Green tea is made solely with the leaves of Camellia sinensis that have undergone minimal oxidation during processing. Green tea originates from China and has become associated with many cultures in Asia from Japan and South Korea to the Middle East.
Recently, it has become more widespread in the West, where black tea is traditionally consumed. Many varieties of green tea have been created in countries where they are grown. These varieties can differ substantially due to variable growing conditions, horticulture, production processing, and harvesting time.
Over the last few decades green tea has been subjected to many scientific and medical studies to determine the extent of its long-purported health benefits, with some evidence suggesting that regular green tea drinkers have lower chances of heart disease and of developing certain types of cancer.
Although green tea does not raise the metabolic rate enough to produce immediate weight loss, a green tea extract containing polyphenols and caffeine has been shown to induce thermogenesis and stimulate fat oxidation, boosting the metabolic rate 4% without increasing the heart rate.
According to a survey released by the United States Department of Agriculture in 2007, the mean content of flavonoids in a cup of green tea is higher than that in the same volume of other food and drink items that are traditionally considered of health contributing nature, including fresh fruits, vegetable juices or wine. Flavonoids are a group of phytochemicals in most plant products that are responsible for such health effects as anti-oxidative and anticarcinogenic functions. However, as a tea information site points out, the content varies dramatically amongst different tea products, basing on the same USDA survey.
Steeping
Steeping is the process of making a cup of tea; it is also referred to as brewing. Generally, two grams of tea per 100ml of water, or about one teaspoon of green tea per five ounce cup, should be used. With very high quality teas like gyokuro, more than this amount of leaf is used, and the leaf is steeped multiple times for short durations.
Green tea steeping time and temperature varies with different tea. The hottest steeping temperatures are 81°C to 87°C (180°F to 190°F) water and the longest steeping times two to three minutes. The coolest brewing temperatures are 61°C to 69°C (140°F to 160°F) and the shortest times about 30 seconds. In general, lower quality green teas are steeped hotter and longer, while higher quality teas are steeped cooler and shorter. Steeping green tea too hot or too long will result in a bitter, astringent brew, regardless of the initial quality. It is thought that excessively hot water results in tannin chemical release, which is especially problematic in green teas as they have higher contents of these.
High quality green teas can be and usually are steeped multiple times; two or three steepings is typical. The steeping technique also plays a very important role in avoiding the tea developing an overcooked taste. Preferably, the container in which the tea is steeped or teapot should also be warmed beforehand so that the tea does not immediately cool down. It is common practice for tea leaf to be left in the cup or pot and for hot water to be added as the tea is drunk until the flavor degrades.
Article source: Wikipedia, the free encyclopedia
For more reading on the benefits of green tea, go here:
http://www.umm.edu/altmed/articles/green-tea-000255.htm
http://www.xuantea.com/info/tea-benefits/i37/tea-benefits.aspx