Why does pour-over coffee turn out astringent?

Astringency in pour-over coffee is a tactile sensation, a tightening or rough, puckered feeling on the tongue and throat, not a taste like sour, sweet or bitter. It shows up even when brewing parameters sit inside the planned extraction range, because the compounds behind it are released by specific conditions during the brew rather than by one obvious mistake.

The guide starts from the nature of astringency, identifies which brewing problems release astringent substances, and gives targeted adjustments so the cup stays smooth. Finding words to describe coffee is hard even for regular drinkers, but astringency is noticed at once, so the fixes focus on grind, water temperature, pour and timing. A separate note covers whether can you get drunk on coffee, a different concern.

When many people drink a cup of coffee, it is often difficult to describe its specific flavor, but if an obvious astringency appears, almost everyone can notice it immediately. Front Street's back office often receives reader questions: even though the brewing parameters are all within plan, why does the coffee taste tight in the throat and rough on the tongue? This article will start from the essence of astringency, sort out the sources of astringent substances in coffee, analyze the common brewing problems that cause astringency, and provide targeted adjustment plans to help you fundamentally avoid an uncomfortable cup of coffee.

For most people, it is often difficult to give a unified answer about what flavor a cup of coffee actually has, but if a clear astringency or astringent mouthfeel appears in a cup of coffee, then I believe everyone can quickly notice it upon the first sip.

On ordinary days, Front Street's back office often receives messages from readers, and quite a few of them ask how to avoid brewing astringency in coffee. For example, last week a friend said that during the entire brewing process nothing unusual was noticed, and the parameters were all within the extraction plan, but the coffee still had an uncomfortable feeling when drunk, and when swallowing, the throat and tongue had a sandy roughness that even lingered for a long time, so they guessed it was caused by too much astringency and wanted to know which step had gone wrong.

In Front Street's view, to solve the unpleasant "astringency" in coffee, we first need to understand this perception and find the pattern of its release, and only then can we fundamentally avoid this kind of problem.

What exactly does astringency feel like?

The so-called astringency is actually a kind of tightening sensation of being "seized" produced in the mouth and tongue, or a very rough, puckered feeling. In other words, astringency means not smooth, so it is a tactile sensation and does not belong to taste.

Although it is different from tastes such as sour, sweet, and bitter, as a tactile sensation that most people cannot accept, once we perceive the existence of "astringency," no matter how rich the aroma of the food is, the mind usually first recalls this negative impression. For example, when Front Street eats a banana that is not fully ripe, although the fruity aroma is also sensed, the rough feeling formed on the teeth after eating is always uncomfortable.

Where does the astringency in coffee come from?

In daily life, tea, red wine, and coffee all can have an astringent mouthfeel, but their sources are different. The astringency in tea comes from tea polyphenols, the astringency in red wine comes from the tannic acid in grape skins and grape seeds, and the astringency in our coffee comes from dicaffeoylquinic acid formed after the chlorogenic acid in green beans degrades during roasting, while substances such as tartaric acid and tannic acid are also sources of astringency.

If the coffee you drink has obvious sandy roughness, a mouth-drying feeling, throat-catching, dryness, and other astringency-leaning mouthfeel, then it is very likely caused by the above substances dissolving too much in the coffee or accounting for too large a proportion.

Strictly speaking, there are many reasons why coffee becomes astringent, including insufficient ripeness at fruit picking, a too-high defect rate in green beans, overly rough post-processing, improper transportation and storage, insufficient roasting development, and uneven extraction, all of which may be the "real culprits" causing astringency in coffee.

But as consumers, as long as you buy trustworthy brands, you basically will not encounter coffee astringency caused by green beans or roasting, because before these products are officially launched, they have already passed layer after layer of checks by growers in the place of origin, green bean traders, roasters, baristas, and other practitioners, so the quality is naturally reliable. Therefore, when you confirm that the product you bought has no problems, but the coffee you brew often has astringency, you might as well look for the reason in the following brewing details.

Which situations are most likely to cause astringency in coffee?

1. Brewing time is too long

I believe many people know that the release rates of various substances in coffee under the washing of hot water are different. Large-molecule substances dominated by bitterness and astringency usually dissolve intensively in the final stage. Therefore, when coffee has astringency, it is often accompanied by an unpleasant bitter aftertaste. From the logic of extraction, the longer coffee is brewed, the stronger the taste becomes, and the later it goes, the easier it is to release bitter and astringent flavors.

So if you want the coffee to be reasonably extracted, you must control the brewing time well. Taking a single serving of 15-16g coffee grounds as an example, Front Street recommends no more than 2 minutes and 30 seconds. When your actual brewing time exceeds two and a half minutes, and you do indeed taste bitterness and astringency, then to improve the coffee's taste, you must adjust the parameters according to the actual situation.

For example, if after brewing there is a large amount of wet muddy powder on the surface of the coffee bed, it means there are too many fines causing water retention, and the grind size needs to be coarser;

If most of the coffee grounds are concentrated at the bottom and look very flat, then it is most likely because the pouring force was too small, so the coffee bed did not rise, and the water could only be forced to seep down slowly through a thick obstructing layer, thereby prolonging the brewing time. The solution is to appropriately increase the flow of the water stream after blooming so that the water level rises as much as possible to two-thirds of the height of the dripper.

2. The washing force of the water stream is too strong

According to Front Street's observation, there are mainly two situations in which pouring problems cause astringency: the first is that an unstable water stream leads to uneven extraction of particles, making the coffee both sour and astringent; the other mostly comes from friends who are used to using a large water stream to stir the coffee bed, which easily washes out off-flavors and astringency in the later stage of extraction.

Unlike other parameters, pouring is a practical skill that requires constant practice. To achieve even brewing, Front Street recommends using a vertical water stream, keeping it 3-4 cm above the coffee bed, and then pouring slowly in circles.

3. The dripper's extraction efficiency is too high

For many beginners, the material of the dripper is one of the most easily overlooked causes of over-extraction. For example, ceramic drippers have the characteristic of a relatively high specific heat capacity. Preheating them in advance can provide good heat retention throughout the pouring process, but at the same time it also "quietly" improves the extraction efficiency of the coffee, thereby increasing the probability that astringency will be released in the final stage.

So when we drink coffee that has astringency, and the dripper used is made of ceramic, and the first two situations have already been ruled out, then we might as well start from temperature and try lowering the brewing water temperature by 2-3°C to reduce the risk of over-extraction.

The above content is compiled by CoffeeHunters, a coffee news website.