Degree of FermentationJune 19, 2012 # 6:07 PM # Brewing Analyses # 2 Comments
The degree of fermentation is the conversion of fermentable extract of wort during fermentation or the amount of extract removed in percentage of the original extract in the wort. The carbohydrates present in wort, e.g. glucose, fructose, maltose and maltotriose will normally be fermented and trace amounys of many sugars, higher carbohydrates e.g. dextrin and mineral salts remain unfermented.
The fermentable extract is determined by measuring of specific gravity of the wort and beer. This can be measured by saccharometer or pycnometer, hydro meter but commonly used commercial beer analyzer e.g. Scaba or Anton Paar for complete analysis.
Dependent on the method of determination the fermentation degree can be expressed as either Apparent Degree of Fermentation (ADF) or Real Degree of Fermentation (RDF).
Real degree of fermentation (RDF)
RDF is an expression for the fraction of extract
originally present in wort, which has been transformed into alcohol and CO2. It is calculated from the variables Alcohol (A) and Real Extract (ER) as determined by the beer analysis as follows:
%RDF = (2.0665A * 100)/(2.0665A+ER)
When the real extract content (ER) is
%ER = – 460.234 + 662.649 x SGER – 202.414 x SG2ER
Apparent degree of fermentation (ADF)
ADF is in principle equivalent to RDF only calculated using the apparent extract
(EA) instead of the real extract as follows:
%ADF = (2.0665A * 100) / (2.0665A + EA)
When the apparent extract (EA) is
%EA = – 460.234 + 662.649 x SGEA – 202.414 x SG2EA
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Also you can be estimated from using below formula:
RDF = 0.81 x ADF