Effect of pH and tea concentration on extraction of catechins from Japanese green tea

Factors that affect the extraction of green tea catechins were studied. Extraction efficiencies of major catechins, EC, EGC, ECg and EGCg, were decreased with use of a higher pH extradant because of epimerization of these catechins to the minor catechins, C, GC, Cg and GCg. Extraction efficiencies of gallo catechins, EGC and EGCg, were more affected by tea concentration than those of non-gallo catechins, EC and ECg. In water extracts of green tea, the pH decreased with increasing tea concentrations. Extraction efficiencies of non ester catechins, EC and EGC, increased with an increase in tea concentration, but for gallate catechins, ECg and EGCg, the efficiencies dropped at higher tea concentrations.