Ultrasonic Assisted Extraction and Purification of Tea Polyphenols from Tea Waste

In order to obtained highest extraction efficiency of polyphenolic compounds from tea waste, a rapid extraction method based on ultrasound-assisted extraction coupled with purification by ionic precipitation technique was investigated. According to the results of single-factor experiments, ultrasonic-assisted extraction was optimized by using response surface methodology (RSM) to obtain the best technique parameters of solvent concentration, sample/solvent ratio, temperature and extraction time. The crude polyphenols purification was carried out with ionic precipitation by using Zn2+ instead of Al3+. The results showed that the optimal combination of these factors on the ultrasound assisted extraction is a solvent composition 60% of ethanol, a sample/solvent ratio equal to 1:20(g:mL), a temperature of 61℃, and an extraction time of 30 min. The optimized purification agents for tea polyphenols were Al2(SO4)3/ZnSO4 ratio equal to 1:4. Under these conditions, the experimental yield and purity of tea polyphenols were 10.9% and 94.3%, respectively.