behaviour
Attenuation
The proportion of wort sugars a yeast consumes — the single biggest determinant of how sweet or dry a finished beer tastes.
Apparent attenuation is calculated from original and final gravity and is what brewers normally quote. It reads slightly high because alcohol is less dense than water, so a hydrometer in finished beer under-reads; real attenuation corrects for that and is always lower.
Attenuation is not purely a property of the yeast. Mash temperature determines how fermentable the wort is in the first place, so the same strain can finish at very different gravities depending on how the wort was made.
Behaviour
| Apparent attenuation | 60–100% |
|---|
Questions
What is apparent attenuation?
The percentage drop from original gravity to final gravity, calculated as (OG − FG) ÷ (OG − 1). It is called "apparent" because alcohol is lighter than water, so a hydrometer reading of finished beer understates the true sugar removal. Real attenuation is typically about 80% of the apparent figure.