Fermentation is Key to the Digestive Benefits of Pu erh Tea
In a previous post, some basic Chinese medicine theory about the nature of ripe pu erh explained the mechanism behind its digestive benefits. Central to this perspective is the metabolism-boosting effects of heat in pu erh and that weak digestion is due to waning heat production within the digestive system itself.
The fermentation process that ripe pu erh undergoes changes it from being cold in nature, like raw pu erh and green tea, to warm. It seems pretty fair to conclude that it is the enzymes and probiotics that are key to changing its constitution. This would be a mistake. There are plenty of cold probiotics, such as sauerkraut and yoghurt. However, the wodui (渥堆) method of processing hand-twisted broad-leaf variety Camellia sinesis subjects the tea leaves to a heat transformation as with any other type of composting. The micro-cultures, e.g., Aspergillis niger, specific to foods processed in a manner similar to pu erh may carry a heat factor that differs from the probiotics in foods like sauerkraut, e.g., Acidophilus. Who knows. It is likely that not all probiotics possess the the same properties. Even more compelling is that the convection involved with the wodui fermentation method plays at least as significant a role in changing pu erh’s character as any particular microbe.
pu erh tea masters bring their preferences to the crafting of a product. This not only includes the blend of leaf material, called mao cha (毛茶), but also involves the amount mao cha is fermented before being pressed into shape, as well as the density of the pressing itself. These differences lead to some ripe pu erh being relatively green and some relatively cooked. Usually, the older the product the more cooked it is, which is why old material is preferred over young. Often, a young production is crafted with the intention of letting it age for a few years. It is a good idea to keep these considerations in mind when buying ripe pu erh.
Pressed material comes in the form of bricks, birds nest, and what some have likened to “cow pies” but are otherwise called cakes, i.e., bing. As a rule of thumb, bricks undergo transformation slowest because they are packed tightest. “Transformation” is the degree to which the mao cha has oxidized first through wodui and second through storage. Both steps will increase the “earthiness” and reduce the astringency of the final product. “Astringency” is a trait often confused for bitter. They often go together but are not the same. Astringent is an effect on the mouth, the feeling associated with eating food like pecans or drinking a robust Irish breakfast tea. It is particularly absent from white tea or heavily fermented pu erh. Secondary storage, a factor to be discussed later, is greatly affected by humidity and heat and distinguished as being either wet- or dry-stored.
Many attribute the action of tea to antioxidants, like catechins. Though this may be true for green tea and raw pu erh, as a matter of fact fermentation converts catechins into theaflavins and thearubigins, constituents of black tea. Regular black tea, like Yunnan Gold, is generally not an aged tea nor is storage a factor as with pu erh. In a previous post, a distinction was drawn between what is called black tea in the East as opposed to everywhere else. Western black tea is not fermented and freshness is key. Chinese black tea, hei cha (黑茶), is fermented and age is prized. Oxidized teas without fermentation are called red tea, i.e., hong cha, (红茶). Microbes are a distinctive feature of hei cha, like ripe puer, aged-raw pu erh, and fu tea. Both teas, hong cha and hei cha, contain theaflavins and thearubigins but the difference lies in the “earthy” taste of pu erh compared to the floral and astringent qualities of hong cha.
In this passage, your humble pu erh Junky has sought to elaborate on some factors concerning the fermentation of ripe pu erh as it relates to the promotion of digestion. Microbial factors are central to the character of ripe pu erh tea, but the convectional heat arising from wodui process plays an equally important role. Though oxidation is a trait possessed by both hong cha and hei cha, only hei cha has microbes that are central to its taste and character. Fermentation occurs in two stages. The first stage is wodui and the second is storage. pu erh tea masters bring different skills to fermentation and in some instances cakes are meant to be stored for a few years before drinking. Thus, ripe pu erh possessing the greatest digestion-promoting attributes tend to be earthy with little astringency.
