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• Tea Bags : Scientifically speaking, infusion tea bags are not compatible with brewing green tea for health. To make infusion tea bags, the manufacturers use dust-grade tea leaves or reduce the relatively intact tea leaves to duct-grade sizes for filling the tea bags. The fragmented tea leaves in dust size have a large total cut surface exposed to the air which would facilitate the oxidation process of the antioxidants in the tea leaves. Therefore, the tea in infusion bags generally has very low levels of the antioxidant EGCG. In addition, in order to prevent the tea bag tissue from disintegrating during tea brewing in hot water, the tissue has been treated by a cross-linking agent(s) containing formaldehyde derivatives. It has been shown that some formaldehyde-like molecules are released from the tea bag during hot water steeping in the tea cups. These formaldehyde-like molecules may not be toxic per se, but their effect on the bioactivity of the green tea is unclear. Therefore, it is inappropriate to put 710EGCG® green tea into infusion tea bags.

• Loose Leaf Tea : All green teas consumed for health reasons must be in the form of loose leaves, and the leaves must be mechanically damaged before drying. The scientific reasoning is as follows. In a natural tea leaf (see illustration for Fresh unprocessed tea leaf), the tea catechins, like the EGCG molecules, are stored in small vesicles formed by membranes in the spongy mesophyll. These vesicle membranes must be broken for the antioxidants to be extracted into the hot water during tea brewing. In a properly processed tea leaf (see illustration for Properly processed tea leaf), the membranes of the vesicles in the mesophyll are broken, but the two surface epidermis layers are still intact so that the antioxidants released from or still in the broken vesicles are not squeezed out onto the surface of the dried tea leaves, as in a poorly preserved tea leaf, where the antioxidants on the tea leaf surface would easily be oxidized (see illustration for Poorly processed tea leaf). The experienced tea workers in the Chinese tea industry refer to this technical blunder as “losing the tea juice."

• Black Tea : The Portuguese sailors were the first Europeans to trade tea in China in the 1500’s AD. The first shipment of tea to Western Europe was made by the Dutch East India Company in 1606. They were all green teas when the merchandise was loaded on board in Amoy, a major seaport in Southern China. The term “Orange Pekoe” referred to a first-grade green tea imported to Europe by a company bearing the royal family name of the Dutch monarch- “Oranje”. The word “Pekoe” which now means black tea in the English dictionaries is the phonetic spelling of the Amoy dialect word “white fine hair” or “down”, still used in China among the tea traders to describe the appearance of the dry green tea leaves composed of the buds and the first two young leaves. However, after a long sea journey with constant agitation over the choppy warm ocean water in humid hot weather, the high quality “Pekoe” green tea were largely molded and had turned “black” with its characteristic bitter taste as a result of oxidation and degradation when the ship arrived in Holland. The Europeans would put sugar and milk into the bitter tea from China, which had turned black. This is the origin of black tea, a European invention.

• Green Tea : Green tea means non-oxidized or unfermented tea leaves. When tea first became a commodity in Tang Dynasty (617-907 AD), freshly plucked tea leaves were smashed to brew tea. The upper-class intellect elite had their own tea garden as depicted in the poem written on a classic Ming dynasty Chinese painting titled “Drinking Tea” (By Tang Yin, ca. 1,500 AD) now on display in the Palace Museum, Beijing. By definition, all teas in ancient China were 710EGCG® green tea by our definition.

  As tea became a commodity for trading, it was necessary to preserve the quality of the fresh tea leaves by a brief heating and drying process for transportation and for storage. The fresh tea leaves must undergo an initial heat treatment for quality preservation. Now, we know its purpose was to inactivate the polyphenol oxidase in tea leaves to stop the oxidation process in order to preserve the antioxidant tea catechins. The tea leaves which were not processed immediately would turn brown, just like a sliced apple undergoing discoloration when exposed to the air. The tea leaves which became brown were dried at high temperature and pressed into cakes and bricks as salvage products, which were considered of low-grade teas and were mostly sold to the minority Chinese living in the North/West or to foreign traders. Historically, “tea” always referred to green tea in the ancient China and in Japanese until now.

• Jasmine Tea : Jasmine tea is usually a green tea of uncertain quality with added dried jasmine flowers. The flavor and fragrance of the tea drink are determined by the jasmine flowers, rather than by the tea leaves. The EGCG contents are usually low although jasmine tea is marketed as green tea because it has not been “fermented."

• White Tea : White tea is a poorly defined category. The term “white tea” first appeared in a monograph entitled “A Grand Overview on Tea” which was written by emperor Hui Zhong of the Song Dynasty in 1107 AD. The emperor mistakenly thought a weakened mutant of tea plant with delicate light-colored leaves which had lost its ability to reproduce to be a rare species of tea trees. Nowadays, white tea is produced from the same tea leaves as those used for green tea, black tea and oolong tea, but without heat inactivation. The manufacturing methods vary. One popular protocol of production is to let the fresh tea leaves air-dry at 28-30º C in 65-70% relative humidity for 34-38 hours to reduce their water contents to 14-16% in dry weight. Then the leaves are hand-selected and further dried in low heat or under the sun. Since the polyphenol oxidase of the tea leaves has not been inactivated, the tea catechins in white tea undergo continuous oxidation at uncontrolled rates during production and storage. Its residual EGCG levels vary widely and are generally very low in the samples purchased on the market.

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