This glossary defines the words used in the world of beer. Click a word to see its definition. To narrow your search, you can also select a letter below.
5 words for the letter I
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I
I.B.U.
Stands for “International Bitterness Units.” This is the international system for measuring the bitterness of beer, used by all master brewers. It quantifies, in parts per million (milligrams per liter), the isomerized alpha acids responsible for bitterness.
Imperial Stout
Stout with a high alcohol content.
Infection
The appearance, while the beer is being made, of an abnormal fermentation, usually caused by bacteria. Beer can become infected at any stage of the process from wort boiling onward. Infection spoils the taste by giving off a sour flavor. People also speak of “wild beer” or of beer that has “turned.”
Infusion
Brewing process that consists of steadily raising the temperature of the brew to convert starch into sugars. A distinction is made between single-step infusion during mashing and multi-step infusion, carried out while starch is broken down into fermentable sugars.
IPA (India Pale Ale)
Very hoppy pale ale, born in England for export to India. Revived by American brewers, it now comes in many variants (West Coast IPA, New England IPA, Double IPA...) with intense hop aromas.