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.
Fluorometric determination of high-molecular weight β-glucan
wort, beer
The fluorochrome Calcofluor forms a complex with high molecular weight β-glucans (molecular weight greater than 10,000 Da). Complex formation results in an increase in fluorescence; however, this fluorescence is extremely unstable due to photochemical degradation. Through measurement in an automatic analysis system based on flow injection (flow-injection analysis), reproducible measurements for fluorescence and determination of β-glucan are possible. The device is calibrated using standard solutions of purified β-glucan from barley.