Optimization of the technology for polysaccharides extraction from middle and lower grade Oolong tea

Using mid-grade and low grade Oolong tea as raw material, the effects of temperature, time, the ratio of tea to water(w/v), the concentration of ethanol on the yield of tea polysaccharides were studied through orthogonal experiment, and the technology for deproteination from Oolong tea polysaccharides(OTPS) was investigated. Results show that the temperature of extraction has significant effect on the yield of tea polysaccharides, and the time of extraction, the ratio of tea to water, the concentration of ethanol have no significant effect. The optimum technological parameters are as follows: extraction for 80 min at 90℃ with 1∶25 ratio of tea to water, and 30% of ethanol concentration. The final OTPS yield was 10.15％, the purity of OTPS was 88.04%. After removing protein with sevag's method three times, the removing rate was 64.22%. In addition,infrared spectrum and ultraviolet spectrum analysis show that a majority of OTPS is pyranopolysaccharide, and there is typical absorption of protein in it.