Degradation of Green Tea Catechins in Tea Drinks

Abstract

Green tea cateachins (GTC). namely (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC), and (-) epigallocatechin gallate (EGCG), have been studied extensively for their wide-ranging biological activities. The goal of the present study was to examine the stability of GTC as a mixture under various processing conditions. The stability study demonstrated that GTC was stable in water at room temperature. When it was brewed at 98 degrees C for 7 h, longjing GTC degraded by 20%. When longjing GTC and pure EGCG were autoclaved at 120 degrees C for 20 min, the epimerization of EGCG to (-) gallocatechin gallate (GCG) was observed. The relatively high amount of GCG found in some tea drinks was most likely the epimerization product of EGCG during autoclaving. If other ingredients were absent, the GTC 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, longjing GTC exhibited varying stability irrespective of low pH value. This suggested that other ingredients used in production of tea drinks might interact with GTC and affect its stability. When canned and bottled tea drinks are produced, stored, and transported, the degradation of GTC must be taken into consideration.

Determination of phenolic compounds and antioxidant activity of green, black and white teas of Camellia sinensis (L.) Kuntze, Theaceae

“…Rusak et al (2008) using HPLC showed that the catechins are predominant phenolic compounds in samples of Camellia sinensis and green tea is so rich in phenols as white tea, but the efficiency of the extraction depends on the infusion time and the solvent used. Astill et al (2001) and Chen et al (2001) also reported the influence of these factors and temperature on the extraction of phenolics and antioxidant activity.…”

Chá verde brasileiro (Camellia sinensis var assamica): efeitos do tempo de infusão, acondicionamento da erva e forma de preparo sobre a eficiência de extração dos bioativos e sobre a estabilidade da bebida

“…Estudos prévios sobre o preparo do chá verde têm demonstrado que o modo de preparo, tempo de infusão, forma de acondicionamento da erva, temperatura e a proporção peso seco da erva/quantidade de água utilizada têm grande influência na quantidade de compostos fenólicos e nas atividades antioxidantes extraídas (ASTILL et al, 2001;CHEN et al, 2001;ZHU et al, 1997). No presente estudo, foi avaliado também o efeito do volume de extração, mantendo-se sempre a mesma proporção de erva:água.…”

O chá verde e suas ações como quimioprotetor

“…Chen et al (2001) demonstraram que as catequinas são estáveis em água à temperatura ambiente, porém, quando aquecidas a 98 °C por 7 horas, apresentam degradação de 20%. A EGCG pura autoclavada a 120 °C por 20 minutos apresenta epimerização para galato-galocatequina (GCG), fato este que explica a alta quantidade da GCG encontrada em alguns chás e a presença dos quatro epímeros: catequina (C), galocatequina (GC), galato-3-catequina (CG) galato-3-galocatequina (GCG) nos chás engarrafados.Têm sido investigadas a atividade antioxidante e a biodisponibilidade destes epímeros, comparando-os com seus precursores.…”