Aroma Composition of Oolong Tea and Black Tea by Brewed Extraction Method and Characterizing Compounds of Darjeeling Tea Aroma

Volatile component of various brewed oolong teas and black teas were analyzed by gas chromatography (GC) and gas chromatography/FTIR spectrometry/mass spectrometry. The GC pattern of brewed tea extracted by dichloromethane (brewed extract) differs greatly from the GC pattern of the extract prepared by simultaneous steam distillation and extraction method (SDE). The brewed extract includes higher amounts of acids, aromatic alcohols, and monoterpenediol and lower amounts of monoterpene alcohols than the SDE extract. The Darjeeling brewed extract, which has a more complicated aroma pattern, consists of four linalool oxides, linalool, geraniol, hexanoic acid, benzyl alcohol, 2-phenylethanol, trans-geranic acid,(E)-2-hexenoic acid, (Z)-3-hexenoic acid, and 2,6-dimethyl-3,7-octadiene-2,6-diol. The Darjeeling SDE extract consists of seven main components which include geraniol, linalool, four linalool oxides, and methyl salicylate. The brewed extract of Chan Pin oolong (red oolong tea), which is similar in aroma to Darjeeling and is made from tea leaves infested with green flies (Emposca flavescens) in the same way as Darjeeling, contains very high amounts of 2,6-dimethyl-3,7-octadiene-2,6-diol. This compound appears to be the precursor of 3,7-dimethyl-1,5,7-octatrien-3-ol and to be the most important factor in Darjeeling tea flavor