Characterization of Tannase Activity on Tea Extracts

Abstract

Assay of tannase activity was performed directly, using extracts of black tea leaf, by a pH stat method at the pH optimum of the enzyme (6.0). Reaction rates were calculated from the initial rates of the volume of titrant vs. time plots, and activity was expressed as pmoles/min. The enzyme was unstable to pH levels above 6.0 and temperatures above 40°C. Optimum temperature was 35°C. Using saturating amounts of enzyme, the pH stat was also used to determine total hydrolyzable gallate for kinetic studies and to determine the effect of gallated polyphenols on loss of solids in instant tea processing.

Enzymatic modification by tannase increases the antioxidant activity of green tea

“…Hydrolysis reaction of green tea by tannase Thomas and Murtagh (1985) determined that optimum hydrolysis conditions for tannase from A. ficuum were pH 6.0 and 35°C. The hydrolysis reaction generally reaches equilibrium in about 20 min, although the enzyme concentrations vary.…”

“…doi:10.1016/j.foodres.2007.10.012 acid esters, liberating glucose and gallic acid (GA) (Lekha & Lonsane, 1997). Tannase also cleaves the ester linkages between galloyl groups and the various compounds such as EGCG or ECG present in green tea leaves (Lekha & Lonsane, 1997;Thomas & Murtagh, 1985). This release of GA is considered to be beneficial because of its significant antioxidant potency (Lekha & Lonsane, 1997;Niho et al, 2001).…”

Effect of tannase treatment on protein–tannin aggregation and sensory attributes of green tea infusion

“…Moreover, compared to the control, concentrations of both EGCG and ECG for tannase-treated green tea decreased with enzyme concentration until they were negligible, and this was accompanied by simultaneous increases in EGC and EC. This is because the ester bonds between gallic acid and EGC/EC in EGCG and ECG are cleaved by action of tannase, and produce gallic acid, EGC and EC (Lekha & Lonsane, 1997;Thomas & Murtagh, 1985). Approximately, 49% of the EGCG or ECG was hydrolyzed to EGC or EC after 20 min, respectively, if tannase (1.0 g/l) was used, with complete hydrolysis achieved at a concentration of 3.0 g/l.…”

“…Tannase was then added to the green tea infusion and reacted at 35 C for 20 min. Samples were withdrawn at intervals until the hydrolysis was completed (Thomas & Murtagh, 1985).…”

Microbial carboxylic ester hydrolases (EC 3.1.1) in food biotechnology

“…1986) 1983) and of potential use in the production of instant tea (Thomas & Murtagh 1985). Gallic acid esters have been synthesized enzymatically (Weetal 1985).…”