Thickness is a quality recognized by the general public and one of the common traits of good Tea.

Whether it's tea, liquor, or a bowl of slow-cooked soup, our recognition of thickness, like sweetness, comes from an unconscious drive that requires little training.

Thickness does not belong to our basic taste categories but is a tactile sensation.

A Cup of tea contains many substances, but not all contribute to its thickness.

If we simply consider the internal content, the water-soluble substance content should correspond to what is described as internal content.

However, in reality, the water-soluble substance content has little correlation with the thickness of the tea broth.

In other words, some teas may have high water-soluble substance content but still do not feel particularly thick.

This is not difficult to explain, mainly because there is not much correlation between thickness and the presence of polyphenols.

A simple, albeit not entirely rigorous, experiment can illustrate this more clearly.

Compare a concentrated infusion of Yiwu Pu'er tea picked in other seasons with a normally brewed Yiwu first spring Pu'er tea.

It turns out that even when the Yiwu Pu'er tea picked in other seasons is steeped concentrated, it cannot achieve the thickness of the Yiwu first spring Pu'er tea.

From the perspective of water-soluble substances, the concentrated Yiwu Pu'er tea should contain more, but when tasting, the broth feels both bitter and thin, lacking the full-bodied richness of the first Spring Tea.

Perhaps the polyphenols do not significantly contribute to the thickness of the broth, making it difficult for us to perceive the thickness.

So, what exactly influences the thickness?

The substances that create a sense of thickness are generally considered to be soluble sugars.

Soluble sugars not only include simple sugars and disaccharides (such as glucose and fructose) that we can distinctly taste, but also include soluble pectins, starches, and others.

These substances thicken the broth, creating a sticky tactile sensation.

In addition to soluble sugars, amino acids also play a supporting role, making the broth feel thicker.

The presence of soluble sugars and amino acids in a cup of tea is influenced by both the raw materials and post-processing factors.

Firstly, regarding raw materials, the thickness-producing substances in fresh leaves are primarily affected by season and tree age.

In general, during the spring, amino acid content is relatively higher, while soluble sugars are more abundant in the autumn.

The older the tree, the higher the relative content of soluble sugars and amino acids in the tea leaves.

Therefore, overall, the sensation of “thickness” in spring tea is more pronounced compared to tea from other seasons, and the older the tree, the fuller the flavor of the broth.

Different processing methods have varying effects on the thickness.

During withering and spreading, due to the action of hydrolases, the content of soluble sugars increases.

When scalding and withering occur under the influence of temperature and humidity, hydrolases accelerate their reactions, increasing the content of soluble sugars.

During kneading, tea juice overflows, and the tea strands form with the help of these highly viscous soluble pectins. Some of these pectins coat the exterior of the tea strands, influencing the thickness of the broth due to the increased leaching rate of these viscous substances.

The fermentation of black tea and the pile fermentation of dark tea produce large amounts of soluble sugars under normal processing conditions, enhancing the thickness of the broth. Therefore, under similar brewing conditions, black tea and Pu'er tea appear richer and smoother.

Thickness improves the overall sophistication of the tea's flavor.

This enhancement of sophistication may occur through three pathways.

First, substances that create thickness, such as soluble pectins, do not have much impact on taste, as they have no significant flavor.

What role do they play then?

I speculate that these sticky substances adhere to our taste buds, creating a certain degree of shielding effect.

Similar to using a neutral density filter in photography, which reduces the intensity of light, our perception of bitterness becomes more balanced.

In my own taste experiments, I had this feeling: when tasting pure polyphenols, the stimulation felt like a direct hit from a metal hammer.

After adding soluble Pectin, at the same concentration, it was like switching to a rubber hammer; the stimulation from the polyphenols became much milder.

Secondly, these highly viscous substances essentially act as lubricants, alleviating the rupture of the lubricating membrane caused by the combination of polyphenols and salivary proteins, reducing our sensation of astringency. In most cases, astringency does not come across as sophisticated.

Finally, these high-viscosity substances adhere to the walls of our mouth after swallowing the broth, along with a portion of sugars, low-concentration polyphenols, amino acids, and aroma compounds, enhancing the quality and duration of the aftertaste.