| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 101 === It is well known that the flavor of tea is closely associated with the tea pot that the tea soup was made in. Tea pot material is believed to have effect on the sensory and nutritional performance of tea soup, but to this date, there has been no scientific explanation about how tea pot material can make such an effect on tea soup. The purpose of this study was to evaluate the adsorption and release behavior of caffeine and 4 catechins (EGC, EGCG, EC and ECG) by 7 commonly used tea pot materials including Zisha, Zhuni, red clay, ceramic, stainless steel, glass and plastic, in an attempt to find possible explanations on how the materials affect the sensory performance of the tea soup. When caffeine at 250 μg/mL was in a pot, the highest adsorption at 10 minute was by Zisha pot (3.2%) while the lowest was by glass and plastic pots (1.1%). Higher adsorption could be achieved (up to 10%) by Zisha, Zhuni, red clay and ceramic pots after 24 hours rat. At the time interval of 10 minute and 10~60 minute, all tea pots showed no difference in adsorption, but adsorption rate started increasing at 3~9 hours, with higher magnitude in Zhuni and red clay pots. Between 9~24 hours, the adsorption rate increased by another 2~3%. For the 4 catechins, the adsorption by Zisha, Zhuni and red clay pots was about 0.5~1.6% at one minute. After 5 minutes, the adsorption started increasing in all pot materials with the highest adsorption found in EGC (except for plastic and Zhuni pots). At 10 minutes, Zisha, Zhuni and red clay adsorbed the 4 catechins at around 4%, which elevated to 10~13% at 24 hours. Red clay, ceramic, stainless steel and glass pots adsorbed more EGC whereas Zisha and Zhuni pots adsorbed more EC. Comparison by two time intervals, the first 10 minute and 9~24 hours, the adsorption of catechins doubled in all pot materials and the adsorption of EGCG increased by 3~5 times in Zisha, Zhuni, red clay and ceramic pots. When caffeine and catechins coexisted in a tea pot, competition between caffeine and catechins were observed except for in the plastic and glass pots. At the presence of catechins caffeine adsorption decreased in Zisha, Zhuni and stainless steel while it elevated in red clay and ceramic pots. As for the releasing behavior, after 24 hours of adsorption, red clay and Zisha released caffeine at the level 3.5μg/mL and 0.9μg/mL, respectively. Only Zisha released detectable EGCG for up to 0.3μg/mL at 10 minutes, however, as the time passes, the catechin level in Zisha gradually decreased to 0.05μg/mL at 24 hours, suggesting the released EGCG was re-adsorption to the pot. In conclusion, of the 4 tea pot materials, Zisha, Zhuni and red clay adsorbed more caffeine and catechins than the other 4 pots, the effect may partially contribute to the lowering of the sensitivity to bitter taste. When caffeine and catechins were both present, only Zisha showed significant difference in decreasing EC. The current study revealed the association between caffeine and catechins and adsorbing effects of common tea pot materials and proved that tea pots can give rise to different tastes.
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