Kinetics and equilibria of tea infusion: Part 9. The rates and temperature coefficients of caffeine extraction from green Chun Mee and black Assam Bukial teas

Abstract

The rates of infusion of caffeine from green Chun Mee tea and from black orthodox Assam Bukial tea, using leaf of size 1.70–2.00 mm, were measured over a range of temperatures. The activation energies were found to be 62 and 40 kJ mol −1, respectively. The diffusion coefficients of caffeine within the tea leaves, calculated from the first-order rate constants at 80°C, were respectively 96 and 132 times smaller than the diffusion coefficient of caffeine in water at 80°C. These results show that diffusion of caffeine through the leaf is a greatly hindered process.