Pu'er or pu-erh is a variety of fermented tea traditionally produced in Yunnan Province, China. In the context of traditional Chinese tea production terminology, fermentation refers to microbial fermentation, and is typically applied after the tea leaves have been sufficiently dried and rolled. As the tea undergoes controlled microbial fermentation, it also continues to oxidize, which is also controlled, until the desired flavors are reached. This process produces tea known as hēichá (黑茶), literally "black tea", though the term is commonly translated to English as "dark tea" to distinguish it from the English-language black tea.
Pu'er tea
Shú pu'er tea, shúchá, brewed from a brick
Relatively young raw pu'er; note the grey and dark green tones
A pu'er tea factory, which steams, bags, and presses the loose leaf pu'er into tea bricks
Fermentation in food processing
In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—under anaerobic (oxygen-free) conditions. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.
Grapes being trodden to extract the juice and made into wine in storage jars. Tomb of Nakht, 18th dynasty, Thebes, Ancient Egypt.
Sourdough starter.
Conical loaves of bread left as grave goods, exactly as laid out in the Great Tomb at Gebelein, Egypt, 2435-2305 BC
Beer and bread, two major uses of fermentation in food