What is attenuation in fermentation?

• A. The percentage of fermentable sugars converted to alcohol and CO2 by yeast.
• B. The rate of fermentation
• C. The pH of the mash
• D. The color of the beer

Answer: (A)

Attenuation is the percentage of fermentable sugars that yeast converts into alcohol and carbon dioxide during fermentation. It shows how completely the wort is fermented and is typically expressed as apparent attenuation, calculated from original gravity (OG) and final gravity (FG) as [(OG − FG) / OG] × 100. Higher attenuation means more sugars were fermented, yielding a drier beer with higher ABV, while lower attenuation leaves more residual sugars for a fuller, sweeter body. Real attenuation is a more precise measure that accounts for non-fermentable components, but most homebrewing contexts use apparent attenuation. Attenuation is not the rate of fermentation, nor the mash pH, nor the color of the beer.