Changes in protein molecular weight during cloudy wheat beer brewing

To investigate the changes in protein in cloudy wheat beer (CWB) brewing, the molecular weight (Mw) of protein components in wort, fermenting wort, beer and beer foam were analysed by high-performance size-exclusion chromatography. It was found that the Mw of protein during brewing was mainly distributed between 100 and 0 kDa. From mash to the final beer, the most abundant protein component was the 7.6–2.1 kDa fraction, which occupied more than 40% of the total protein. The extraction of soluble protein from malts into wort mainly focused on the protein rest process, where the 100.0–32.1 and 7.6–2.1 kDa fractions increased significantly. In addition, the 100.0–13.2 kDa fraction was the predominant thermolabile protein that decreased during lautering and boiling. The dominant protein constituting the fine coagulum, the 100.0–13.2 kDa fraction, also decreased during fermentation and maturation. The CWB, defoamed CWB and CWB foam had similar protein Mw distributions, while the CWB foam concentrated much more protein and the 7.6–2.1 kDa fraction was the major protein in the CWB foam.