Glossary
Fermentation
Yeast converting the sugars in wort into roughly equal parts ethanol and carbon dioxide, along with the esters, phenols and other compounds that give beer much of its character.
Fermentation is not only an alcohol-producing step; it is a flavour-producing one. The same wort fermented with a Bavarian weizen strain, a clean American ale strain and a saison strain produces three beers that taste unrelated.
Temperature is the brewer’s main control over that character. Warmer fermentation produces more esters and fusel alcohols; cooler fermentation suppresses them, which is why lagers taste "clean" and expose malt and hop character rather than yeast character.
Related
- Ester — The fruity compounds it produces.
- Phenol — The spicy and clove-like compounds it can produce.
- Attenuation — How far it goes.
- Krausen — The foam that marks its most active phase.
More vocabulary
Arrested fermentation · Barrel ageing · Batch sparging · Biotransformation · Blending · Bottle conditioning · Bottom fermentation · Burtonisation · Cask conditioning · Centrifugation
See every term on the glossary index.
Last reviewed 2026-08-16.