Kinetics and equilibria of tea infusion: Theaflavin and caffeine concentrations and partition constants in several whole teas and sieved fractions

Concentrations of theaflavin and caffeine were determined in whole Kapchorua Pekoe Fannings and in six of its sieved fractions, as well as in Kapchorua Pekoe Dust, Betjan Flowery Broken Orange Pekoe and Rupai Flowery Orange Fannings and in one sieved fraction of each. The partition constants of theaflavin and caffeine between these leaves and water at 80°C were also determined. Neither property varied significantly with leaf size but did depend on leaf origin and manufacture. The concentration and partition constants for caffeine were greater than for theaflavin. As a corollary, the ratio of caffeine to theaflavin is larger in tea initially drawn from the teapot than in the beverage prepared after topping up with fresh hot water.