The production process of Anhua dark tea is complex, divided into the initial processing stage in spring and the refining stage in summer and autumn. The initial processing stage mainly includes steps such as picking, wilting, rolling, piling, re-rolling, and drying over an open fire in a seven-star stove using pine wood.
The picking season for Anhua dark tea is from around the Guyu (Grain Rain) solar term in mid-to-late April to around the Mangzhong (Grain in Ear) solar term in mid-to-late June. The raw materials for making Tianjian, Gongjian, and premium brick tea are relatively tender, mainly consisting of one bud and two or three leaves. The raw materials for making dark brick and Fuzhuan tea are relatively coarser, mainly consisting of one bud and four or five leaves, and sometimes even including tea stems that have started to turn red and have wrinkled leaves. Because the picked tea leaves are relatively coarse, a crescent-shaped tool called a "tea picker" is often used to cut the tea branches during picking; otherwise, it would be difficult to pluck them by hand.
Before wilting, dark tea was traditionally processed in iron woks. Because the raw materials are older and have a lower water content, water is often sprinkled on the surface of the tea leaves before wilting. Now, machine wilting is generally used, adjusting the temperature based on the tenderness and moisture content of the fresh leaves for simmering and timely stirring.
The rolling of dark tea is divided into initial rolling and re-rolling. Initial rolling is done while the tea leaves are still hot after wilting, allowing the tea leaves to be rolled into strips and the tea juice to be released, creating conditions for piling. Because the leaves are coarse, care must be taken during rolling to avoid separating the leaf flesh from the veins; otherwise, the leaf surface will curl up like a loofah, and the leaf stems will peel, resulting in substandard tea.
The rolled tea leaves do not need to be broken up before piling. The ideal conditions for piling are generally a room temperature of 25°C and a relative humidity of around 85%. Piling continues until the tea leaves turn yellowish-brown, the grassy smell disappears, and a sweet fermented aroma is emitted. Although the piling process of dark tea and the fermentation of black tea seem similar, they are actually different. The fermentation of black tea primarily involves the oxidation of substances such as polyphenols. After rolling, the tea leaves need to be loosened to allow contact with oxygen. Polyphenol oxidase from within the tea leaves promotes the oxidation and polymerization of monomeric catechins into oligomeric or polymeric tea polyphenols. The piling and fermentation of dark tea (Hei Cha) mainly involves microbial fermentation, along with some enzymatic oxidation reactions. Under the action of microorganisms, polyphenol oxidase, protease, cellulase, and pectinase are formed, which not only produce theaflavin-type polyphenols but also hydrolyze more edible fibers, tea polysaccharides, and peptides. The piling and fermentation of dark tea is similar to the fermentation in winemaking, both involving microorganisms, which is why it emits an aroma similar to sweet wine lees.
After piling and fermentation, the tea leaves become loose, so they need to be re-rolled appropriately to maintain the tightness of the tea strips, further refine the shape, and break down cells, thereby enhancing the extraction of internal substances during brewing and improving the appearance.
Next is drying. Traditional Anhua dark tea uses a seven-star stove with pine wood and open flames for drying. This specially constructed stove has seven holes and burns pine wood, without avoiding open flames or smoke. The wet tea is added in 7-8 batches during drying. When the upper layer is about 80% dry, the tea leaves are turned over, switching the upper and lower layers, until the tea is completely dry. Note that the seven-star stove must use pine wood for burning, not other miscellaneous woods, otherwise the taste will be wrong. Also, the pine wood must be sufficiently dry, otherwise there will be too much smoke, and the drying will become smoking. Drying involves open flames and smoke is acceptable, while smoking only involves smoke without open flames.
Tea dried using the seven-star stove has a dark, oily luster and a unique pine smoke aroma. This is a unique drying method for Anhua dark tea. However, the seven-star stove also has its drawbacks: low yield, high cost, and slow speed. Furthermore, the construction of the seven-star stove, the type of pine wood used, and the method of burning all require specific techniques. Currently, only a small portion of tea is dried using the traditional process with pine wood and open flames in a seven-star stove. Most manufacturers use drying machines, drying the tea leaves for about 10 minutes each time, usually three times in total. This method is efficient, fast, and low-cost, resulting in a clearer tea liquor. However, some believe that drying machines only dry the leaves, and cannot dry the moisture in the tea stems as thoroughly as traditional seven-star stoves. Tea dried this way is prone to reabsorbing moisture and does not store well. Nevertheless, due to the high demand for Anhua dark tea in the market, drying machines remain the most common drying method.
In addition, a few tea factories use sun drying and charcoal roasting. The former is affected by weather conditions, while the latter combines the advantages of both the seven-star stove and the drying machine. Some believe that high-quality dark tea should not have a smoky flavor, but rather a roasted flavor, which better preserves the tea's natural floral aroma and prevents the tea's fragrance and taste from being affected by pine smoke. Charcoal roasting is the most expensive method and produces a smaller yield, and is generally only used to process high-end dark teas like Tianjian.
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