TungTing and TieGuanYin (Iron Goddess) are two Taiwan oolongs noted for its extensive post-production roasting. For oolong teas, tea leaves may undergo different degrees of roasting, or even none at all. Generally green and black teas are not roasted. That white substance, as you can guess, was caffeine. When I was in Taiwan observing tea makers during the roasting process, it was not uncommon to see a thin layer of white powdery and threadlike substance on top of roasting ovens. After roasting, water content in tea leaves is reduced from 5-6% to 2~3%. Caffeine dissolves readily in hot water and evaporates away with water during roasting. However, post-production roasting can make a big difference. (4) Production Process: S tudies have shown that oxidation levels do not significantly affect caffeine level. (3) Cultivation methods: Cultivated plants tend to have more caffeine than those growing in the wild. (2) Harvest season: The caffeine amount for the four seasons, from highest to lowest, are: for matcha, tea leaves are grounded into fine powder and consumed), the caffeine intake is much higher compared to using the leaves to brew tea. Caffeine amount is even lower in tea stems or stalks – about 10% ~ 50% of that in leaves. If the tea leaves are actually consumed (e.g. According to a study by Taiwan’s tea research agency, the first leaf (closest to the bud) contains almost 40% more caffeine compared to the second to the sixth leaf (away from the bud). (1) Parts of the tea plant plucked and used: Tender young leaves contain more caffeine than mature leaves. 3 It also functions as part of the plant's defense system against the external environment.įactors affecting the caffeine level in tea leaves include: It contributes to a tea’s bitter taste and overall flavor. 2 Caffeine is a stimulant that has a bitter taste but no smell. It accounts for 3~5% of tea leaves’ total solid contents. Caffeine in tea, also known as theine, is one of three alkaloids 1 contained in tea leaves.
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