This study analyzes the chemical composition of green tea, white tea, yellow tea, oolong tea and black tea with respect to extraction temperature and time. The optimum extraction conditions for these teas were determined by assessing the chemical composition of tea brewed at different temperature (50, 60, 70, 80℃) and extraction times (1, 3, 5, 10 minute). Catechins contents were the largest at 5 minutes and generally declined by 10 minutes. Green tea catechins contents were highest when brewed at 70℃ and besides other teas a change of the trend variation at 70 and 80℃. These temperatures did not extract theaflavins in green tea. Extract temperature and time did not significantly affect theaflavins content of white tea, yellow tea, and oolong tea. Black tea, however, was noticeably dependent on extract conditions, which were most effective at 70℃, brewed for 5 minutes. Caffeine content of green tea, yellow tea, and oolong tea was highest at 5 minutes, but temperature did not appear to affect the content. White tea and black tea caffeine content was highest when brewed at 70℃ for 5 minutes. Theobromine content of green tea, yellow tea, oolong tea, and black tea did not show major differences between the study times or temperature, though the content in white tea increased with higher temperatures when brewed for 5 minutes. The extraction of phenolic compounds increased until 5 minutes, and showed not further increase at 10 minutes. Antioxidant capacity of green tea, white tea, and yellow tea were maximized at 70℃ for 5 minutes or 80℃ for 3 minutes, while oolong and black tea were reached maximum antioxidants at 70℃ for 5 minutes. In general, to optimize the beneficial chemical content of brewed tea, a water temperature of 70℃ for 5 minutes is recommended.

This study was carried out to measure the contents of moisture, crude ash, crude fat, total amino acid, with amino acid composition, vitamin C, β-carotene, vitamin E, total catechins, EGCG, EGC, ECG, EC, GA, caffeine, theobromine and theophylline of the green tea I, II, III, oolong, and black tea. The content of crude fat of green tea I, II, III, oolong, and black teas was 1.1, 2.5, 4.9, 0.8 and 1.2% respectively, total amino acid content was 0.87, 0.78, 0.60, 0.63 and 1.05% respectively, and theanine content was 0.52, 0.48, 0.31, 0.41 and 0.61%, respectively. Total amino acid content of green tea increased in the order of green tea I $gt; green tea II $gt; green tea III, and among the teas, the content of theanine was the highest in the amino acids present. The content of vitamin C of green teal, II, III, oolong, and black tea was 101.6, 87.5, 95.9, 99.1 and 108.0 mg%, respectively, β-carotene content was 270, 268, 481, 80 and 181 ppm, respectively. Among the α-, β-, γ- and δ-tocopherol, the content of α-tocopherol was the highest in vitamin E present, and β- and δ-tocopherol were not detected in the samples of green teal, II, III, oolong, and black teas. The total catechins of green teal, II, III, oolong, and black teas was 10.5, 10.4, 7.2, 8.4 and 1.8% respectively, and among them, EGCG content was the highest. The content of EGC increased in the order of green tea I $gt; green tea III $gt; green tea II $gt; oolong tea $gt; black tea. The contents EGCG and ECG increased in the order of oolong tea $gt; green tea I $gt; green tea II $gt; green tea III $gt; black tea, and the highest contents of EGCG and ECG were observed in the samples of oolong tea. The content of GA was 0.01, 0.02, 0.05, 0.13 and 0.31%, respectively, and the highest contents of GA, caffeine and theobromine were observed in the sample of black tea. The highest content of theophylline, however, was observed in the sample of green tea I.

The extraction yield of MeOH extract of green teas, oolong tea and black tea were 3 to 5, 4 to 5, and 5 to 7 fold higher than those of EtOH and EtAC extract, respectively. The amount of total catechins of EtAC extract of the black tea, and of the green teas and oolong tea were three- and two-fold higher than that of EtOH or MeOH extract of the corresponding teas, respectively. The antioxidative activities of EtOH, MeOH and EtAc extract were considerably higher than that of BHT and dl-α-tocopherol at 200 ppm level. The antioxidative activities of EtOH and MeOH extract at 200 and 500 ppm level, and of EtAc extract at 200 ppm level varied depending on the type of tea as follows : green tea I $gt; green tea II $gt; green tea III $gt; oolong tea $gt; black tea. The antioxidative activity increased as the content of EGC increased. But the antioxidative activity of MeOH extract at 1000 ppm level, and of EtAc extract at 500 and 1000 ppm level were not affected by the content of EGC and EGCG.

우롱차의 에탄올 추출 특성을 조사하기 위하여 추출농도 및 온도별로 우롱차의 품질에 미치는 유효성분들을 분석, 조사하였다. 우롱차엽의 에탄올 추출물은 추출시 80~85℃, 50%이상의 에탄올 농도에서 대체적으로 높은 수율을 나타내었다. 추출물의 유효성분 분석에서 유리당은 sucrose가 37.2~55.0 mg/100 g로 가장 함량이 많았으며 반면에 arabinose는 3.3~5.6 mg/100g로 가장 낮은 함량을 나타내었다. 에탄올 추출물의 유기산 함량은 furmaric acid가 0.2477~0.7842 mg/g, citric acid가 0.2047~0.6204 mg/g malic acid가 0.1619~0.4382 mg/g로 주요 유기산으로 나타났다. 유리아미노산은 aspartic acid, glutamic acid, serine, histidine 등 15종류가 나타났으며 그 중에서 proline이 0.693~1.681 mg/g으로 가장 많이 나타났고 tyrosine, glutamic acid, valine, aspartic acid 등도 다른 유리아미노산보다 많은 양을 보였다. 추출조건에 따른 탄닌의 함량은 물과 25% 에탄올농도에서 38.6, 38.5 μg/100 g을 나타냈고 추출용매의 농도가 높을수록 탄닌의 함량은 낮아져 95% 에탄올 농도에서는 24.2 μg/100 g을 나타내었다. 카페인의 함량은 추출용매의 차이에도 뚜렷한 변화를 나타내지 않았고 그 함량은 12.65~14.08 mg/g이었으며 ascorbic acid의 함량은 물과 25% 에탄올농도에서 6.95 μg/g과 6.50 μg/g을 나타냈고 추출용매의 농도가 높아질수록 ascorbic acid의 함량은 낮아져서 95% 에탄올에서는 2.78 μg/g을 나타내었다. 추출용매의 농도에 따른 관능검사 결과 떫은 맛과 쓴맛이 전체적인 기호도에 가장 높은 상관계를 나타내었으며 에탄올 농도를 25%로 하여 추출한 우롱차의 전체적인 기호도가 가장 높게 나타났다.