Is it Normal for Coffee to Taste Astringent/Bitter? How to Solve Over-Extraction in Pour-Over Coffee?

For most people, it is hard to agree on what flavors a cup of coffee might have. But when it comes to noticeable astringency, nearly everyone detects it the moment they take the first sip.

FrontStreet Coffee's inbox frequently fills with messages from readers, many of them asking how to avoid brewing coffee with astringent flavors. Just last week, one reader mentioned that despite noticing nothing unusual during brewing and keeping every parameter within the extraction plan, the coffee still left an uncomfortable sensation: on swallowing, the throat and tongue felt a sand-like roughness that lingered for a long time. They suspected excessive astringency and wanted to know where it went wrong.

In FrontStreet Coffee's view, solving the uncomfortable "astringency" in coffee starts with understanding the sensation and identifying its release patterns. Only then can we fundamentally keep it from happening.

What Exactly Is Astringency?

Astringency is a "grabbing," constricting sensation produced in the mouth and on the tongue, or a very rough, wrinkling feeling. In other words, astringency means a lack of smoothness, so it is a tactile sensation rather than a taste.

Although it differs from flavors like sour, sweet, and bitter, as a tactile sensation most people cannot accept, once we perceive astringency, even if the food's aroma is rich, our minds tend to fix on that negative impression first. Think of eating an unripe banana: you perceive the fruit aroma, yet the roughness that forms on the dental membrane afterward remains uncomfortable.

Where Does Astringency in Coffee Come From?

In daily life, tea, red wine, and coffee all show astringent qualities, but their sources differ. The astringency in tea comes from tea polyphenols, while red wine's comes from tannic acid in grape skins and seeds. In coffee, astringency comes from dicaffeoylquinic acid - formed when chlorogenic acid in green beans degrades during roasting - along with substances such as tartaric acid and tannic acid.

If the coffee you drink has obvious sand-grain roughness, mouth obstruction, throat catching, dryness, or other astringent sensations, it is highly likely that these substances have dissolved excessively or make up too large a proportion of the cup.

Strictly speaking, coffee can develop astringency for many reasons: fruit picked before it is fully ripe, a high defect rate in the green beans, overly rough post-processing, improper transport and storage, insufficient development during roasting, and uneven extraction - all potential culprits behind an astringent cup.

As a consumer, though, as long as you buy from trustworthy brands you will basically never run into astringency caused by green beans or roasting. Those products pass through multiple layers of quality control by origin farmers, green bean suppliers, roasters, and baristas before they reach the shelf, so their quality is up to standard. When you have confirmed there is no problem with the product you bought but still frequently get astringency in the cup, it is worth looking at the brewing details below.

Which Situations Most Easily Lead to Astringency in Coffee?

1. Brewing Time Too Long

Many people know that various substances in coffee release at different rates under the scouring of hot water. The large-molecule substances that mainly contribute bitterness and astringency typically dissolve in concentrated form in the later stages. Astringency in coffee is therefore often accompanied by unpleasant bitter notes. In extraction terms, the longer the coffee brews, the stronger it gets, and the more likely those bitter and astringent tastes are to be released late in the process.

To achieve a proper extraction, then, you need to control the brewing time. Taking a single serving of 15-16g of grounds as an example, FrontStreet Coffee suggests not exceeding 2 minutes and 30 seconds. If your actual brewing time runs past two and a half minutes and you do taste bitterness and astringency, then to improve the flavor you have to adjust parameters according to what is actually happening.

For example, if a large amount of wet, muddy powder sits on the surface of the coffee bed after brewing, too many fine particles have caused water to pool, and you need to adjust to a coarser grind.

If the grounds are mostly concentrated at the bottom and look very flat, it is likely the pouring force was too small, so the bed never lifted properly and water could only seep slowly down through a thick barrier layer, prolonging the brewing time. The fix is to increase the flow rate appropriately after the bloom, trying to raise the water level to about 2/3 of the dripper's height.

2. Water Flow Scouring Force Too Strong

By FrontStreet Coffee's observation, pouring problems cause astringency in two main ways. The first is unstable flow leading to uneven particle extraction, which makes the coffee both sour and astringent. The second usually comes from people who habitually use a large flow to stir the coffee bed, which easily washes out miscellaneous flavors and astringency in the later extraction stages.

Unlike other parameters, pouring is a practical skill that takes constant practice. To brew evenly, FrontStreet Coffee suggests using a vertical water column, keeping it 3-4cm above the coffee bed, and pouring slowly in circular motions.

3. Filter Cup's Extraction Efficiency Too High

For many beginners, the material of the dripper is one of the most overlooked causes of over-extraction. Ceramic drippers, for example, have a high specific heat capacity. Preheating ensures good heat retention throughout the pour, but it also quietly raises the extraction efficiency, increasing the odds that astringency is released in the later stages.

So when you taste astringency, the dripper in use is ceramic, and you have already ruled out the first two situations, start with temperature: try reducing the brewing water temperature by 2-3°C to lower the risk of over-extraction.

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FrontStreet Coffee Recommendation

Astringency is often a matter of technique, but the bean sets the baseline. FrontStreet Ethiopia Yirgacheffe Gidding is a forgiving pour-over choice: a washed Yirgacheffe from a cooperative of about 300 farmers in the Worka area, showing clear citrus, berry, and floral notes with a green-tea-like finish. Its acidity is soft and bright rather than sharp, so it stays clean even when your timing runs a little long.

If you prefer a sweeter, fruit-forward cup, FrontStreet Ethiopia Huakui brings strawberry, passion fruit, and jackfruit aromatics with pronounced sweetness, very low bitterness, and a smooth, juicy body. Choosing a clean, well-sorted lot like this makes it much easier to tell whether an astringent note comes from the coffee itself or from the brew.