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The present study confirmed the presence of a fluorescent component (Ex490 nm/Em520 nm) in pu-erh tea using a three-dimensional fluorescence spectrophotometer. This component was detected at small quantities in other teas such as green tea, oolong tea and black tea. The compound was fractionated from hot-water extracts of pu-erh tea using liquid-liquid distribution and column chromatography methods. Fluorescence analysis and element assay suggested that the compound was a highly polar and high-molecular-weight complex, similar to humic substances. The compound is stable and the dose-response curve on fluorescence intensity showed linearity for quantitative estimation. In addition, teas with longer aging periods and higher prices showed stronger intensity. These results suggest that measurement of fluorescence in this region is useful for quality determination of pu-erh tea and in distinguishing it from other fermented teas.
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Yamazaki et al. (2013) studied this question.
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