Effect of Ultrasonic-assisted Extraction Coupled with Electrodialytic Desalination on the Physicochemical Property of Green Tea Infusions

In this article, the impact of different extraction methods (including ultrasonic-assisted hot water extraction and conventional hot water extraction) on the physicochemical property of green tea infusions was investigated. Moreover, the influence of the electroosmosis process on the turbidity and precipitation rate of green tea infusions before and after cooling was also evaluated. The results implied that the contents of soluble-solid, catechin and caffeine in green tea infusions extracted by ultrasonic-assisted hot water method were higher than those extracted by conventional hot water extraction alone. With increasing of the ultrasonic power, the levels of catechin and caffeine in green tea infusions firstly increased and subsequently decreased, and reached the maximum values (5903.14 and 1091.87 mg/kg, respectively) when the ultrasonic power elevated to 390 W. The results also indicated that the level of metal ions and electrical conductivity were significantly decreased after electrodialysis treatment. After electrodialysis treatment of green tea infusions extracted by hot water extraction alone and ultrasound-assisted hot water extraction at power levels of 130 W and 390 W, the removal rates of potassium were 67.46%, 80.20% and 89.59% respectively, the removal rates of manganese were 64.92%, 77.35% and 88.56% respectively. The turbidity of green tea infusions significantly deceased and the formation of tea cream after cooling was obviously inhibited after electroosmosis treatment.