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 (M-w) of protein components in wort, fermenting wort, beer and beer foam were analysed by high-performance size-exclusion chromatography. It was found that the M-w of protein during brewing was mainly distributed between 100 and 0kDa. From mash to the final beer, the most abundant protein component was the 7.6-2.1kDa 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 7.6-2.1kDa fractions increased significantly. In addition, the 100.0-13.2kDa fraction was the predominant thermolabile protein that decreased during lautering and boiling. The dominant protein constituting the fine coagulum, the 100.0-13.2kDa fraction, also decreased during fermentation and maturation. The CWB, defoamed CWB and CWB foam had similar protein M-w distributions, while the CWB foam concentrated much more protein and the 7.6-2.1kDa fraction was the major protein in the CWB foam. Copyright (C) 2015 The Institute of Brewing & Distilling