Professional cellaring
Professional cellaring builds upon the concept of warehousing Tea to implement a more scientific and professional approach to “post-fermentation” (or post-aging). In the past, we considered “high temperature and high humidity” as critical factors for the post-fermentation of Pu'er tea, even designating areas that met these conditions as the best places for the tea's post-fermentation.
However, the post-fermentation process of Pu'er tea is not simply resolved by “high temperature and high humidity.” We may have overlooked an even more crucial factor: characteristic microorganisms. Characteristic microorganisms are those that significantly influence the quality of a fermented product. Without the presence or participation of these microorganisms, the inherent characteristics of the solid-state fermented product would be lost. For example, in the production of famous distilled spirits, countless microorganisms participate in the fermentation process, each contributing, to varying degrees, to the complexity of the spirit. However, some microorganisms are considered more important than others, and without them, the uniqueness of the spirit cannot be achieved. In the fermentation of strong-aroma liquor, ethyl hexanoate is one of the main acids, and the discovery of hexanoic acid bacteria in the cellar makes them characteristic microorganisms.
A good Pu'er tea cannot undergo its post-fermentation process without the intervention of characteristic microorganisms, and these microorganisms can only thrive, multiply, and accumulate within a specific environment, namely, a “cellar,” to achieve optimal fermentation rates.
The essence of professional cellaring is an attempt to apply a more scientific approach to the post-fermentation of Pu'er tea. It aligns with a nascent sub-discipline of tea chemistry called “tea storage chemistry,” which is a key area of research in this field.
There are five aspects worth our in-depth study, which I will also present as recommendations:
Firstly, professional cellaring for Pu'er tea is not merely the concept of a warehouse or storage center; it must first meet the hardware requirements of a “cellar.” This involves two aspects: the nature of the “cellar.”
A “cellar” is the place where post-fermentation occurs for Pu'er tea. Most cellars are enclosed spaces without windows or ventilation holes, creating a semi-anoxic environment that promotes the degradation, polymerization, and reduction of phenolic compounds in the tea, transforming large molecules into smaller ones. Even if intermittent ventilation is required, it must be done using specialized air purification equipment, which differs greatly from the ventilation fans and vents found in regular warehouses. Additionally, the walls and ceilings should be made of volcanic rock, stone with honeycomb pores, or treated “mud” to facilitate the “lodging” of microorganisms. The ceiling should be arched (since microorganisms prefer round shapes and avoid sharp angles).
Solid-state fermentation has much higher environmental requirements than liquid fermentation. This is because liquid fermentation involves filling liquids like wine or spirits into glass bottles or wooden barrels, which are relatively isolated from the air in the cellar. Therefore, the requirements for air quality, microbial flora, and personnel movement in the cellar are not very stringent. Post-fermentation of Pu'er tea, however, maintains a solid-state fermentation process, exposing the product to the air and allowing specific environmental microorganisms to “invade” and “occupy” it. Besides the need for enclosure, it is essential to separate human and material flow, requiring personnel to change clothes and disinfect themselves before entering the product area to prevent contamination and secondary infection (also known as secondary pollution). In this regard, a “tea cellar” is not a simple imitation of domestic or international wine cellars but requires more complex and rigorous facilities.
Secondly, a scientifically designed functional layout. The functional layout of a “cellar” should ideally consist of three sections: the service area (including reception, tea tasting, product display, and goods receipt and dispatch), the auxiliary area (including initial changing and disinfection, sensory evaluation room, chemical analysis room, microbial strain cultivation room, Pu'er tea characteristic microorganism sample room, water treatment room, and goods transfer area), and the core area (including secondary changing and disinfection, pedestrian passage, logistics passage, and several fermentation rooms). In the core area, different fermentation rooms control different temperatures and humidities through artificial intervention rather than relying on natural conditions. These three functional areas should form a ring-shaped structure, with the most critical aspect being the separation of human and material flows.
Thirdly, dedicated cultivation of characteristic microorganisms in the “cellar.” The microorganisms involved in the post-fermentation of Pu'er tea include bacteria, yeasts, actinomycetes, and molds. Among these, molds are aerobic microorganisms. During fermentation, as oxygen is consumed, the cellar becomes a semi-anoxic environment, leading to a decrease in mold numbers while yeast populations increase. When yeast populations decline, bacterial changes become particularly interesting.
This leads to alternating aerobic and anaerobic fermentation processes that repeat cyclically. During this process, we discover dominant microorganisms, and as the fermentation progresses, characteristic microorganisms emerge, performing the most critical work in the post-fermentation of Pu'er tea. Therefore, we can say that the cultivation and proliferation of characteristic microorganisms is the core technology of the “cellar” and its most valuable asset, ensuring the quality of the cellared tea. It also requires advanced biotechnology, such as monitoring water activity, balancing moisture content, managing moisture loss and heat removal techniques, and measuring the biomass of solid-state fermentation microorganisms. It is not simply a matter of controlling humidity and temperature, nor should it be a mere replication of “high temperature and high humidity.”
Fourthly, different types of Pu'er tea require distinct post-fermentation models. For example, raw and ripe teas, ancient tree teas, and plantation teas, along with their regional characteristics, necessitate specialized and standardized scientific approaches to cellaring. A “cellar” has spatial requirements, and in this specific space, Pu'er tea can easily undergo mixed fermentation with multiple microorganisms. As fermentation progresses, the ecological environment of the substrate (the Pu'er tea) changes, leading to a transformation in the microbial population according to certain patterns. Once these transformations can be quantified, the fermentation model can be established.
Once the fermentation model is established, the fermentation process can be artificially controlled, significantly shortening the fermentation time. Theoretically, professional cellaring can achieve a rate 20 times faster than simple warehousing. Of course, our research into the professionalism of cellaring aims not only to improve the efficiency of post-fermentation in Pu'er tea but also to enhance its quality.
Fifthly, there are two modes of professional cellaring. One mode is the “cellaring” model in the Pu'er tea-producing regions of Yunnan. The primary advantage of this model is that the characteristic microorganisms in the “cellar” are closely related to those in the surrounding tea gardens, benefiting from a unique geographical location. This is why famous distilleries, whether producing spirits or wine, locate their cellars near their production sites.
The French famous red wine-producing regions have long adhered to the concept of “château,” which essentially ensures a seamless connection throughout the production process to create the highest quality products. A “château” is not just a production facility but encompasses the entire process from harvesting to processing, brewing, and cellaring. This concept is now gaining attention in Pu'er tea-producing regions of Yunnan. The BLC Pu'er Tea Château was the first in China to establish a dedicated Pu'er tea cellaring facility, truly realizing the “seamless connection” from tea garden (tea cultivation) to tea factory (Tea processing) to tea cellar (professional storage). Its establishment not only completes the overall concept of the château but also fills the gap in Pu'er tea post-fermentation techniques through the development of various professional fermentation models, marking a significant technological innovation in the history of Pu'er tea.
The other mode of professional cellaring involves improving and elevating existing tea storage practices in Guangdong. There is potential for technical improvements and quality enhancements in this area. One can refer to the previous four recommendations and adapt them based on the natural environment of their storage facilities, attempting to cultivate advantageous characteristic microorganisms. Only then can professional cellaring be realized; otherwise, it remains at the level of simple warehousing.
Excerpt from “Pu'er” magazine
“The Temptation of Storing Tea”
If there are any copyright issues, please contact us for deletion.