| It contains natural antioxidant ingredients (polyphenols) in the tea, which ownssignificant health promoting effects and great application value. These have been widely usedin medicine and food industry.In this study, the following experiments were conducted successively on green tea: teapolyphenols testing for Extracting, concentrating experiment with RO (Reverse osmosis),purifying the crude Polyphenols and the Catechin monomers preparation technology. Thedetailed research contents were completed as follows:①Using ultrasonic assisted extractionmethod and Taking Temperature, time, Liquid ratio and ultrasonic power as the main factors,studying polyphenols extraction process conditions and Analysing the main factors affectingthe yield of tea polyphenols by response surface method.②Using of reverse osmosisequipment concentrated green tea extracts, Tests were carried out under different temperatures,operating pressure, to optimize the process conditions.③The tea polyphenol extracts werepurified by using solvent extraction method, studying on extraction of time, temperature andthe amount of solvent effects on its yield, And the optimum process conditions weredetermined.④Using the crude polyphenols and the catechin monomers were isolated andpurified by preparative liquid chromatography. The mobile phase in these methods weremethanol-water and acetonitrile-water; C18column (SMB100-1010μm, GLP-ID50×450mm,310g), sample was1.2g, detection wavelength was275nm, flow speed was30mL·min-1atroom temperature. The conditions were optimized. With eventually mass spectrometer toidentify the structure of each catechin. The main results were described as follows.(1)The selection of water was as extraction solvent, the experimental conditionoptimization of single factor experiment and response surface method.The optimal processconditions were as follows: extraction temperature was79.93℃,extraction time was24.17min,Ultrasonic power was411.36W, liquid ratio was21.84mL·g-1. Under this process conditions,the yield of tea polyphenols can reach to19.079%.(2)Reverse osmosis equipment polyphenols extract was concentrated processing.Through the test, get the optimum conditions: Operating temperature was45℃, Operatingpressure was14.0bar. Under this condition, the average water flux of membranes was 5.8L·m-2·s-1, the tea polyphenol extract was concentrated to the original volume of1/4.(3) The chloroform extracted caffeine, successively, ethyl acetate extracting polyphenols.Through testing, to determine the optimum conditions for the extraction of caffeine：Liquidratio was3, extraction time was20min at room temperature. The separated aqueous phasewas extracted by ethyl acetate. the optimal process condition was obtained: liquid ratio was2.5,extraction time was24min, temperature was10℃.Under this extraction condition, the teapolyphenols extraction rate can reach to77.37%. UV spectrophotometric detection ofpolyphenols content was93.0%.(4)The mobile was acetonitrile-water, gradient elution was used as(phase B):14%(10min),14%-16.5%(63min),16.5%(20min),16.5%-20%-27%,(15min-21min). Thecatechins obtained were analysed by HPLC, the catechin monomers as epigallocatechingallate (EGCG), epicatechingallate (ECG), epigallocatechin (EGC) were separated andpurified. Freeze-dried and Calculated by weighing, obtained179.4mg of EGC,428.5mg ofEGCG,87.3mg.Their purities are97.1%,99.0%,98.2%. The purity of by-product caffeinewas93.8%,7.03mg.When the mobile was methanol-water, gradient elution was used as(phase B):18%(10min),18%-19.5%(60min),19.5%(40min),19.5%-50%(30min).The catechins obtainedwere analyzed by HPLC, EGCG with by-product caffeine did not get completelyseparation.87.3%purity of EGC,91.6%purity of ECG were harvested.The structures of the catechins were subsequently confirmed by analysis of LC-MS/MS. |
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