Changes in beer bitterness level during the beer production process

Beer has been enjoyed by consumers for years. Today, hops are inextricably associated with this beverage. Although they have been the subject of research for decades, knowledge of their bittering components and interactions during the beer production process is still incomplete. Current literature clearly indicates that the bitterness experienced in beer comes from a much wider range of compounds than just iso-alpha-acids. Although compounds that can be classified into beta-acids, humulinones, hulupones, hard resins, and polyphenols are characterized by lower levels of bitterness and are present in hops in lower quantities than alpha-acids, they might determine, together with them, the final level of bitterness in beer. Unlike alpha-acids, the influence of compounds from these groups, their transformations, changes in their content during the beer production process and factors that affect their final concentration in beer have not yet been thoroughly studied. In case of alpha-acids, it is known that factors, such as chemical composition of wort, its extract and pH, amount of hops added and alpha-acids' content, boiling time, and temperature at which hops were added influence the level of bitterness. This phenomenon is further complicated when dry hopping is used. Due to the presence of humulinones, polyphenols, and alpha-acids, a relatively simple spectrophotometric determination of IBU can give erroneous results. IBU determination, especially in dry-hopped beers, should be coupled with HPLC analysis, taking into account appropriate bitterness coefficients.

Automated summary

Beer bitterness comes from compounds other than iso-alpha-acids, and the influence and changes of these compounds have not been fully studied. HPLC analysis should be used in combination with spectrophotometric determination of International Bitterness Units (IBU).