Identification of Key Odorants in Semi-Fermented Tea Made in Taiwan by Using Solvent-Assisted Flavor Evaporation Apparatus under High Vacuum and Application of the Aroma Extract Dilution Analysis

Summary The semi-fermented tea process including withering and shaking of fresh tea leaves has come to be taken in to make a fragrant tea in Japan. Elucidation of the key odorant in the semi-fermented tea is essential for the manufacturing and quality control. The semi-fermented tea has been manufactured flourishingly in Taiwan. Therefore, this study has revealed the key odorants in the semi-fermented teas including pouchong tea, oolong tea and oriental beauty made in Taiwan. An aroma extract of the semi-fermented tea was prepared by using the solvent-assisted flavor evaporation (SAFE) technique (10 -3 Pa). An aroma extract dilution analysis applied to the volatile fraction revealed 3-mercapto-1-hexanol, jasmine lactone and (Z)-methyl jasmonate were the most prevalent odorant in the pouching tea and oolong tea. On the other hand, two odorants of phenylacetaldehyde and β-damascenone were the most prevalent in oriental beauty. The aroma extract isolated by using the SAFE unit would be about the same with the ingredient composition when drinking. Hence, the obtained result would be good contribution to the improvement of manufacturing technology, as well as its quality control of the semi-fermented tea.