Have you ever tasted a “sour” flavor while savoring tea? What kinds of sour flavors can be found in tea? Why does tea have a “sour” taste? Which types of sourness are good, and which ones are not? Let's explore these questions together!
Wuyi Sourness
Some high-quality Wuyi Rock Teas naturally develop “Wuyi Sourness” during their aging process.
In the mid-19th century, Western tea scholars discovered “tannin” (catechin) in rock tea and isolated “Wuyi Acid.” Later, it was confirmed that Wuyi Acid is a mixture of beneficial substances including gallic acid, oxalic acid, tannin, and quercetin. In 1847, Rolland isolated “Wuyi Acid” from Wuyi Rock Tea. In 1861, Hasewitz confirmed that Wuyi Acid is a mixture of gallic acid, oxalic acid, tannin, and quercetin.
It's important to distinguish between the genuine Wuyi Sourness, which is “sour but not cloying,” and the sour taste caused by processing errors, which can induce nausea. The latter might be referred to as “nauseating sourness.” Therefore, one should not blindly pursue the Wuyi Sourness. As the saying goes: “Though Wuyi Sourness is good, don't overindulge!”
Therefore: Authentic Wuyi Sourness is good, while nauseating sourness is undesirable!
Tieguanyin Sourness
The false sourness in Tieguanyin, known locally as “green sourness,” comes from insufficient fermentation time, such as when the tea leaves are picked and processed on the same day. Another type of sourness called “green king sourness” is produced through traditional methods and is truly derived from semi-fermentation.
When tea connoisseurs talk about Tieguanyin sourness, they refer to a subtle sourness accompanied by a slight astringency, reminiscent of the sensation after eating something sweet. This sourness is followed by a sweet aftertaste and a sense of hydration. There is also a feeling of astringency at the back of the tongue. This type of sourness is more common in the first three infusions of Tieguanyin with pronounced acidity, but such teas often exhibit a strong sweet aftertaste and full flavor!
Delayed sourness is formed through a new processing technique, which is itself undesirable, let alone the resulting sourness.
Therefore: Green sourness and green king sourness are good, while delayed sourness is undesirable!
Black Tea Sourness
In general, fermented tea will have some degree of sourness. However, if the tea soup tastes distinctly sour, it could indicate that the black tea was piled too densely or over-fermented during processing. Since black tea is fully fermented, excessive fermentation or poor timing can result in a sour taste after drying.
Additionally, black tea can develop a sour taste if it has been stored improperly for an extended period, becoming damp. The water temperature used for brewing can also affect the sourness, especially for delicate black teas. If the water is too hot, the sourness will be more pronounced. In theory, pronounced sourness in black tea is usually due to processing errors and is therefore undesirable!
Ripe Pu'er Sourness
For Pu'er, ripe Pu'er inherently possesses characteristics of sourness, sweetness, bitterness, astringency, aroma, smoothness, and its sourness can transform into sweetness, reaching the throat without being locked. The tea soup is smooth, and there should be minimal pile scent, which is more evident in aged ripe Pu'er. Some well-transformed ripe Pu'er may exhibit fruity sourness. (Desirable)
However, improper wet-piling can also result in a sour and rancid taste in ripe Pu'er. This negative sourness can feel untransformed and cause discomfort, such as a tightening sensation in the cheeks. This type of sourness is generally disliked. (Undesirable)
Where Does the Sourness Come From?
The sourness in tea can be divided into positive and negative types. The positive sourness can be considered a manifestation of the active components in tea. Negative sourness is often due to processing or storage failures.
Main Sources of Sourness:
1. Wild tea, due to the nature of the raw material, often has a sour taste.
2. Low-grade picking, with old stems included. Because the old stems are difficult to properly process, the finished tea is more likely to have a sour taste. Summer-picked teas can also exhibit sourness due to the increased moisture content during the rainy season.
3. During manual processing, if the tea is alternately shaken and covered for too long, or lightly processed and lightly rolled, the finished tea is more likely to have a sour taste.
4. If the tea is not dried in time during sun-drying, and the moisture content is too high, the finished tea is prone to developing a sour taste.
5. During fermentation, under the influence of heat and humidity or microorganisms, if the fermentation process is not properly controlled and the tea is not dried in time, the finished tea can develop a sour taste.
Points 2 to 5 reveal that the main cause is the involvement of moisture, leading to the formation of organic acids during anaerobic fermentation.
The presence of sourness in tea does not necessarily indicate poor quality, as it depends on the concentration in the tea soup and the balance between different components.
A good tea should have a balanced expression of “sour, sweet, bitter, astringent, fragrant, sweet, smooth, and heavy.”
Properly understanding the “sour” taste in tea and learning to distinguish between positive and negative sourness is essential knowledge for every tea lover.