ANALYTICAL EVALUATION OF α-ACIDS IN HOP EXTRACTS AND IN HOPS*

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Abstract
The results of new investigations on hop extract analysis are presented. The main findings are: 1 The specific extinction (257) of α-acids at 276 nm in iso-octane used at present in CCD and paper strip analyses is 3·5% too high: analytical results have therefore been too low. The new extinction value to be used is 248. 2 The result of paper strip analysis depends very much on the amount of α-acids placed on the strip. The three-point paper strip method can only partly correct this. In general, figures with paper strip analysis have a tendency to be too high. 3 Conductometric titration of α-acids produces a figure about 2 to 10% too low. This can be partly corrected by adding 20% dimethylsulphoxide or dimethylformamide to the titration medium. 4 Conductometric analysis of hop extracts with removal of “iso-α-acids like material” before titration is possible by a very simple procedure (pH 7 buffer extraction). New photometric and conductometric procedures based on these results give figures which are in agreement for something which must be practically true α-acids.