Attenuation (brewing): Difference between revisions
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In brewing, '''attenuation''' |
In brewing, '''attenuation''' refers to the conversion of [[sugar]]s into [[ethanol|alcohol]] and [[carbon dioxide]] by the [[Ethanol fermentation|fermentation]] process; a more attenuated beer be [[dryness (taste)|drier]] and more alcoholic than a less attenuated beer made from the same [[wort]]. It is calculated by comparing the [[specific gravity]] of the extract before and after fermentation. Attenuation can range between two-thirds and four fifths, but is usually three quarters.<ref>Andrew Campbell, ''The Book of Beer'', 1956, p.53</ref> |
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| ⚫ | Because fermentation produces ethanol, which has a lower density than water (gravity of 0.787 at {{formatnum:25}}°C <ref name="Eng Tool" />), this will result in a higher value than the actual percentage of sugars consumed.<ref name="Palmer HTB" /> Brewers generally refer to this apparent attenuation when using the word without qualification,<ref name="BeerSmith" /> although the measurement of real attenuation—the actual percentage of sugar consumed by the yeast—is an important indicator of yeast health and for producing certain styles of beer. A beer which does not attenuate to the expected level in fermentation will have more residual sugar and thus be sweeter and heavier-bodied.<ref name="BYO" /> |
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:'''Attenuation = 100 % * (starting extract − current extract) / (starting extract)''' |
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Attenuation is calculated using a [[hydrometer]], which measures the specific gravity — the density of a solution, relative to pure water — by buoyancy. The higher the specific gravity of a solution, the higher the hydrometer floats. |
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This formula works with extract given in weight percentages or degree Plato. Extract refers to all the non water substances (sugars, dextrins, proteins, vitamins, minerals, etc.) that are present in the wort. The percent extract or [[Plato scale]] is a measure in percent of how much of the wort’s weight is extract. Since, at least in the wort and beer gravities that most brewers work with, an almost linear relationship between (specific gravity − 1) and extract percentages exists, the above formula can also be expressed as: |
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Apparent attenuation is calculated using the equation AA = (OG – FG)/OG, where AA is apparent attenuation and OG and FG are the original and final gravities. For example, if a beer’s OG is 1.050 and FG 1.010, then the apparent attenuation is (50 – 10)/50 = 80%. |
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:'''Attenuation = 100 % * (starting gravity − current gravity) / (starting gravity − 1)''' |
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for brewers who prefer to work with specific gravity.<ref name="Braukaiser" /> |
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==Real vs. apparent attenuation== |
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| ⚫ | Because fermentation produces ethanol, which has a lower density than water (gravity of 0.787 at {{formatnum:25}}°C <ref name="Eng Tool" />), |
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Measurement of this value is important in brewing because it is an indicator of yeast health and because specific attenuation levels are important for certain styles of beer. A beer which does not attenuate to the expected level in fermentation will have more residual sugar and will thus be sweeter and heavier-bodied than planned.<ref name="BYO" /> |
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==References== |
==References== |
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Revision as of 08:02, 29 May 2019
In brewing, attenuation refers to the conversion of sugars into alcohol and carbon dioxide by the fermentation process; a more attenuated beer be drier and more alcoholic than a less attenuated beer made from the same wort. It is calculated by comparing the specific gravity of the extract before and after fermentation. Attenuation can range between two-thirds and four fifths, but is usually three quarters.[1]
Because fermentation produces ethanol, which has a lower density than water (gravity of 0.787 at 25°C [2]), this will result in a higher value than the actual percentage of sugars consumed.[3] Brewers generally refer to this apparent attenuation when using the word without qualification,[4] although the measurement of real attenuation—the actual percentage of sugar consumed by the yeast—is an important indicator of yeast health and for producing certain styles of beer. A beer which does not attenuate to the expected level in fermentation will have more residual sugar and thus be sweeter and heavier-bodied.[5]
Attenuation is calculated using a hydrometer, which measures the specific gravity — the density of a solution, relative to pure water — by buoyancy. The higher the specific gravity of a solution, the higher the hydrometer floats.
Apparent attenuation is calculated using the equation AA = (OG – FG)/OG, where AA is apparent attenuation and OG and FG are the original and final gravities. For example, if a beer’s OG is 1.050 and FG 1.010, then the apparent attenuation is (50 – 10)/50 = 80%.
References
- ^ Andrew Campbell, The Book of Beer, 1956, p.53
- ^ "Specific Gravity - Liquids". The Engineering Toolbox. Retrieved July 15, 2014.
- ^ Palmer, John. "6.1 Yeast Terminology". How to Brew. Retrieved July 15, 2014.
- ^ "Apparent and Real Attenuation for Beer Brewers – Part 2". BeerSmith Homebrewing Blog. Retrieved July 15, 2014.
- ^ Palmer, John (July–August 2009). "Attenuation: Advanced Brewing". Brew Your Own. Retrieved July 15, 2014.
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