β-Glucan is a polymer of glucose, which is joined together by roughly 30 % β-1,3- and 70 % β-1,4 glycosidic bonds. The majority of these polymers (approx. 75 %) are formed in the cell walls of the barley endosperm (the rest consists of proteins and pentosans). A partial depolymerization of the β-glucans takes place during malting through the action of β-glucanases. Further degradation during mashing is limited by the temperature sensitivity of the β-glucanases. For this reason, poorly modified malt may contain high molecular weight β-glucans (> 10,000 Da), potentially leading to difficulties during the processes of lautering and filtration.
β-Glucans themselves do not cause problems with filterability but rather β-glucans in the form of gel. This gel forms through exposure to shearing forces and higher temperatures over time.
wort, beer
β-Glucan gel has been shown to significantly lower the filterability of beer. The formation of a gel structure is primarily dependent on the concentration of β-glucan, temperature and time, as well as on the hydrodynamic forces causing shear and tensile stress, which occur during wort handling and beer production. The gel structure is thermo-reversible, meaning that a more desirable condition can be obtained through the application of heat.