Astringency is a physical drying in the mouth rather than a taste. This covers how to tell it from bitterness, what causes it in coffee and how to brew it out. From Lance Hedrick's "Think Your Coffee Is Bitter? It Might Be Astringent (Here's the Fix)" (May 2026), which draws on a 2025 Ohio State study.
What it is
- Astringency is a physical drying, puckering or rough feeling. Certain compounds stop saliva lubricating the mouth, so surfaces rub with friction 0:53. A green banana, an under-ripe persimmon, a tannic red wine or 100% dark chocolate all do it unmistakably 1:10.
- It isn't bitterness. Bitterness is a taste, and astringency is a physical sensation. The two often come together, but they are different things, and the word gets used for anything that seems even slightly dry 1:32 1:55.
- Perception plays tricks. A hollow body or a very bitter cup can feel "dry" without your tongue actually drying, just as aromatics read as "sweet" with almost no sugar in the cup 3:56.
Where it comes from
- Coffee has no tannins, and hardly any polyphenols in the strict sense, so the tannin explanation used for wine and tea doesn't carry over (Lance Hedrick quotes the chemist Dr Samo Smrke) 6:24 6:39.
- A 2025 Ohio State study split coffee into compound groups and had trained tasters, calibrated on an astringent reference, find the driest fraction blind. Its carriers were melanoidins, the brown Maillard compounds every roast has 8:17 9:04 9:11.
- The drying seems to come from phenolic fragments of chlorogenic acid, broken down in roasting and taken up by a small-sized subset of those melanoidins 9:11.
- Fast, very light, borderline-underdeveloped roasts look worst. They make enough melanoidins and enough phenolic fragments, and darker roasting burns more of them out. A separate group of drying compounds appears only in dark roasts (a 2011 paper) 11:09 11:24 11:27.
- These compounds extract slowly, so the more you extract, the more astringent a cup can get 12:31 12:48.
How to fix it
- Check it's real. Taste one of the references above, then ask whether the coffee dries your mouth the same way 16:10. A cup that seems dry at low extraction is probably an imbalance, and a small tweak fixes it 12:55.
- Extract less. Coarser grind or a shorter ratio. With light and ultra-light roasts especially, don't push extraction far. If you're at 23 to 24% and can't shake it, come down 13:25 15:41. Lance Hedrick's own extractions have drifted lower for this reason, and he thinks the ceiling before astringency is lower than once believed (Scott Rao's "extract as high as you can before astringency" implies the same link) 13:37 14:08.
- Dark roasts. The dryness is more likely bitterness, so lower the water temperature, or the ratio 14:36 15:37 15:54.
- Thicker filter paper. Jonathan Gagné's idea that very fine particles (under about 5 µm) feel drying is unproven, but a thicker paper may help, and it also removes particles that muddy the cup 17:04 17:15.
- Some coffees just are more astringent than others 17:48.
See also Grind size and extraction and the astringency rows in Troubleshooting.
Summarised in our own words from the creators' videos, with every point linked to the moment it comes from. Notchbook isn't affiliated with or endorsed by any of these creators, so please watch the originals for full context. Sources
Keep reading
- Burr alignment
- Conical vs flat, and burr geometry
- Grind size and extraction
- Particle size distribution and fines
- Retention, static and RDT
- Seasoning new burrs
- Slow feeding and RPM
- Zero point and grinder scales
- Grinder workflow: single dosing, WDT, RDT, purging and storing beans
- Troubleshooting: what to change when a cup tastes wrong
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