Fermented Tea and Aged Tea
Before drinking, many traditional teas are matured for months, years, or even decades. While green teas and lighter oolongs are best savoured when young, a variety of white, black, and oolong varieties can mature into new depths with age. Because processing processes may not completely eradicate the microscopic organisms naturally present in tea leaves, some teas undergo bacterial and fungal activity throughout age. Although these teas do not produce alcohol or lactic acids in the same way that beer or pickles do, they are fermented nonetheless, and certain vintages fetch tens of thousands of dollars per pound at auction.
Pu-erh is the most well-known of these fermented teas, and it's produced in China's Yunnan Province, as well as neighbouring Laos, Thailand, and Vietnam. This tea starts off as a green tea, but as it ages, the grassy flavours fade away, leaving a deep depth of varnished wood, worn leather, and mellow earthiness in its place.Liu an, my personal favorite, undergoes a similar process and is matured in little bamboo baskets lined with bamboo leaves that can be brewed alongside the tea. This is not to be confused with Burmese fermented tea leaves, which are lactofermented before being mixed into salads and are not used for tea.