Effects of pH and Temperature on Reaction Kinetics of Catechins in Green Tea Infusion

Abstract

Stability of tea catechins during heat processing was examined. Effects of pH and temperature on reaction kinetics of degradation of tea catechins were investigated. Reaction of -EC was accelerated at pH higher than 6.0, inhibited at those lower than 5.0. A dominant reaction of -EC in slightly acidic media was isomerization. The apparent first order reaction proceeded in slightly acidic media under sterilization conditions. A similar reaction proceeded for -EC, -EGC, -ECg, and -EGCg in green tea infusion at temperatures below 95°C. A turning point temperature on an Arrhenius plot was observed at 82°C. A great difference of apparent activation energies was observed lower and higher than 82°C. The reaction rate constant of catechins in slightly acidified tea infusion was less than half as much as the constant in the original infusion. The stability of catechins in green tea infusion was subject to the turning point temperature.