Extraction of tea polyphenols by ultrasonic-vacuum technology

【Objective】 This study analyzed the factors that affect the extraction of tea polyphenols by ultrasonic-vacuum technology and the extraction process was optimized.【Method】 Ultrasonic and vacuum technology was used to extract polyphenols from raw tea.The ethanol volume fraction,ultrasonic power,ratio of solution to solid,extracting time,extracting temperature and vacuum degree were researched.Based on single factor experiments,the best conditions were obtained using response surface methodology.【Result】 The results of single factor experiments showed that the highest extraction ratio was obtained when ethanol volume fraction,extracting time and temperature were 70%,15 min,and 70 ℃,respectively.The effects of ultrasonic power,ratio of solution to solid,and vacuum to the extraction process were lesser.The optimal ultrasonic power,ratio of solution to solid,and vacuum were 420 W,1∶15,and 0.7 MPa,respectively.Best extraction time,ethanol volume fraction,and temperature were 13 min,65%,and 65 ℃ by response surface methodology and the yield of tea polyphenols was 22.44%.Compared to reflux method,vacuum-reflux method,and ultrasonic method,vacuum-ultrasonic method reduced the extraction time by half.【Conclusion】 The technology can effectively shorten the extraction time and improve the extraction efficiency.