Introduction:Have you ever experienced a rough, dry, or astringent sensation on your tongue or in your throat when drinking pour over coffee? Although this “astringency” is not a taste, it can significantly affect the overall flavor profile. This article delves into the sources of coffee astringency, explores common extraction issues from the perspective of tactile sensations — including factors such as overly long brew time, improper water flow control, and overly efficient filter cones — and offers specific adjustment suggestions to help you refine your pour over technique and brew smoother, cleaner coffee.

When drinking coffee, if an obvious astringent sensation appears in the first sip, it often leaves a more lasting impression than acidity, sweetness, or bitterness. This feeling, akin to sandpaper scraping against the tongue and throat, is actually a negative mouthfeel that can greatly detract from the overall flavor experience. So why does pour over coffee sometimes turn out astringent? Is it due to poor bean quality or problems during the extraction process? This article will approach the issue from the perspective of tactile science, helping you understand the nature of coffee astringency and breaking down common extraction mistakes one by one, providing practical directions for improvement.

Many coffee enthusiasts, even when following standard brewing parameters, may still encounter coffee that feels rough or has an uncomfortable gritty friction on the palate. Some readers have reported that although all their brewing values appear normal, they experience a gritty, sand-like roughness on the tongue and in the throat that lingers, suspecting it's caused by excessive astringency. In fact, this discomfort is very likely the result of over-extraction or improper technique releasing astringent compounds.

The so-called “astringency” is not actually part of the traditional taste categories (such as sour, sweet, bitter, salty, or umami), but rather a tactile response. It manifests as a tightening, puckering, or frictional sensation on the oral mucosa and tongue surface, similar to the dry, rough feeling after eating unripe fruit. This sensation instinctively makes people feel the drink is “unclean” or “not smooth,” and even if the coffee itself has rich fruity or floral aromas, once astringency appears, the overall evaluation can easily take a hit.

In coffee, astringency mainly comes from compounds such as dicaffeoylquinic acid — produced when chlorogenic acids in green beans break down during roasting — along with other substances like tartaric acid and tannic acid. When these substances are released in excessive amounts during extraction, they can lead to the astringent taste we perceive. These compounds are typically released in the later stages of brewing, so if the brew time is too long, these undesirable substances are more likely to end up in your cup.

For the average consumer, if you're purchasing from a reputable brand or roaster, the likelihood of astringency being caused by green beans or roasting is relatively low. More often, the emergence of astringency is closely related to actual brewing techniques. If you’re using quality coffee beans but still frequently end up with astringent coffee, it’s advisable to examine and adjust for the following common extraction issues.

[1. Overly Long Brew Time] is one of the most common factors leading to astringency. During coffee extraction, different compounds are released at varying rates, and those related to bitterness and astringency — typically larger molecules — are often gradually released in the later stages of brewing. If the brew time exceeds the ideal range, these substances can be over-extracted, resulting in noticeable astringency and unpleasant bitter notes.

Generally, it is recommended that when using about 15–16 grams of coffee grounds for a single serving of pour over, the total brew time should be kept within 2 minutes and 30 seconds. If you find that your brew time exceeds this range and is accompanied by an unpleasant astringent sensation, you can adjust in the following two ways: if there is a lot of wet, sticky fine sediment left on the surface of the coffee bed, it may indicate that the grind size is too fine, causing restricted water flow and prolonged extraction time — in which case you should adjust to a coarser grind. Conversely, if the coffee grounds remain settled at the bottom with the coffee bed flat against the filter paper, it may be due to insufficient pouring pressure, preventing water from effectively penetrating the coffee bed. In this case, it is recommended to moderately increase the water flow speed after the bloom phase, raising the water level to about two-thirds of the filter cone height to promote even extraction.

[2. Excessive Water Flow Force] is also a common cause of astringency. Unstable pouring methods, such as inconsistent water flow — sometimes strong, sometimes weak — can lead to uneven extraction, over-extracting some areas while under-extracting others, resulting in a sour and astringent taste. Additionally, some brewers habitually use a strong flow to rapidly agitate the coffee bed. While this can speed up extraction, it may also release unwanted impurities and astringent compounds from the later stages of brewing.

The key to improving this issue lies in maintaining a “steady pour.” It is recommended to use a vertical water stream and maintain a distance of about 3–4 centimetersfrom the coffee bed, pouring in a slow, continuous circular motion. This helps achieve even extraction and avoids localized over-extraction. Practicing a stable pouring technique can effectively reduce astringency issues caused by improper water flow.

[3. Overly Efficient Filter Cone Extraction] is a detail that many beginners tend to overlook. The material and design of the filter cone — including heat conductivity and filter hole configuration — can influence the extraction rate. For example, ceramic filter cones, due to their high specific heat capacity, can maintain a stable brewing temperature but may also extend the extraction time, increasing the risk of releasing astringent compounds in the later stages.

If you are using a ceramic filter cone and have already ruled out other potential extraction issues, consider lowering the brewing water temperature by 2–3°C. This can help slow down the extraction rate, reduce the chances of over-extraction, and lead to a more balanced coffee flavor, thereby decreasing the likelihood of astringency.

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