Flavor is one the most important factors to determine the quality of beverages. Tea aroma, especially floral aroma liberated from brewed oolong tea and black tea, is so attractive. This study covers the molecular basis of the floral aroma formation during the tea processing. Previous work demonstrated the tea aroma precursors of geraniol, linalool, etc. as β-primeverosides (6-Ο-β-D-xylopyranosyl-β-D-glucopyranosides) from the tea leaves (Camellia sinensis var. sinensis cvs. Shuixian and Maoxie) which can be processed to oolong tea. We have also purified β-primeverosidases from fresh leaves of cv. Yabukita for Japanese green tea, cv. Shuixian for oolong tea and a cultivar of C. s. var. assamica for black tea. The molecular weight of each enzyme was shown to be 60,500, 60,200 and 60,300 by TOFMS, respectively. The enzymatic characteristics (optimum temperature, 45 °C; stable temp., 40-45 °C; optimum pH, 4; pH stability, pH 3-5; specific activity, 0.90-0.99 unit/mg) were very similar to each other. The enzyme was confirmed to effectively hydrolyze the aroma precursors, β-primeverosides as well as 6-O-β-D-apiofuranosyl-β-D-glucopyranoside, into disaccharides and each aglycon without further hydrolysis. Most of the alcoholic tea aroma, which contribute to the floral tea aroma, are primarily stored as disaccharide glycosides (β-primeverosides and 6-O-β-D-apiofuranosyl-β-D-glucopyranosides) and generated by the action of a specific enzyme, β-primeverosidase, during the fermentation process of tea manufacturing.
fermentation, tea, primeverosides, β-primeverosidase
Publication DOI: 10.1021/bk-2000-0754.ch033Publisher: American Chemical Society
Editors: Parliment TH, Ho C-T, Schieberle P
Institutions: Institute for Chemical Research, Kyoto University, Uji, Japan
Methods: enzymatic digestion, CC
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