A Method Of Extracting Tea Polyphenols By RF – Ultrasound Coupled Vacuum Reflux

Tea industry is the key characteristic agriculture industry in Shaanxi province.The tea area in southern Shaanxi is the key development area in the middle and upper reaches of the Yangtze river.At present,the green tea processing is the main industry in Shaanxi tea industry.The utilization ratio of tea raw materials is only 30%,and nearly 70% of crude and old leaves are wasted.The coarse and old leaves are the important raw materials for extraction of tea polyphenols.For the extension of tea industry chain,and the rational use of different seasons of tea.This study takes the Longjing No.43 and Pingli Camellia which in southern Shaanxi Province as the research objects.Study on variation of different growth period of total tea polyphenols and total catechins.To provide basic data support for extraction of tea polyphenols.The technology of radio frequency ultrasonic coupling vacuum reflux extraction of tea polyphenols was developed.The product of low caffeine tea polyphenols was obtained by macroporous resin purification.In order to provide technological support for the development of tea industrialization in southern Shaanxi Province,and improve the competitiveness of tea industry in southern Shaanxi Province.The main results are as follows:(1)Pinley camellia is more suitable for extracting tea polyphenols.In order to obtain tea polyphenols with high EGCG content,tea leaves at high altitude in 5~9 month can be selected as raw materials for processing.(2)In the radio frequency field,the distance between the plates,the volume of extracted solution and the amount of tea added have a significant influence on the heating rate of the tea polyphenols extraction system.(3)The effect of RF extraction rate factors: RF heating time,ethanol concentration and electrode spacing.The optimum extraction conditions were as follows: ethanol concentration was 60%,RF plate spacing was 114 mm,radio frequency treatment time was 327 s.According to the experience,the extraction rate of tea polyphenols was 16.55%.(4)The effect of RF-ultrasonic coupling vacuum reflux extraction rate of factors extraction method: extraction temperature,ethanol concentration,liquid-solid ratio and ultrasonic treatment time.The optimum extraction conditions were as follows: temperature65 ?,ethanol concentration 65%,liquid ratio 20:1,ultrasonic power 480 W,ultrasonic time5 min.According to the experience,the extraction rate of tea polyphenols was 18.37%.Compared with the traditional water bath extraction,ultrasonic extraction,ultrasonic coupling and vacuum reflux extraction,the extraction time was shortened by 55,25 and 15 minutes,respectively,and the extraction rate was increased by 14.74%,7.10% and 6.18% respectively.EGCG content is 2.96,2.10 and 1.31 times of traditional water bath extraction,ultrasonic extraction,ultrasonic coupling and vacuum reflux extraction respectively.(5)DM-130 macroporous resin separation of tea polyphenols conditions: resin diameter ratio of 1:15,the sample flow rate of 1 mL/min,elution flow rate of 2 mL/min.In the elution process,1 BV(5% HCL,10% ethanol)solution was used to remove the caffeine,and then 2.5BV 60% ethanol solution was used to elute the tea polyphenols.After washing with 5%HCL(10% ethanol),the content of caffeine was reduced from 6.56% to 3.48%.The purity of tea polyphenols was 92.53% after concentrated and dried.The content of EGCG was 42.03%,EGC content was 3.48%,ECG content was 15.48%,caffeine content was 3.58%.