Study Of The Technology And Application On Extracting Teapolyphenols From Tea Leaf With Microwave Extraction

Using the microwave-assisted extraction of teapolyphenols from tealeaves as a model process, the acceleration of microwave energy duringextraction was discussed, the effects of solvents, the volume of solvents,microwave radiation time and the volume of wetting water were studiedin this paper. The results are as follows:When the extraction solvents used in the MAE are of greater polarity,the acceleration of microwave energy on the breakage of cells isexplained by the hot expansion, besides, there is possibly an effect ofelectrical breakdown.The choice of extraction solvent is found to be of great importance.For MAE, the solvent used as the extractant requires not only goodsolubility, but also proper ability to receive the microwave energy andtransform it into thermal energy. The optimized solvent is ethyl acetate.The effect of solvent volume on the extraction amount ofteapolyphenols is dependent on the type of solvents. For non-polarsolvents, the increasing volume of solvents had no remarkable effect onthe extraction result; for polar solvents, the amount of solvents should beas low as possible in order to obtain higher efficiency of microwaveenergy. The extraction rate of teapolyphenols obviously increased when tealeaves are wetted. The volume of wetting water should be as low aspossible in order to obtain better results, because the proper volume ofwetting water could be completely absorbed by tea leaves, then waterbecame the micro-medium of exchanging substance and energy betweentea leaves and ethyl acetate. When radiated by microwave energy,teapolyphenols and heat could be transferred into ethyl acetate. With thevolume of wetting water increasing, the extraction rate decreased byinches, because over much water could increase radiation time andcaused increasing of oxidation in process of extraction.The longer microwave radiation time is, the more teapolyphenols areextracted. The increase is great within less time, but the increase begin tolevel off beyond this range.According to an orthogonal experimental design, the optimumextraction conditions are obtained: for teapolyphenols, 27% microwavepower, 9 min irradiation, 40ml/g solvent volume and 4ml/g wetting watervolume.In the study, the roughhewn teapolyphenols aider extraction arepurified and separated, and the contents of some sorts of catechol couldbe exactly analyzed in HPLC with such advantages as short time foranalysis, easy operation, and so on. The optimal conditions for HPLC areas follows: the methanol: redistiled water:acetic acid (25:75:0.5, v/v/v)mobile phase and UV detection at 270 nm, using Spherigel C₁₈chromatographic column (120×4.6mm, i.d.5μm), temperature at 25℃andvelocity of flow at 1.0ml/min.On basis of the composition, structure and its microwave extracting theory,the optimal microwave extracting process of teapolyphenols from tea leaf isinvestigated and determined. Experimental results by HPLC and UV-Spectrashow: the process of purification and separation is reasonable after extraction.