title: Altering the phenolics profile of a green tea leaves extract using exogenous oxidases.
abstract: Transformation from green tea leaves into black tea involves oxidation of catechins into theaflavins and other complex phenolics by endogenous enzymes in tea leaves. By employing tyrosinase and laccase, both from Agaricus bisporus, on green tea catechins, the oxidation process was directed towards a higher theaflavins content, which is considered an important quality parameter in tea. The main tea catechins were incubated with tyrosinase and laccase, and product formation was monitored by RP-UHPLC-PDA-ESI-MS. The kind of catechin, their substitution with a galloyl group, and the type of oxidase used were important factors determining theaflavin concentrations. In particular, incubation of epicatechin with epigallocatechin with tyrosinase gave a high, stable theaflavin content. In a green tea extract, tyrosinase increased the proportion of theaflavins by twofold compared to black tea. Laccase mainly formed insoluble complexes. Our results indicate that the phenolic profile of tea can be modulated by using commercially available exogenous oxidases.
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Annewieke J W
authors.initials: AJ
authors.lastname: Verloop
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Robbin
authors.initials: R
authors.lastname: Bisschop
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Electronic address: jean-paul.vincken@wur.nl.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Vincken
mesh_terms: D000364:Agaricus / Q000201:enzymology; D028241:Camellia sinensis / Q000737:chemistry*; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism; D042845:Laccase / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D018515:Plant Leaves / Q000737:chemistry*; D013662:Tea / Q000737:chemistry
chemical_list: D013662:Tea; D002392:Catechin; D042845:Laccase; D014442:Monophenol Monooxygenase
keywords: Black tea; Catechins; Green tea; Laccase; Theaflavin; Tyrosinase; UHPLC–MS