## 3 Results and Discussion
### Aroma Volatile Compounds
However, no literature on green tea volatiles reported this compound and no information regarding the aroma or flavor characteristics was found. 2-Ethyl-1-hexanol was detected in the _Daehan Ujeon Wild_ sample at the second brew and in the _Myoungjeon_ sample at the fifth brew only. The concentrations of the compound in these two samples were at 2.32 \(\mathrm{\SIUnitSymbolMicro g}\)/L and 4.52 \(\mathrm{\SIUnitSymbolMicro g}\)/L, respectively. It was previously reported in a Japanese green tea [15] but no other literature has reported 2-ethyl-1-hexanol in green teas. It has a mild, oily, sweet and slight rose fragrance [37]. Benzyl alcohol (benzenemethanol) was found in a few brews of the _Daehan Ujeon Wild Tea_ sample and the _Daehan Ujeon_ sample. It has a faint aromatic odor [37] and has previously been found in Korean tea [38]. Phenethyl alcohol (benzeneethanol) has a floral and rose odor [37] and was found in the second brew of the _Ujeon Okro_ sample. Linalool has been reported in green tea by many other researchers [15, 38, 39, 40]. As expected, it was detected in all five samples except _Myoungjeon_ and was present in more than three consecutive brews in the _Daehan Ujeon_, _Illohyang_, and _Ujeon Okro_ samples. Though, the trend of changes in the concentration for repeated brews differed among these samples. Linalool's odor is similar to bergamot oil [37] and citrus [41]. It is detectable at as low as 0.087 \(\mathrm{\SIUnitSymbolMicro g}\)/L and recognizable at as low as 0.17 \(\mathrm{\SIUnitSymbolMicro g}\)/L [41], which both are lower than our findings ranging from 3.16 \(\mathrm{\SIUnitSymbolMicro g}\)/L to 15.10 \(\mathrm{\SIUnitSymbolMicro g}\)/L. Geraniol is another terpene alcohol and has a geranium odor [37]. It was found in the _Illohyang_ and the _Ujeon Okro_ samples. The concentrations of geraniol in these two samples were the highest in the second brew and declined as they were brewed repeatedly. Geraniol has been found commonly in green teas [38]. Its thresholds were reported as 1.1 \(\mathrm{\SIUnitSymbolMicro g}\)/L for detection and 2.5 \(\mathrm{\SIUnitSymbolMicro g}\)/L for recognition [41]. Nonanal was present in all six samples in our study. However, the concentrations of nonanal in each brew did not have any perceivable trend. It has a tallow, fruity [42], strong, fatty odor [37], citrus-like and soapy [41]. Its detection threshold was reported as 2.8 \(\mathrm{\SIUnitSymbolMicro g}\)/L and its recognition threshold was reported as 8.0 \(\mathrm{\SIUnitSymbolMicro g}\)/L [41]. The nonanal was reported in a Korean commercial green tea made with tea leaves harvested in July and roast-processed [43] but was not reported in the other studies with Korean green teas [10, 11]. Benzaldehyde was only detected in the first brew of the _Myoungjeon_ sample. It is an aromatic aldehyde and has an almond odor [37] and commonly is used in artificial cherry flavor to provide a strong fruity note. The benzaldehyde was commonly found in green teas from Korea in previous literature [10, 11, 43]. The benzaldehyde may not be detected in more of our samples because of the sample preparation and the extraction technique. In the current study, brewed green tea liquor was used as a sample and the volatile compounds were extracted using SPME, which can detect the concentrations ranging from pg/g (ppt) to \(\mathrm{\SIUnitSymbolMicro g}\)/g (ppm). The concentration of benzaldehyde in the second brew of the _Myoungjeon_ sample was 0.90 \(\mathrm{\SIUnitSymbolMicro g}\)/L, which is 0.90 ppb. Phenylacetaldehyde (benzeneacetaldehyde) was present in the first brews of the _Myoungjeon_ and the _Ouksu_ samples. It is an aromatic aldehyde and has a pungent, green, hyacinth-like, apricot, and berry-like flavor [37]. 4-Methyl-3-pentene-2-one was detected in the _Myoungjeon_, _Ujeon Okro_ and _Ouksu_ samples. The concentrations ranged between 1.42 and 3.81 \(\mathrm{\SIUnitSymbolMicro g}\)/L. It has a sweet, fruity odor and it is somewhat water soluble [37].