Brewers measure this by comparing the original specific gravity of the unfermented liquid against the final gravity after fermentation is complete. Apparent attenuation measures the simple drop in gravity using a hydrometer, while real attenuation accounts for the lower density of the newly created alcohol. Most standard ale yeasts achieve between sixty-five and eighty percent conversion.
Check the gravity on tank four, we're looking for at least seventy-five percent apparent attenuation before we crash it.
A sudden drop in typical attenuation for a specific yeast strain usually indicates poor yeast health, inadequate oxygenation before pitching, or a lack of yeast nutrients.
Related terms
Attenuate
To consume dissolved sugars during fermentation and convert them into alcohol and carbon dioxide.
Attenuative
Describing a yeast strain's inherent capability to ferment a high proportion of available sugars.
Wort
The sweet, unfermented liquid extracted from mashed grains that serves as the basis for beer or whisky.