Tea Why is it astringent?

Why does drinking tea create this sensation? The astringent, puckering feeling when drinking tea is produced by the interaction of polyphenolic substances like tannins with salivary proteins and glycoproteins. Therefore, astringency is not generated by acting on taste buds but by stimulating tactile nerve endings through interaction with proteins.

The components in tea leaves that primarily cause the astringent sensation and produce astringency are tea polyphenols. Tea polyphenols, also known as "tea tannins," are a mixture of polyphenols present in tea plants. They can be categorized into catechins (flavanols), flavonoids, flavonols; anthocyanins, leucoanthocyanins; phenolic acids and condensed phenolic acids, collectively referred to as flavonoid substances.

Tea Polyphenol Extract

In previous research, Robichoud et al. found that most astringent polyphenolic substances also have a bitter taste, and both bitterness and astringency intensity increase with concentration.

When drinking tea, bitterness and astringency are generally inseparable; where there is bitterness, there is often astringency, depending on which is more prominent. Typically, caffeine is the main reason for the bitter taste in tea. In tea liquor, alkaloids form hydrogen-bonded complexes with large amounts of catechin substances. In teas with relatively high levels of both catechins and caffeine, the tea liquor tastes rich, mellow, fresh, and brisk.

Catechins and caffeine have synergistic effects on taste receptors but also constrain each other, reducing bitterness and coarse astringency. Therefore, tea rich in internal components does not necessarily exhibit strong bitterness or astringency.

So why does the tea in your hand show more pronounced astringency? It's due to the issue of synergistic balance among its internal components. Many factors in the environment and processing can disrupt this synergy, causing astringency to become prominent.

Physical Reasons

The same tea can be perceived differently by different people; the same tea can also be perceived differently by the same person depending on their physical state. Empirically, when a person has excessive internal heat or is in a state of 'fire,' they tend to perceive the astringency of tea more noticeably.

Weather for Tea Tasting

Different weather conditions can lead to different tasting experiences. Generally, on clear autumn days with a calm and peaceful mood, one tends to perceive the tea liquor as more balanced and full-bodied. During hot and humid weather, it's easier to perceive astringency.

Brewing Method

The brewing method can influence the presentation of a tea. Steeping methods, like prolonged infusion, can make bitterness and astringency more noticeable, which is also a common method used in sensory evaluation.

Raw Material Ecological Environment

Problems in the ecological environment around the tea garden can lead to astringency in the tea leaves. For example, pollution in the surrounding environment (like rubber plantations), excessive fertilization, or herbicide use.

Single vegetation and direct sunlight can lead to higher tea polyphenol content, resulting in strong bitterness and astringency in the tea.

Fixation (kill-green) should be moderate, tailored to the tea. Insufficient fixation at low temperatures or over-fixation at high temperatures are both detrimental to tea quality and can increase astringency.

Excessive rolling, leading to high cell breakage rate, and prolonged piling after rolling can increase the tea's astringency.

The traditional drying method for Pu-erh tea is direct sun-drying. If sunlight is insufficient on the day and the tea cannot dry completely, requiring two days, it can cause re-moistening, increasing the tea's astringency.

After Pu-erh tea is pressed into cakes, it needs appropriate drying in a baking room. It's important to note that the baking room temperature should be below 60°C. Otherwise, high temperatures for a short time can kill the remaining active enzymes in the tea, making the bitterness and astringency unresolved and losing the potential for later aging.

If the storage environment is too humid, with tea leaf moisture content above 13%, the tea's astringency increases.