Astringency

What it tastes and smells like

• drying, puckering grip
• stewed tea
• grape-skin harshness
• lingering roughness

Responsible compound: polyphenols and tannins.

Styles this tends to affect

Not where it belongs — where it is most likely to appear when something has gone wrong.

• American porter — A stronger, more assertive porter with deeper roast, firmer bitterness and often American hop character.
• American stout — A bold, hop-forward stout combining strong espresso roast with American citrus and pine hop character.
• Black IPA — An IPA with dark malt for colour and a light roast edge, keeping full citrus and pine hop character.
• Czech dark lager — A dark Bohemian lager richer and sweeter than its German counterparts, with caramel and light roast over a soft body.
• Dry stout — Sharp roasted-barley bitterness over a light body and a very dry finish — much lighter to drink than its colour suggests.
• English porter — The original dark British beer: chocolate and light coffee over a nutty malt base, restrained rather than aggressive.
• Foreign extra stout — A strong export stout, more intense in roast and body than a dry stout, historically brewed to travel.
• Grodziskie — A low-strength Polish wheat beer brewed entirely from oak-smoked malt: light, sharply hopped, very fizzy and unmistakably smoky.
• Imperial stout — The strongest stout: dense, viscous and intensely roasted, with dark fruit, chocolate and substantial alcohol warmth.
• Irish extra stout — A stronger, fuller dry stout with more malt depth and body while keeping the sharp roasted-barley character.
• Kentucky Common — A quick-turnaround dark American beer brewed largely from maize, often lightly soured, extinct since Prohibition.
• Munich Dunkel — Deep brown Bavarian lager led by rich Munich malt — bready and gently chocolatey, without real roast bitterness.
• Oatmeal stout — A stout brewed with oats for a silky, full mouthfeel, balancing roast against smoothness rather than sweetness.
• Schwarzbier — Nearly black but remarkably light on the palate: smooth roast, clean lager finish and none of the heaviness the colour suggests.
• Tropical stout — A strong, sweet, fruity stout brewed for tropical markets, with less roast bite than its Irish relatives.

If you are drinking it

A harsh, drying, over-stewed-tea character is a brewing fault. It is harmless but unpleasant, and it tends to build over a glass rather than fading.

Not a safety issue. Beer’s alcohol, hop compounds and low pH make it inhospitable to organisms that cause illness.

What causes it

If you are brewing it

• Brewer: Stop sparging when runnings fall below about 1.010, and hold sparge water at or below 76 °C. (prevents)
• Brewer: Adjust mash pH into the 5.2–5.5 range with acidulated malt or food-grade acid. (prevents)
• Brewer: Use dehusked roasted malt such as Carafa, which gives the same colour with far less tannin. (prevents)

Where in the process this comes from

Steps that can produce this fault when they go wrong. Each links to what the step is for and how it is controlled.

• Lautering — Separate sweet wort from spent grain, using the settled grain bed itself as the filter medium.
• Mash pH adjustment — Bring the mash into the narrow pH band where brewing enzymes work properly, using acid, salts or acidulated malt.
• Milling — Crack the malt kernel so water can reach its starch, while leaving the husks intact enough to form a filter bed during lautering.
• Sparging — Rinse the grain bed with hot water to recover the substantial quantity of sugar that would otherwise be left behind in the liquid clinging to it.
• Water treatment — Adjust the mineral content and alkalinity of brewing water so the mash reaches a workable pH and the finished beer has the intended balance.