The most important bitter substances in wort and beer are the iso-α-acids. In addition, β-acids and δ-acids can be identified as well, primarily in the wort. Furthermore, wort and beer contain other derivatives from the acids of the bitter substances found in hops, particularly products of oxidation, which can also contribute to the bitterness in beer.
Determination of iso α-acids and α-acids in beer, beer-based beverages and wort
This method is not suitable for beer, beer-based beverages or wort, which contain saccharin, p-hydroxybenzoic acid ester, salicylic acid or sorbic acid.
These bitter substances are extracted from the acidified sample using iso-octane. Certain disruptive substances are eliminated through washing the extract with acidified methanol. The concentration iso-α-acids as well as α-acids is determined by measuring the absorbance in alkaline methanol at 255 nm and 360 nm.