Friday, July 18, 2008
Posted by 醉茶生 at 10:38 PM | Comments (1) | Permalink
Categories: Tea Green

Green tea has more recently become popular in the West because of its high anti-oxidant content (polyphenols), which is reputed to protect against a variety of ills, including heart disease and cancer. To this end, many supermarkets now stock at least a few varieties of green tea.

Most green teas sold in the West are heavily flavoured with fruit or flower, largely with the intention of masking the smell of the tea. If you are used to drinking black tea, then the savoury, meaty taste of green tea is startling and may put you off.

Chinese green tea and Japanese green tea are different beasts. They are similar in that heat is applied very early in processing to stop enzymes from breaking down the phenolic compounds in tea (the all-important anti-oxidant bit). In Chinese tea, the heat is applied in a hot metal pan (much like a wok), which removes some of the colour and imparts a savoury fragrance very reminiscent of meat (which comes from pyrazines and pyrroles). In Japanese tea, the heat is applied as steam, which preserves much of the grassy taste of the leaves, allows it to retain a fresh green colour even when dried, and is also responsible for the distinctive seaweed flavour of Japanese green tea (dimethyl sulphide).

Tea contains a unique amino acid called theanine, which is able to cross into the brain and produce feelings of relaxation and improve cognition. Some of it breaks down to glutamic acid, which is a flavour enhancer. Tea also contains guanosine monophosphate and inosine monophosphate, which are both flavour enhancers as well, and serve to further intensify the savoury taste of green tea.

Lu K, Gray M, Oliver C, Liley D, Harrison B, Bartholomeusz C, Phan K, Nathan P (2004). “The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans”. Hum Psychopharmacol 19 (7): 457–65. doi:10.1002/hup.611. PMID 15378679.
Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB (2008). “The effects of l-theanine, caffeine and their combination on cognition and mood”. Biol Psychol 77 (2): 113–22.

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