Fermentation Levels in Ripe Pu'er: Light, Heavy, and the Microbes in the Pile
They're all called ripe (shou) pu'er, yet some brew a bright red liquor with a lively sweetness, while others are dark brown, nearly black, and as thick and smooth as rice porridge. Much of that difference comes from the "fermentation level" during wet piling (wodui). Tea factories decide when to take the tea out of the pile based on the raw material and the style they want.
What Happens in the Pile
Wet piling means sprinkling sun-dried maocha with water and heaping it up so that microbes become active in the hot, humid environment. Researchers have measured an actual wet-piling run: the whole fermentation took about 30 days, with the pile temperature held at around 50–63°C most of the time and dropping back to around 45°C near the end. Meanwhile:
- Tea polyphenols dropped sharply, by more than half in that measurement;
- Theabrownins rose markedly; these are one of the main sources of ripe pu'er's deep red liquor and mellow mouthfeel;
- Theaflavins and thearubigins changed as well, and the liquor shifted from yellow-green all the way to reddish-brown.
A team at Yunnan Agricultural University also tracked the entire ripe pu'er process and reached a similar conclusion: tea polyphenols declined steadily while theabrownins rose steadily, the two changing almost as mirror images.
Who's at Work in the Pile
Ripe pu'er isn't tea that has "gone off"; it's the result of a group of microbes working together, each with its own role. The main players researchers have found in the wet pile include Aspergillus niger, Bacillus, a yeast called Blastobotrys adeninivorans, and some heat-tolerant fungi. Aspergillus niger dominates the early stage of fermentation, while Bacillus and yeast take over later. One purpose of turning the pile is to adjust temperature and oxygen so these microbes do the right work at the right time.
How Tea Factories Control It
Parameters differ from factory to factory, but the industry's common general approach is:
- Sprinkling water: Depending on the maocha's moisture, add water equal to roughly 30–40% of the maocha's weight so the leaves absorb it evenly.
- Piling and insulation: Heap the tea to a certain height and cover it with damp cloth if needed so the pile temperature rises.
- Temperature control: Keep the pile at roughly 50–65°C; when it gets too hot, turn the pile to release heat so the leaves don't burn.
- Turning: The first turn is on the second day after piling, then about once a week, for 5–8 turns in total.
- Duration: The whole wet-piling period commonly runs 30–45 days, and some methods go longer.
These are ranges from experience; the real judgment comes from the tea master looking at color, smelling, and feeling the temperature.
Light Fermentation and Heavy Fermentation
"Light fermentation" and "heavy fermentation" are tea-world terms with no unified numerical definition. They are roughly understood like this:
| Light fermentation | Heavy fermentation | |
|---|---|---|
| Liquor color | Bright red, more translucent | Deep reddish-brown, dense |
| Aroma | Some of the leaf's own fresh sweetness, lighter ripe aroma | Pronounced aged, jujube, and woody aromas |
| Mouthfeel | Livelier, with a little astringency | Smooth, thick, sweet |
| Spent leaves | Reddish-brown with a hint of chestnut, springy | Dark brown, soft |
| Storage | Still has room to change | Very stable once made |
If fermentation goes further and overshoots, the spent leaves turn black, hard, and crumble when pinched; tea lovers call this "carbonized." The liquor may be dark, but it tastes hollow and thin, with no sweet smoothness.
After the Pile
Once fermentation reaches the ideal level, the pile is spread out and furrowed for ventilation so the leaves dry slowly; then they are sieved by size into different grades and picked clean of debris. Grades rich in fine, tender buds are often made into high-grade loose-leaf tea; coarser leaves have a thicker flavor and noticeable sweetness, and each has its uses. The little nuggets that stuck together during wet piling are picked out separately; these are the well-known lao cha tou.
How to Judge from a Cup of Tea
- Look at the liquor color: Poured into a white porcelain cup, bright red and translucent leans light fermentation; dark brown and opaque leans heavy.
- Smell it hot: If you can still smell the leaf's fresh sweetness within the ripe aroma, fermentation is lighter; full aged and jujube aromas mean heavier fermentation.
- Look at the spent leaves: Press with a finger; springy is good. Black, hard, crumbly leaves mean over-fermentation.
For the basic steps of making ripe pu'er and dealing with "pile flavor," read Wet Piling: How Ripe Pu'er Is Made.
Grades of Loose-Leaf Ripe Pu'er
Under the national standard, loose-leaf ripe pu'er is graded as special grade and grades 1 through 10, 11 grades in all. The higher the grade, the more buds and the finer and more tender the material; the lower the grade, the coarser the leaves. Tender grades have a silky liquor, coarse grades a thicker flavor with noticeable sweetness, and each has its fans. So-called "palace pu'er" (gongting) generally refers to high-grade loose-leaf ripe pu'er with many buds; it's a marketing term, not a grade name in the standard.
Fermentation Level and Brewing
| Fermentation level | Water temperature | Pouring rhythm |
|---|---|---|
| Light | 95–100°C | About 10 seconds for the first few infusions, to keep astringency in check |
| Medium | 100°C | 10–15 seconds for the first few infusions |
| Heavy | 100°C | Can be extended a little for a thicker liquor |
New Ripe Tea and Stored Ripe Tea
Ripe tea fresh from the factory often has a pile flavor. Kept in a clean, well-ventilated place for a year or two, the pile flavor fades and the liquor becomes cleaner and smoother. Lightly fermented ripe tea still has some room to change in storage, while heavily fermented ripe tea is relatively stable.
The Color Language of Ripe Pu'er
The liquor color of ripe pu'er is often used to judge fermentation level, but it's only accurate in a white porcelain cup under natural light: bright red and translucent leans light, deep red with brown is medium, and dark brown nearly black leans heavy. Yellowish indoor lighting makes the liquor look darker, so when comparing, use the same lamp and the same kind of cup.
FAQ
Is light fermentation better than heavy? There's no absolute answer. People who like liveliness and want to keep the tea to watch it change often choose light fermentation; those who like smooth, thick tea that's ready to drink once made often choose heavy fermentation.
Is darker liquor better for ripe pu'er? Not necessarily. Dark liquor may mean heavy fermentation, or it may mean over-fermentation. What matters is that the liquor is bright, not cloudy, and tastes sweet, smooth, and full-bodied.
Where does the aged aroma of ripe pu'er come from? Research has found a group of methoxybenzene compounds in ripe pu'er's aroma, produced as microbes transform the leaf's components during wet piling, giving ripe pu'er its distinctive aged aroma.