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.
Colorimetric determination of high molecular weight β-glucan
wort, beer
The colorimetric method may be used for the determination of high molecular weight β-glucan in wort; it is based on the photometric evaluation of a β-glucan color complex. The soluble β-glucan from barley reacts with a buffered solution, forming a color complex within 30 minutes. The absorbance of this β-glucan color complex is measured at 550 nm.