This review (open access) covers the main approaches for verifying tea traceability, including sensory analysis, stable isotope ratio analysis (SIRA), mineral element fingerprints, spectroscopy and mass spectrometry metabolomics, and emerging sensors. The authors then discuss in some detail why some of these approaches are more – or less – applicable for different types of tea.
They argue that origin traceability of tea is not merely an analytical chemistry issue. The essential differences in the processing techniques of the six major tea types (green, white, yellow, oolong, black, and dark) determine that the applicability boundaries of the same traceability technology may vary significantly among different tea types.
- The high-temperature kill-green process in green tea deactivates the polyphenol oxidase activity, preserving the original chemical fingerprint of the fresh leaves to the greatest extent.
- White tea undergoes the least processing intervention, and theoretically has the best traceability.
- The impact of the micro-fermentation process on the chemical profile of yellow tea remains to be systematically evaluated.
- Oolong tea’s withering and roasting processes result in a fermentation degree ranging from 10% to 70%, making the complexity of the chemical fingerprint’s interference from processing the most among the six major tea types.
- The full fermentation process in black tea converts a large amount of catechins into theaflavins and thearubigins, deeply reshaping the primary metabolite profile.
- The post-fermentation of dark tea, driven by microbial communities, triggers biochemical transformations that can last for months or even years, with the origin signal highly intertwined with factors such as the degree of fermentation, aging years, and tree age
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