Degradation of green tea catechins in tea drinks

Green tea cateachins (GTC). namely (-) epicatechin (EC), (-) epicatechin ga llate (ECG), (-) epigallocatechin (EGC), and (-) epigallocatechin gallate ( EGCG), have been studied extensively for their wide-ranging biological acti vities. The goal of the present study was to examine the stability of GTC a s a mixture under various processing conditions. The stability study demons trated that GTC was stable in water at room temperature. When it was brewed at 98 degreesC for 7 h, longjing GTC degraded by 20%. When longjing GTC an d pure EGCG were autoclaved at 120 degreesC for 20 min, the epimerization o f EGCG to (-) gallocatechin gallate (GCG) was observed. The relatively high amount of GCG found in some tea drinks was most likely the epimerization p roduct of EGCG during autoclaving. If other ingredients were absent, the GT C in aqueous solutions was pH-sensitive: the lower the pH, the more stable the GTC during storage. When it was added into commercially available soft drinks or sucrose solutions containing citric acid and ascorbic acid, longj ing GTC exhibited varying stability irrespective of low pH value. This sugg ested that other ingredients used in production of tea drinks might interac t with GTC and affect its stability. When canned and bottled tea drinks are produced, stored, and transported, the degradation of GTC must be taken in to consideration.