Role of Particle Size in Tea Infusion Process

Abstract

Two different types of CTC (Crush, Tear and Curl) teas were used for infusion kinetics study. Infusion kinetics for these and their ground and sieved fractions were studied over a 15-min period at 60°C and 80°C. Samples were analyzed using UV-Vis spectroscopy. Results of infusion have been interpreted in terms of gallic acid equivalence (GAE). Fractions with smaller particle size show faster infusion. First-order rate constants for largest and smallest fractions were 0.257-0.685 min-1, respectively, at 60°C. A quasi-steady-state model was developed, which determines initial dissolution rate, diffusion rate from actual infusion rate and hence rate controlling step. At 80°C, the infusion rate of the 0.33 mm granules was found to be 98% of the dissolution rate as compared to 68% in case of 1.99 mm granules. The diffusivity values were found to be 2.23×10-10 m2/s and 4.34×10-10 m2/s at 60°C and 80°C, respectively.