Automated characterization of the bitterness unit of wort and beer using a flow injection analysis system

Bitterness is one of the most important factors in determining the taste of beer, and in the past was generally evaluated by the use of organic functions. Chemical measuring methods, however, have recently seen widespread use. The ASBC method is one such method. In this method, hydrochloric acid is added to 10 ml of beer in order to acidify it. Next, 20 ml of isooctane is added to the mix, after which isohumulones, a bitterness ingredient in beer, is extracted. Finally, the absorption of isooctane at a wavelength of 275 nm is measured. By multiplying this absorption rate by 50, one obtains the bitterness unit. The ASBC method shows good correlation with organic function tests, and therefore is widely used. An automated system that performs both the organic solvent extraction and the absorption measurement using the flow injection method has recently been developed. Bitterness units of beer and wort have been measured using this system. The time required to analyze one sample is approximately 5 minutes. The reproducibility of the measurement, in terms of the coefficient of variation, is 0.5% for beer and 0.7% for wort.