Theaflavins, Thearubigins, and Theabrownin: Where Liquor Color Comes From

Pour a cup of freshly made raw pu'er and the liquor is yellow-green to golden; pour a cup of ripe pu'er and it's deep red with a touch of brown; pour a cup of raw tea aged twenty years and it falls somewhere between orange-red and chestnut red. Behind these three colors is the same group of molecules taking different paths under different conditions: theaflavins, thearubigins, and theabrownin.

All Three Pigments Come from Catechins

The most abundant phenolic compounds in tea leaves are catechins. Catechins themselves are almost colorless, but once oxidized, they join in pairs and keep polymerizing, the molecules growing ever larger and the color ever deeper:

Think of it as a road: catechins → theaflavins → thearubigins → theabrownin. The farther along the road, the more the liquor shifts toward reddish brown, with less freshness and more mellow fullness.

What Is Theabrownin?

Theabrownin isn't a single compound but the collective name for a large group of brown, water-soluble high-molecular polymers. Its backbone comes from oxidized polymers of catechins and other phenolics, often linked to polysaccharides, proteins, amino acids, and other constituents, so its molecular weight varies widely and it has no fixed chemical formula.

In the lab, theaflavins, thearubigins, and theabrownin are often measured by "systematic analysis": the tea is brewed, the three groups of pigments are separated by solubility using different organic solvents, and their absorbance is measured with a spectrophotometer. Theabrownin is characterized by being poorly soluble in solvents such as ethyl acetate and n-butanol but highly soluble in water, so it stays in the water layer.

Why Ripe Tea Has a Deep Red Liquor

The key is wodui. Ripe pu'er maocha spends more than 40 days in the hot, humid environment of the pile, where polyphenol oxidase remaining in the leaves, together with extracellular enzymes secreted onto the leaf surface by microbes such as Aspergillus niger, rapidly oxidize and polymerize the catechins. Heat and humidity speed up the reactions, covering in a few weeks the distance raw tea takes many years to travel. Theabrownin accumulates in large amounts, and the liquor becomes deep red.

Figures from research give a sense of scale (they vary widely by sample and method, so take them as ranges):

• A study tracking a 39-day wodui found that at unpiling, theabrownin was about 4.71%–6.21%, thearubigins about 0.62%–1.37%, and theaflavins at most around 0.1%.
• Another study comparing five teas made from Yunnan large-leaf tea found theabrownin at about 13% in ripe pu'er, about 3.5% in black tea, and about 1.5% in raw pu'er.

Whatever the figure, the shared trend is clear: ripe pu'er has very little theaflavin and the most theabrownin, so its liquor is red and deep, mellow on the palate, with little sharp astringency. The heavier the fermentation, the more pronounced this tendency. See Fermentation Levels in Ripe Pu'er.

How This Relates to Black Tea

Black tea and ripe pu'er both produce these three pigments, just in different proportions:

• Black tea relies on "fermentation" after rolling, which is really the leaf's own polyphenol oxidase catalyzing oxidation in a warm, humid environment. The main products are theaflavins and thearubigins, so black tea has a vivid, bright red liquor, and good black tea shows a golden ring at the rim of the cup.
• Ripe pu'er relies on wodui. Besides the leaf's remaining enzymes, there are large numbers of microbes plus heat and humidity, pushing the reactions all the way to theabrownin, so the liquor leans reddish brown, clear but not vivid.

That's also why ripe pu'er is usually classified in English as a post-fermented tea, a different category from black tea (a fully oxidized tea). For the difference between raw and ripe, read Raw vs. Ripe Pu'er.

How These Pigments Change with Aging

Raw tea: sun-dried maocha already undergoes a little oxidation during rolling and sun-drying, leaving some theaflavins and thearubigins. In storage, the water activity of dry tea is usually below 0.60, so enzymes and microbes are largely inactive, and the pigments move toward theabrownin bit by bit, mainly through very slow auto-oxidation and chemical bonding. That's why raw tea's liquor changes slowly year by year: golden for the first few years, orange-yellow to orange-red at around ten years, and reddish brown after longer. When ambient humidity is a little higher, drought-tolerant storage molds play a small part and change speeds up somewhat. The stages are described in How Raw Pu'er Ages.

Ripe tea: by unpiling, it's already dominated by theabrownin, and with further storage the liquor mostly stays reddish brown with little change. What storage brings is mainly a rounder aroma and mouthfeel; see Should Ripe Tea Be Aged?

Clues You Can See in the Cup

• Brightness: theaflavins and moderate thearubigins give the liquor a sheen; when theabrownin dominates and there are impurities, the liquor tends to look dull.
• Color at the rim: ripe pu'er in a white porcelain cup often shows a touch of orange-red at the rim; if it's black all the way through, it's often over-fermented or brewed too strong.
• Once it cools: strong liquor turns cloudy as it cools, as pigments bind with caffeine. This is cream down.

For how to read liquor color, see also Reading Liquor Color: From Yellow-Green to Deep Red.

FAQ

What is theabrownin? Theabrownin is a brown, water-soluble high-molecular substance formed when catechins and other phenolics oxidize and polymerize, often linked to polysaccharides and proteins. It's the main source of ripe pu'er's reddish-brown liquor.

Why does ripe tea have a deep red liquor? During wodui, heat and humidity, the leaf's enzymes, and microbes' extracellular enzymes act together to rapidly oxidize and polymerize catechins into thearubigins and theabrownin, giving ripe pu'er its deep red liquor.

Does raw tea's liquor turn red with long storage? Yes, but slowly. Raw tea relies on slow auto-oxidation, and its liquor moves from golden through orange-yellow and orange-red, approaching reddish brown only after ten-plus years.

Is pu'er's theabrownin the same as black tea's thearubigins? They're different stages on the same road. Black tea stops mainly at theaflavins and thearubigins, while ripe pu'er polymerizes all the way to mainly theabrownin, so their liquor color and mouthfeel differ.