In this study (purchase required, USD$31.50) the researchers propose a combination of three galloylated flavonol glucosides, quercetin-(galloyl)-glucoside, myricetin-(galloyl)-glucoside, and kaempferol-(galloyl)-glucoside, as origin-specific geographical markers for Ceylon black teas
They identified these markers by untargeted analysis of reference samples of various tea types. They used quantitative UHPLC-DAD-Q-TOF-MS-based color-oriented metabolomics to systematically characterize the critical compounds associated with the bright-red infusion colour of Ceylon black tea and to further identify potential geographical markers for its authentication.
They report that five representative grades of Ceylon black tea differed in leaf appearance, but all produced bright-red infusions. Ceylon black teas undergo a relatively low degree of enzymatic oxidation, resulting in higher catechin contents and lower levels of theaflavins, thearubigins, and theabrownins. Untargeted colour-oriented metabolomics with orthogonal partial least squares regression analysis screened and identified 85 key low-molecular-weight compounds associated with infusion colour, some of which were further screened for geographical markers in Ceylon black tea, resulting in the three main candidate markers.
Their discriminatory performance was verified in an independent set of newly purchased black tea samples by targeted quantification using UHPLC-QQQ-MS/MS, followed by principal component analysis, which enabled clear separation of Ceylon black teas from black teas of other origins.
Photo by Jocelyn Morales on Unsplash
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