At the MBAA Regional in Philadelphia – At the MBAA Regional in Philadelphia – Oct, 2012 Oct, 2012 Gary Spedding, Ph.D. Gary Spedding, Ph.D. Managing Owner/Chemist & Sensory Managing Owner/Chemist & Sensory Specialist. Specialist. Brewing and Distilling Analytical Brewing and Distilling Analytical Services (BDAS) LLC. Services (BDAS) LLC.
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At the MBAA Regional in Philadelphia – Oct, 2012At the MBAA Regional in Philadelphia – Oct, 2012
Brewing and Distilling Analytical Services (BDAS) LLC.Brewing and Distilling Analytical Services (BDAS) LLC.
“Alcohol Measurement in Beer”
>Alcohol is generated relative to the amount of fermentable sugars in beer wort.>Is related to both wort specific gravity (SG) and wort RDF (Real or “true” degree of fermentation).>Accepted - 1 gram of alcohol requires 2.0665 g of fermentable extract.
[As originally determined: 2.0665 g sugar yields 1 g ethanol, 0.9565 g CO2 & 0.11 g yeast. Note: for equations below, 0.9565g & 0.11 g sum to 1.0665 extract NOT converted to alcohol.]
>Above values are used in varied published equations to determine alcohol strength.
Solving for alcohol determination by weight determinations (Karl Balling):
> [ABW: alcohol by weight (as w/w, grams of alcohol per 100 grams of beer). OG, original gravity & RE real or present extract.]
))100/0665.1(0665.2(
)(
OG
REOGABW
Brewers using a hydrometer - real extract can be approximated using OG and AE:
[(AE = apparent extract or attenuation – the value determined when alcohol is present) Note: this is only an empirical observation & applies only to traditionally fermented beers near 65 % RDF.]
Substituting into the above formula:
If the SG has been also been determined for the beer then the alcohol by volume can be determined with a correction to account for the specific gravity of the beer:
[Where, sp. gr: specific gravity, e.g., for the beer or pure ethanol.
Which simplifies to:
Variant equations are available but alcohol should be reported both % by weight (wt.) & by volume (vol.) to two decimal places. For reporting purposes brewers are allowed a tolerance of +/- 0.3% alcohol by volume.