Puerh Teas (Hei Cha):
Puerh is a fermented dark tea produced mainly in Yunnan province (named after the town of Puerh), China. This tea is made by aging for upwards of 3 years, or by a relatively new process of speed fermenting. These processes could also be referred to as "raw" (natural), and "cooked" (cultured to quicken fermentation time). Generally, the natural method is preferred, though many can truthfully not tell the difference. Some evidence suggests that "cooked" puerh contains more medicinal value, however many tea connoisseurs prefer the flavour produced from "raw" puerh". Technically, only tea produced in this way (secondary fermentation), that is made in the Yunnan province can be called Puerh, however teas made using the same methods are produced all over, with the most famous being Xishuangbanna.
The tea starts as a mostly unoxidized green tea, processed from a large leaf variety of Camellia sinensis (C. sinensis var. assamica), or a different large leafed cultivar known as Da Ye or Qimau (suggested to be a new species, C. taliensis). found growing in the mountains of Yunnan. In the highest quality puerh teas, the leaves of a very specific set of old trees (100+ years old) in the Yunnan province are used. The tea is then semi sun dried, and pan fried to arrest the enzyme activity and prevents oxidation. Once this is done the leaves are rolled, rubbed, and left in the sun to further dry. Then, the tea goes under a secondary oxidation process and fermentation caused both by organisms growing on the leaves (bacteria, and fungi), as well as some oxidation through enzymes. This can occur in both loose leaf form, or pressed form, though it ferments quicker as loose leaf tea. The pressed "cakes" last longer, and improve with age. Generally puerh is left to ferment for 10-25 years, while some are suggested to be 50 years old or older and can be worth tens of thousands of dollars. The concept of pressing teas into cakes is not exclusive for puerh, it was a way to make tea last longer wether it was oolong, black, or green, however it is common practice for most puerh to be found this way.
Colour in puerh teas varies greatly from green (younger teas), to dark brown or red (older teas). The flavour changes drastically as well, becoming smoother, more earthy, and mellow, as well as losing its astringent and grassy flavours as it ages. Chemical makeup changes over this process as well. Fermented teas contain different sets of polyphenols, as well as statin chemicals.
Chinese. Raw, un pressed puerh. Has not been secondarily fermented yet, though can be consumed as is but will not deliver the dark, earthy characteristics of puerh.
Chinese. This is basically raw, Mao Cha that has been pressed into cakes of various shapes. This has not been through the secondary fermentation yet, and thus is often bought, and stored for decades to be drunk later in life. It can however be drunk as is, but will resemble green tea more than it will the earthy, fermented puerh teas. This is a broad term to refer to all unfermented puerh cakes in pressed form.
Chinese. This is Sheng Cha that has undergone the secondary fermentation process. These categories are a broad term to descripe a variety of puerh types.