## 2 Results and Discussion
### Volatile Compounds in Prepared Green Teas
#### 2.1.2 Compounds Present  
Twenty green tea samples contained linalool, which has a \"light, refreshing, floral-woody with a faintly citrusy note\" [33]. Concentrations of linalool in final products range from 2 to 10 \(\upmu\)g/L in candy and beverages and could be as high as 40 \(\upmu\)g/L in meat products [33]. Concentrations of linalool in the green tea samples in this study were much lower and ranged from 0.27 ng/kg to 3.34 ng/kg. These were 1,000 times lower than orthonasal and retronasal thresholds, which are 5-6 \(\upmu\)g/L and 1.5 \(\upmu\)g/L in water, respectively [31]. Seventeen green tea samples had nonanal and its concentration varied from 0.22 ng/kg to 1.32 ng/kg. Nonanal has a tallowy and fruity odor [31] and its typical concentrations in final products range from 0.2 to 6 \(\upmu\)g/L [33]. Nonanal is widely reported in green tea [12; 34; 35]. However, a direct comparison of concentrations between the samples in previous research and our green tea samples is not possible because only relative quantities have been reported in the form of peak area percentages. The threshold of nonanal is \(\sim\)1 \(\upmu\)g/L for orthonasal evaluation [31]. Eleven green tea samples had benzaldehyde at concentrations lower than 1 ng/kg. Benzaldehyde has a dominantly sweet aroma of freshly crushed almonds; it typically is used in artificial cherry flavorings. The typical concentrations in final products usually range from 150 to 160 \(\upmu\)g/L [33]. Benzaldehyde has been identified in green tea by many researchers [7; 8; 12; 21; 34; 36] evaluating samples from the Azores, China, Japan, Korea and Taiwan. Ten samples had \(\upbeta\)-ionone in concentrations ranging from 0.25 ng/kg to 1.21 ng/kg. \(\upbeta\)-Ionone has a violet-like odor and can be detected at concentrations as low as 0.007 \(\upmu\)g/L [31] in water. Typical concentrations in final products range from 1 to 10 \(\upmu\)g/L [33]. \(\upbeta\)-Ionone is commonly found in green teas [7; 8; 12; 24; 37; 38] with peak areas ranging from 1.36 to 4.49% in Japanese green teas [12]. Hexanal was found in eight samples at concentrations lower than 1 ng/kg. Other researchers found hexanal in green teas in trace or small amounts [7; 12; 36]. The aroma of hexanal has been described as being similar to freshly cut grass and unripe fruits in extreme dilution. However, hexanal has been shown to change character completely, from green to beauty, which combined with other compounds [39]. Its concentrations in final food products generally is given as between 1 \(\upmu\)g/L and 5 \(\upmu\)g/L [33]. The threshold of hexanal ranged from 4.5 \(\upmu\)g/L to 50 \(\upmu\)g/L for orthonasal evaluation and from 10.5 \(\upmu\)g/L to 16 \(\upmu\)g/L for retronasal evaluation [31], which is at least 10\({}^{4}\) times higher than the concentrations found in any of the samples in our study. Even though the concentrations are lower than threshold, hexanal may contribute to aroma in combination with other volatile compounds [39] as might occur in green tea. Geraniol, a terpene alcohol, was present in seven samples at concentrations below 1 ng/kg. It has been found in green tea by other researchers [7, 8, 12, 36, 37, 38] and is a colorless, oily liquid with a flowery, rose-like aroma [33]. The orthonasal threshold reported for geraniol varies from 5 to 75 \(\mu\)g/L in water [31] and concentrations of geraniol in the samples in this study were well below the reported threshold values. Seven green teas had jasmone in concentrations that ranged from 0.31 ng/kg to 1.13 ng/kg. Jasmone has a floral odor [33] and has been found in many green tea samples [7, 12, 34, 38]. Korean green teas manufactured from leaves picked in April were found to have more jasmone than the samples harvested in June [7]. A similar trend was found in our study in that Korea 2, 3 and 4 (all of which were picked in April) had jasmone but the compound was not detected in the Korea 1 sample (which was picked in May). Jasmone was not detected in most of the green tea samples in our study including Japan 5 (_Gyokuro_).