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

Stability of tea catechins during heat processing was exarnined. 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 lewer 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 belorv 95eC. A turning point temperature on an Arrhenius plot was obseryed at 82eC. A great difference of apparent activation energies was ol)served lower and higher than 82eC. The reaetion rate constant of catechins in slightly acidMed tea i"fusion 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.