Applicable for all (laboratory) worts
The Congress wort is heated in order to inactivate the amylolytic enzymes, and afterwards, yeast is added and the wort is allowed to completely ferment out at a minimum temperature of 20 °C in a fermentation tube (fig. 1). The difference in the extract before and after fermentation is measured in order to calculate the limit of attenuation.
The method is suitable for the determination of water vapor volatile aroma compounds in beer.
Volatile aroma compounds are driven out of the sample through steam distillation. The ethanolic distillate is saturated with NaCl. Potassium hydrogen sulfite is added to separate carbonyl groups that might interfere with the analysis. The extraction of the aroma compounds is performed by shaking out with dichloromethane and the phases separated by centrifuging.
Green beer, beer
The original gravity (p), apparent extract (EA) and real extract (ER) of the green beer and the fully matured beer are measured. From this, the apparent and real attenuation are calculated. Normally, only the apparent attenuation of beer is determined in practice.
The method is suitable for beers of all original gravities and of any alcohol content.
The gas chromatography headspace method is used to determine the higher alcohols and esters present in beer, i.e., the volatile compounds are transferred from the headspace in the sample vial into the GC system for analysis. The following substances are measured in this analysis:
Acetaldehyde
Propanol-1
Ethyl acetate
2-Methylpropanol
3-Methylbutanol
2-Methylbutanol
2-Methylpropylacetate
Butyric acid ethyl ester
3-Methylbutyl acetate
2-Methylbutyl acetate
Hexanoic acid ethyl ester
Applicable for all (laboratory) wort
The Congress wort is heated in order to inactivate the amylolytic enzymes, and afterwards added to an Erlenmeyer flask along with 7.5 g/100 ml yeast where it is allowed to completely ferment out under constant agitation. The difference in the extract before and after fermentation is measured in order to calculate the limit of attenuation.
Determination of the maximum amount of extract in the wort and beer
wort, beer
After adding yeast, wort or beer is fermented at a minimum of 20 °C in a fermentation tube. The limit of attenuation is calculated from the difference between the extract content prior to (original gravity) and after fermentation. [1]