In‐vitro studies on the effect of polyphenol oxidase and peroxidase on the formation of polyphenolic black tea constituents

Abstract

Flavanols (catechins and gallocatechins) isolated from green tea leaves (Camellia sinensis (L) 0 Kuntze) were treated in uitro with polyphenol oxidase, peroxidase and a combination of both. The flavanol levels and those of the products formed were monitored by reversed-phase high-performance liquid chromatography (HPLC) using spectrophotometric detection at 280 and 380 nm. Flavanols and theaflavins were quantified, whilst integrated peak areas are given for the remaining compounds. After fermentation in the presence of polyphenol oxidase higher levels of theaflavins and resolved thearubigins were obtained, whilst peroxidase produced higher amounts of chromatographically unresolved thearubigins of higher molecular weight, observed as a rise in the HPLC baseline. In the presence of peroxidase a significant decrease in the levels of all flavono1 glycosides was observed, whilst in the presence of polyphenol oxidase only myricetin glycoside levels decreased.

Bacteria and lignin degradation

“…Apparently, the enzyme extensively exists in bacteria, fungi, plants and animals (Alfred, 2006). In vitro studies have proven that polyphenol oxidase is involved in the degradation of natural phenols with more complex structures such as anthocyanins and flavanols (Finger, 1994). However, these compounds cannot be oxidized by the enzymes directly but by the quinones formed by polyphenol oxidase from catechol and catechin (Jiménez and García-Carmona, 1999).…”

Dynamic changes in flavonol glycosides during production of green, yellow, white, oolong and black teas from Camellia sinensis L. (cv. Fudingdabaicha)

“…However, the commercial tea products are normally collected from different company (Price et al ., ; Tan et al ., ), and it is difficult to control tea cultivar and leaf maturity which both affect the composition of flavonol glycosides. The degradation of flavonol glycosides was associated with the fermentation process of black tea (Price et al ., ), and this conclusion was testified by an in vitro fermentation study with polyphenol peroxidase (Finger, ). Dou et al .…”

Monitoring the fermentation process of black tea using QCM sensor based electronic nose

“…catechins are localized in the cell vacuoles of the undamaged tea leaf. The enzymes, polyphenol oxidase (PPO) and peroxidase (PO) are responsible for the oxidation of catechins [3,4]. During the rolling, stresses developed on the leaves, rupture the vacuolar membrane and thus allow the PPO and PO to mix with the catechins thereby initiating their oxidation process.…”