In 2015, people in the market often said that this year's tea was more astringent than in previous years. So, what exactly in the tea soup makes us feel this astringency?

What is astringency? A quick search on Baidu will tell you that astringency is a sensation that makes the tongue feel rough and uncomfortable. If you're not quite sure what that feels like, try eating a raw persimmon—astringency is exactly that kind of non-smooth sensation.

Why does drinking tea produce this sensation? The收敛 (convergent) astringent 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 rather by stimulating tactile nerve endings through interaction with proteins.

The main components in tea leaves that cause收敛感 (convergent sensation) and produce astringency are primarily tea polyphenols. Tea polyphenols, also known as "tea tannins," are a class of polyphenolic mixtures found in tea plants. They can be divided into catechins (flavanols), flavonoids, flavonols; anthocyanins, leucoanthocyanidins; phenolic acids and缩酚酸类 (depside-like compounds), collectively called flavonoid substances.

Tea Polyphenol Extract

In previous studies, Robichoud et al. found that most polyphenolic substances with astringency also have bitterness, and both bitter and astringent intensities increase with concentration.

When drinking tea, bitterness and astringency are generally inseparable; where there is bitterness, there is often astringency, it just depends on which is more prominent. Generally, caffeine is the main cause of bitterness in tea. The alkaloids in the tea soup form hydrogen-bonded complexes with a large amount of catechin substances. In teas where the relative content of both catechins and caffeine is relatively high, the tea soup tastes rich, mellow, fresh, and refreshing.

Catechins and caffeine have a synergistic effect on taste receptors but also restrain each other, reducing bitterness and coarse astringency. Therefore, tea with rich internal components does not necessarily exhibit strong bitterness and astringency.

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

Physical Reasons: The same tea can be perceived differently by different people; the same tea can be perceived differently by the same person depending on their physical state. Empirically, when a person has excessive internal heat (上火, huǒqì), the perception of astringency in tea tends to be more pronounced.

Weather for Tasting

Different weather conditions can lead to different tasting experiences. Generally, on clear autumn days when one is calm and peaceful, the tea soup's taste is perceived as more balanced and full-bodied; during hot and humid weather, it's easier to perceive astringency.

Brewing Method: The way tea is brewed affects its presentation. The stewing method can make bitterness and astringency more noticeable, which is also a common brewing method used in sensory evaluation.

Raw Material Ecological Environment: Problems in the ecological environment around the tea garden can lead to increased astringency in the tea leaves, such as pollution in the surrounding environment (e.g., rubber plantations), excessive fertilization, or herbicide use.

Single vegetation and direct sunlight lead to higher tea polyphenol content, resulting in strongly bitter and astringent tea.

Kill-green (杀青, shāqīng - enzyme deactivation) should be done to an appropriate degree, adjusting to the tea. Low kill-green temperature (under-kill-green) or high kill-green temperature (over-kill-green) are both detrimental to improving tea quality and will increase astringency.

Heavy rolling, which causes high cell breakage rate, and prolonged pile-up after rolling, will increase the tea's astringency.

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

After Pu-erh tea成品 (finished product) is pressed into cakes, it needs to be appropriately dried in a baking room. Note here that the baking room temperature should be below 60 degrees Celsius. Otherwise, short-term high temperature in the baking room can kill the enzymes still alive inside the tea, making the bitterness and astringency unable to mellow (不化, bù huà) and losing the potential for later transformation.

If the storage environment is too humid, and the tea's water content exceeds 13%, the tea's astringency increases.