Chá gāo, chá duōfēn (TP), chá huángsù (TF)

In Chinese tea culture and the modern tea industry, “tea extracts” refers to several different things: the historical concentrate paste chá gāo (茶膏), as well as isolated biochemical fractions of the leaf — polyphenols (TP, chá duōfēn 茶多酚) and theaflavins (TF, chá huángsù 茶黄素). They share one common trait: this is not the leaf itself, but its condensed or purified essence.

What is 茶膏 (chá gāo)

茶膏 — literally “tea paste” or “tea cream” — is a solid or semi-solid concentrate obtained by evaporating tea infusion down to a thick mass, which then solidifies into cakes, cubes, or granules. In form, it is a relative of instant tea, but traditionally it is an artisanal product, not a powdered one. A small piece of chá gāo dissolves in hot water, yielding an instant infusion without leaves.

The best-known variety is pu-erh paste — pǔ’ěr chá gāo (普洱茶膏), made from Yunnan raw material. Historically, however, the paste was also made from other types of tea.

History: From the Tang to the Qing Imperial Court

Concentrating tea is one of the oldest technologies in Chinese tea drinking. As early as the Tang dynasty, pressed and boiled-down forms of tea existed, and during the Song period, condensed tea products are mentioned among tributes. It is generally believed that the very principle of gāo — boiling down an infusion to a paste — took shape during this era (precise dating of early forms is debatable, so caution is warranted here).

The flourishing of chá gāo is associated with the Qing court. A persistent tradition holds that in palace workshops (the so-called “court” technology gōngtíng 宫廷), pu-erh paste was prepared for imperial consumption by repeatedly infusing and slowly evaporating raw material at low temperature. This product was valued as a convenient, transportable, and long-keeping concentrate. Specific recipe details of court production are documented only fragmentarily, and much of what is called the “court method” today is a reconstruction rather than direct inheritance.

How chá gāo Is Made

Technologically, there are two fundamentally different schools.

Traditional boiling down (decoction). Finished tea (most often shu or sheng pu-erh, or black tea) is repeatedly infused, the infusions are combined, and simmered for a long time over low heat or in a bain-marie. The result is a dark, resinous mass, which is shaped and dried. This method is gentle on aromatics but labor-intensive and yields a small output.

Modern industrial extraction. Leaves or finished tea are extracted with hot water, the infusion is filtered, concentrated under vacuum at reduced temperature (to preserve thermolabile compounds), and then dried — using spray-drying or vacuum-drying methods. This produces both chá gāo cakes and powdered instant tea. Low-temperature vacuum is the key to preserving aroma and reducing polyphenol losses.

The quality of the paste is determined by the raw material, the number of extraction cycles, the temperature regime, and purity (absence of scorching, foreign impurities, and minimal ash content).

TP — Tea Polyphenols (chá duōfēn 茶多酚)

TP (tea polyphenols) is a collective name for the group of phenolic compounds in the tea leaf, which account for a significant share of the dry matter in fresh raw material. The main subgroup consists of catechins (flavan-3-ols): EGCG, EGC, ECG, EC. It is the catechins that are responsible for the astringency, the “body” of the infusion, and its tart bitterness.

TP extract is obtained from tea leaves (often from green tea, as the richest in non-oxidized catechins) through aqueous or aqueous-alcoholic extraction, followed by purification and concentration. It is a raw material for the food and cosmetic industries, as well as an analytical benchmark for tea quality.

To determine the content of polyphenols and catechins in tea, standardized laboratory methods are employed. In the Chinese standardization system, this is covered by a national standard of the GB/T series, which describes spectrophotometric and chromatographic determination of total polyphenols and catechins (the exact standard number is intentionally omitted here to avoid error — one should verify against the current edition).

TF — Theaflavins (chá huángsù 茶黄素)

TF (theaflavins) are orange-yellow pigments that form during the fermentation (oxidation) of tea, primarily black tea (hóngchá 红茶). They arise when the enzyme polyphenol oxidase oxidizes and pairwise “stitches” catechins together: thus, colored benzotropolone structures are born from colorless flavan-3-ols.

Theaflavins are a quality marker for black tea:

• They give the infusion brightness and a golden sheen (that very “golden ring” around the edge of the cup);
• They are responsible for fresh astringency and liveliness (briskness) in the taste;
• They participate in the formation of “cream” — the clouding that appears as the infusion cools.

Upon further oxidation, theaflavins transform into larger and darker thearubigins (TR, chá hóngsù 茶红素), which provide a reddish-brown color and a rich “body.” The balance of TF and TR is one of the key evaluation parameters for black tea: a high theaflavin content with a sufficient level of thearubigins is considered a mark of high grade.

Purified theaflavin preparations are isolated from black tea using chromatographic methods; this is an expensive and technically complex product.

Taste and Brewing

茶膏. The paste is used extremely economically: a small piece (literally pea-sized) is enough for a cup or a small teapot. It dissolves in hot water within seconds. Pu-erh chá gāo yields a deep, dark-wine-colored, almost black infusion with a smooth, oily texture, earthy and woody tones in shu versions, and a brighter sour note in sheng versions. Due to the high concentration, dosage is crucial: an overdose makes the drink astringent and flat. Water is used hot (around 90–100 °C), with taste adjusted by the amount of paste rather than steeping time.

TP and TF in their pure form are not a ceremonial beverage, but rather ingredients and analytical standards. Within leaf tea, it is precisely their ratio that determines the perceived profile: high TP — pronounced astringency and bitterness; high TF — brightness and invigorating freshness; high TR — depth and soft fullness.

How to Distinguish and What to Look For

When buying chá gāo, rely on several signs:

• Surface and fracture. High-quality paste has a smooth, glossy surface without cracks or bubbles; the fracture shows a homogeneous glassy or resinous structure without inclusions or scorched particles.
• Solubility. A good concentrate dissolves fully and quickly, leaving no haze from insoluble sediment or a film of unburnt raw material.
• Infusion purity. The brew should be transparent (for its color), without “stewed,” burnt, or chemical notes, and without excessive bitterness.
• Origin of raw material. For pu-erh paste, a clear indication of type (shu/sheng), region, and year is important; vague descriptions are a reason to be wary.

Signs of a dubious product: a sharp burnt smell (overheating during evaporation), an artificial glossy “caramel” note, astringent chemical harshness, poor solubility with an oily film.

When evaluating leaf tea based on TP and TF content, one should rely not on marketing figures on the packaging, but on laboratory reports performed according to current GB/T methods: these fractions cannot be reliably measured with household means.

Summary

茶膏, TP, and TF are three faces of a single idea: to extract and concentrate the active part of the tea leaf. Chá gāo does this “as a whole,” preserving the entire palette in a convenient concentrate form with a long history stretching back to the imperial court. TP and TF, in contrast, break tea down into its components — into astringent catechins and bright fermentation pigments — giving the industry and science precise tools for understanding and controlling quality. Where specific standards, GB/T numbers, and court recipes remain disputed or undocumented, it is more reasonable to acknowledge uncertainty than to build history on guesswork.