Dark tea (also known as post-fermented tea) is a class of tea that has undergone microbial fermentation, from several months to many years. The exposure of the tea leaves to humidity and oxygen during the process also causes endo-oxidation (derived from the tea-leaf enzymes themselves) and exo-oxidation (which is microbially catalysed). The tea leaves and the liquor made from them become darker with oxidation. Thus, the various kinds of fermented teas produced across China are also referred to as dark tea, not be confused with black tea. The most famous fermented tea is Pu-erh, produced in Yunnan Province, and the Anhua black tea produced in Anhua County of Hunan Province.
Dark tea is unique because it is the only deliberately aged tea that undergoes a secondary fermentation process. Because of this additional step, it contains an active micro-organism called Golden Flowers (Eurotium Cristatum). This micro-organism is present specifically in Dark tea made in Anhua County, Hunan Province, China. Golden Flowers is actually visible in some Dark teas and looks like tiny yellow flecks.
Puer, which is a sub-category of Dark tea, contains a different micro-organism called Asper Nigellus. This is due to variation in growing conditions, soil, and geography. Golden Flowers is a relatively new discovery, having just been identified in the last 30 years. To this day, the process of making Dark tea is a closely guarded secret. Here are some quick facts about Anhua Dark tea for all you biochemistry buffs out there:
- Significant polyphenol content
- Significant L-Theanine content
- Significant thearubigin & theaflavin content
- Significant polysaccharide compounds
Dark tea is a critical source of minerals and nutrients to people in many areas of China.
Though it looks ugly, but it is definitely a try for tea lovers.