Pu-erh Catechins: Raw and Ripe Are Different Teas

Pu-erh catechins depend entirely on which pu-erh you mean. Raw pu-erh, sheng, keeps 100 to 150 mg per gram when young, close to green tea, and loses them slowly over decades of aging. Ripe pu-erh, shou, keeps very few, perhaps 20 to 40 mg per gram, because the wodu pile fermentation that defines it converts most of them into theabrownins. The two are made from the same leaf and are chemically further apart than green tea is from oolong.

That is the single most important fact about the category, and it is the one most often lost when pu-erh is discussed as a single thing. A buyer comparing a young sheng and a 2010 shou is comparing two different beverages.

The two processes

Sheng is the older method. Sun-dried green tea, called maocha, is steamed, pressed into cakes, and then aged. Nothing microbial happens at production; the transformation comes later, slowly, from the residual enzymes and from the ambient environment over years or decades.

Shou is the modern method, developed at the Kunming tea factory and standardized in 1973. Maocha is piled, watered and fermented for 30 to 60 days at 45 to 65 Celsius, in a process deliberately modeled on dark tea. It is an accelerated version of what sheng does over twenty years, and it produces a dark, smooth, earthy tea in months.

The numbers

The caffeine is the constant. The leaf is the same, and caffeine survives both aging and fermentation, so a cup of young sheng and a cup of shou carry similar caffeine at 30 to 50 mg.

Gallic acid is the marker of transformation. It rises in both routes, which is why an aged sheng moves toward the taste of a shou without becoming one. A twenty-year sheng is smoother and darker than a young one and still not earthy in the shou sense.

Why aging sheng is not the same as making shou

The difference is the organisms. Shou fermentation is driven by a hot, wet, microbial community over weeks, which produces theabrownins and geosmin in large amounts. Sheng aging is a slow, cool, largely chemical process at ambient humidity, which oxidizes and polymerizes without the same microbial signature.

The practical consequence is that old sheng does not taste like shou, and a drinker who dislikes one may like the other. The market sometimes blurs this, because aged sheng is expensive and shou is cheap, and describing a shou as old-style is a way to borrow the prestige.

• Sheng and shou are different products, not grades of one.
• Sheng keeps most catechins when young, shou keeps few.
• Theabrownins are the shou marker, at 40 to 80 mg per gram.
• Caffeine is unchanged in both routes.
• Old sheng is smoother but not earthy like shou.
• Aging sheng is slow chemistry, making shou is fast microbiology.

Brewing the two differently

Young sheng is brewed at 95 to 100 Celsius in a gaiwan, five grams per 120 ml, with short steeps. It is bitter and strong, and the bitterness is the point for its drinkers. Boiling it or steeping it long produces something harsh.

Shou is brewed at 100 Celsius or simmered. It is forgiving, and a rinse is essential because the pile leaves dust and the first pour is muddy. Three to five grams per 150 ml, longer steeps, and it keeps going for many infusions.

Aged sheng is somewhere between. It needs boiling water to open the compressed cake, and its bitterness has faded, so it tolerates longer steeps than a young one. A twenty-year cake is often brewed like a shou and drunk like a sheng.

The honest summary

Pu-erh is not one tea with one chemistry. It is two products, made from one leaf by two processes that diverge more than any other pair in the six classes. The catechin question cannot be answered for the category, only for the product.

The health claims that follow are equally split. Most of the research is on shou, because it is standardized and cheap to produce. Sheng has almost none, and old sheng is too expensive to study.

The aging curve of sheng deserves a specific figure. A young sheng at 100 to 150 mg of catechins per gram loses perhaps a third over ten years and half over twenty, depending on storage. That is slow enough that a five-year-old cake is still close to a green tea in its chemistry.

Storage conditions move that curve. A dry, cool, ventilated storage slows the change, and a humid one accelerates it. That is why two cakes from the same production can taste different after a decade, and why the vintage on a wrapper tells you less than the storage history.

Shou has no such curve. It is what it is after the pile, and further aging changes it little because the microbial work is done. A 2010 shou and a 2020 shou from the same producer taste similar, which is not true of sheng.

The consequence for a buyer is that the aging story belongs to sheng. Paying a premium for an old shou is paying for storage that did little, and the market knows this even when the marketing does not.

• Sheng and shou are two products, not two grades.
• Young sheng keeps 100 to 150 mg of catechins per gram.
• Shou keeps 20 to 40 mg per gram.
• Theabrownins are the shou marker, at 40 to 80 mg per gram.
• Caffeine is the same in both, 30 to 40 mg per gram.
• Old sheng is smoother but never earthy like shou.

A reader who remembers one thing should remember that the pu-erh category figure is meaningless. The two halves differ more than most tea categories differ from each other, and any statement about pu-erh that does not say which half is a statement about a category that does not exist chemically.

That also explains why the health claims are split. Shou is what gets studied, because it is standardized and cheap. Sheng is what gets romanticized, because it is old and expensive. The two stories are told about the same word and they describe different beverages.

The practical consequence for a buyer is to know which one is in the tin. A cake labeled pu-erh with no other information is ambiguous, and the price and the producer are the only clues.

The 1973 date is worth expanding because it marks a genuine discontinuity in the category. Before it, all pu-erh was sheng, and the aged cakes that the market now prices astronomically were simply tea that had been left for a long time. The ripe process was developed to produce something like that taste in months rather than decades.

The imitation succeeded at the level of appearance and general character and failed at the level of detail. A good shou is dark, smooth and earthy. An old sheng is dark, smooth and layered, with a sweetness and a returning aftertaste that shou does not reproduce.

That is why the two live side by side in the market rather than one replacing the other. Shou is the everyday tea and sheng is the collector’s tea, and the chemistry explains why the roles are distinct.

The grade of leaf matters less in pu-erh than the process, but it is not irrelevant. Old-tree material is picked from trees rather than bushes, and its leaves are larger and thicker, which slows extraction and gives more infusions. The chemistry per gram is broadly similar.

That is worth saying because the market prices old-tree cakes at multiples that suggest a chemical difference. What the material buys is texture, durability and a story. Those are real qualities in the cup and they are not catechin content.

A buyer deciding between a young plantation sheng and a young old-tree sheng is buying a difference in taste and longevity of the session rather than a difference in health-relevant compounds.

One number worth carrying away is the ratio between the halves. A young sheng has roughly four times the catechins of a shou from the same region, and the gap widens with age because the sheng keeps losing them slowly while the shou has already lost most.

That single comparison explains why the health claims are unevenly distributed and why a drinker who wants catechins should not buy shou. It also explains why shou is the smoother drink: the compounds that make tea bitter are the ones that are gone.

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