THE KINETICS OF EXTRACTION OF INDIVIDUAL FLAVANOLS AND CAFFEINE FROM A JAPANESE GREEN TEA (SEN-CHA-UJI-TSUYU) AS A FUNCTION OF TEMPERATURE

Rates of infusion for the four major tea flavanols from a Japanese gre en tea have been measured for the first time. The results indicate tha t the ungallated epicatechin and epigallocatechin infuse faster than t he gallated flavanols epicatechin gallate and epigallocatechin gallate . The infusion rate is shown to be related to the inverse of the squar e root of the mass of the molecule. This gives support to the idea tha t the rate-determining step of the infusion process is a diffusive one . The temperature-dependence of the infusion of the four flavanols yie lds activation energies of 30 and 50 kJ/mol. In addition, rates of inf usion of caffeine from the green tea and its temperature-dependence we re investigated. These results indicate that the caffeine infusion rat e and the activation energy are significantly larger than for the four flavanols and also larger than for caffeine infusion from black teas. This latter aspect is discussed in terms of differences in manufactur ing techniques between black and green tea.