About Raw Pu'er
Over time, raw pu'er acquires an earthy flavor due to slow oxidation and other, possibly microbial processes. However, this oxidation is not analogous to the oxidation that results in green, oolong, or black tea, because the process is not catalyzed by the plant's own enzymes but rather by fungal, bacterial, or autooxidation influences. Pu'er flavors can change dramatically over the course of the aging process, resulting in a brew tasting strongly earthy but clean and smooth, reminiscent of the smell of rich garden soil or an autumn leaf pile, sometimes with roasted or sweet undertones. Because of its ability to age without losing "quality", well aged good pu'er gains value over time in the same way that aged roasted oolong does.
Raw pu'er can undergo "wet storage" (shīcāng) and "dry storage" (gāncāng), with teas that have undergone the latter ageing more slowly, but thought to show more complexity. Dry storage involves keeping the tea in "comfortable" temperature and humidity, thus allowing the tea to age slowly. Wet or "humid" storage refers to the storage of pu'er tea in humid environments, such as those found naturally in Hong Kong, Guangzhou and, to a lesser extent, Taiwan.
The practice of "Pen Shui" involves spraying the tea with water and allowing it dry off in a humid environment. This process speeds up oxidation and microbial conversion, which only loosely mimics the quality of natural dry storage aged pu'er. "Pen Shui" pu'er not only does not acquire the nuances of slow aging, it can also be hazardous to drink because of mold, yeast, and bacteria cultures.
Pu'er properly stored in different environments can develop different tastes at different rates due to environmental differences in ambient humidity, temperature, and odors. For instance, similar batches of pu'er stored in the different environments of Taiwan and Hong Kong are known to age very differently. Because the process of aging pu'er is lengthy, and teas may change owners several times, a batch of pu'er may undergo different aging conditions, even swapping wet and dry storage conditions, which can drastically alter its flavor. Raw pu'er can be ruined by storage at very high temperatures, or exposure to direct contact with sunlight, heavy air flow, liquid water, or unpleasant smells.
Although low to moderate air flow is important for producing a good-quality aged raw pu'er, it is generally agreed by most collectors and connoisseurs that raw pu'er tea cakes older than 30 years should not be further exposed to "open" air since it would result in the loss of flavors or degradation in mouthfeel. The tea should instead be preserved by wrapping or hermetically sealing it in plastic wrapping or ideally glass.
About the Pu'er tea
The Chinese tea history of Pu'er tea is fascinating. Pu'er tea is one of the oldest type of tea in China with a rich history of over 1700 years that can be traced back to the Eastern Han Dynasty (25-220 AD). During it's height of popularity Pu'r tea was freely traded and even used as money for the bartering of goods. Premium Pu'er tea was offered as a tribute tea to the Emperor of China and to this day Pu'er tea remains a highly valuable commodity. Pu-erh tea is revered in China as a traditional medicinal tea with many health benefits.
Unlike other teas that should ideally be consumed shortly after production, pu-erh can be drunk immediately or aged for many years; pu-erh teas are often now classified by year and region of production much like wine vintages.