/kg,protein content was 32.76%,moisture content was 5.49%,ash content was 5.89%,fat content was 0%,total fiber content was 7.24%,carbohydrate content was 48.62%.For the alkali method,the optimum meal alkali concentration,extraction time,meal(solid)solvent(water)ratio,temperature were 0.1mol/L,2h,55?,50:1(w/v),respectively.The optimal pH of acid precipitation was 3.The optimal pretreatment method was that stirring extraction with acetone at 1:3 in room temperature for 30 min,the supernatant was then discarded,sediment was heated by 100? water for 30 min,after centrifugation,precipitates were collected for extracting.The optimal meal(solid)solvent(water)ratio was 60:1,alkali concentration was 0.1mol/L,stirring extraction with alkali in 80? for 1.5 h.Under that condition,extraction rate of protein was 54.29%,purity was 47.97%,Selenium content of crude protein was 1.47mg/kg,and content of selenium increased 1.7 times.The degree of hydrolysis and total antioxidant activity were investigated to choose optimal enzyme from neutral protease,papain and alkaline protease,The results indicated that enzymatic of alkaline protease has higher degree of hydrolysis and total antioxidant compared with neutral protease and papain.The degree of hydrolysis and total antioxidant activity were investigated to determine the function of enzyme dosage,concentration of substrate,temperature,pH and hydrolysis time,the optimal conditions were found as follows:enzyme dosage,0.05%;substrate concentration,15%;pH,7;hydrolysis temperature,55 ?;hydrolysis time,4 h.Enzymatic products were decolorized by HP20 resin then separated through superdex75 chromatography.Three kinds of peptide were obtained,the absolute molecular weight all lower than 6511 Da.