Study On Extraction And Purification Of Gamma Aminobutyric Acid And Protein Ftom Tea

Tea resources are rich in our country and the relative industry is develo-ping rapidly.Usually,only fresh tea is picked in the tea garden,while a large number of summer and fall tea has not been used or even abandoned,which caused a great waste.GABA,tea protein and other functional ingred-ients are contained in tea,which are benefit for human health.The full applying of these ingredients in tea can promote the effective use of tea resources.Therefore,our research tried to extract and purify GABA and tea protein from the fresh leaves of summer and fall tea as raw materials,the main research contents and conclusions were as follows:1.GABA in tea was extracted by the ultrasonic assisted method with the optimum process conditions as follows: temperature 50 ?,power 220 W,time 30 min.Under this condition,the GABA concentration was 0.095 mg/mL.Vacuum aerobic treatment 3 times was the best for the enrichment of GABA with the concentration of 1.02 mg/mL,increased 10.7 times;when the freezing time was 12 h,the concentration of GABA was the highest,1.13 mg/mL,increased 11.9 times.2.The effects of 8 kinds of resins on the purification process of GABA in tea were studied.The result showed that the separation effect of 732 type cation exchange resin was the best.The optimum conditions for the dynamic adsorption were as follows: the sample flow rate 3 mL/min,the sample concentration 0.2 mg/mL,eluant pH 9,eluant flow rate 2 mL/min.Under this condition,the retention of GABA was 78.26%,and the purity was 76.81%.3.Compared with direct alkali method,ultrasonic assisted method and freeze-thaw and ultrasonic synergistic method extracted tea protein,the results showed that the optimum conditions of direct alkali extraction of tea protein were as follows: liquid-solid ratio 24.05:1 mL/g,lye concentration 0.13 mol/L,extraction temperature 67.31 ?,extraction time 5 h;under this condition,the extraction rate of tea protein was 52.12%.The optimum extraction conditions were as follows: ultrasonic time 60 min,ultrasonic power 275 W,ultrasonic temperature 70 ?;under this condition,the extraction rate of tea protein was 70.88%.The optimum conditions for the extraction of tea protein by freezing and thawing with ultrasonic auxiliary were as follows: ultrasonic time 50 min,ultrasonic power 220 W,ultrasonic temperature 65 ?,freezing and thawing times 2 times;under this process,the extraction rate of tea protein reached 78.70%.4.The purification of tea protein and its structure and physicochemical properties were studied.The purity of tea protein was 88.57% by the precipitation of isoelectric point precipitation method,decolorization of hydrogen peroxide and ultrafiltration.Through the infrared spectroscopy analysis of tea protein,it indicated that the tea protein had the characteristic functional group of protein.Under the scanning electron microscope and atomic force microscope,it is observed that the tea protein was roughened and had lamellar structure and network structure,and the molecules were arranged closely in the form of spherical or rod.The physicochemical properties of tea protein were as follows: near the isoelectric point,the emulsifying and foaming were poor,the emulsifying stability and foaming stability were good;and tea protein has good oil absorption.