Kinetics of the extraction of black leaf tea

After analyzing the mass transfer properties of solute in high resistance and low resistance region, a two-component extraction kinetic model was developed. A three-parameter evaluation method of extraction kinetic process was established, which was used to evaluate the change of the ratio of fast solute, to predict equilibrium concentration and half-life time precisely. The results showed that drying method impacted the bulk density of Freedom black tea, which was related to tissue structural shrinkage and solute extraction characteristics. Fluidized bed dried and thin layer dried Freedom black tea had the best extraction characteristics followed by vacuum dried Freedom tea. The extraction characteristics of tray-dried Freedom tea were bad. Microwave dried Freedom tea displayed the worst extraction characteristics. The drying temperature of fluidized bed did not impact extraction characteristics. The small size fractions of Freedom black tea gave high ratio of fast soluble solids, short half-life time and high equilibrium concentration.