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강정숙 제주대학교 방사능이용연구소 2003 연구보고 Vol.17 No.-
The present study was conducted to compare antioxidant activity of green tea and related other common teas according to growing, processing and brewing by examining radical scavenging activity using DPPH (2,2 Diphenyl 1-picryl hydrazyl). SC_(50) of epigallocatechin gallate (EGCG) for 0.1mM DPPH radical were 5.5μM or 4.2㎎/ℓ by weight, then catechin, 14μM or 2.5㎎/ℓand vit C, 22μM or 3.9㎎/ℓ respectively. Okro tea powder of 24.2㎎/ℓ or green tea powder of 25.2㎎/ℓ was used to reach SC_(50) for 0.1mM DPPH. One serving of 2g green tea provides antioxidant activity equivalent to 109∼147㎎ EGCG, 130∼182㎎ catechin or 142∼168㎎ vit C. Teas from the first spring flush had the highest radical scavenging activity when compared with later harvest green tea grown in the same region, but there virtually is no difference by the harvest time. Chinese green tea, Younjung had the highest antioxidant activity among other green teas tested providing antioxidant capacity equivalent to 168㎎ EGCG or 188㎎ vit C per 2g serving, but partially fermented Chinese teas had much lower antioxidant activity than any green tea tested. Black tea which is fully fermented showed as strong antioxidant activity as green teas when compared in teabag. One teabag of green teas from market provided antixidant effect equivalent to 50∼85㎎ EGCG, 70∼105㎎ catechin or 60∼95㎎ vit C. Teas made of persimon, pine needle, mulberry had comparatively low antioxidant effect of 2.5∼3.5㎎ EGCG or 15∼20㎎ vit C per teabag. The third brewed green gea still had enough antioxidant activity, while tea from teabag brewed for 3min or 5min did not have any difference in their antioxidant activity. In conclusion, reen tea from the first harvest had more antioxidant activity and okro which is grown under shade had more or at least as much antioxidant activity as the green tea grown in the same region. Partially fermented Chinese teas were low in antioxidant effect while fully fermented black tea had strong antioxidant ctivity. More systemic studies are needed to clarify the changes in tea catechins in relation with fermantation process.