Measurement of (1 → 3),(1 → 4)-β-d-glucan

Abstract

Publisher Summary The major carbohydrate component of the endosperm cell walls of barley and oat grain is a mixed-linkage (1→3),(1→4)-β-D-glucan commonly termed barley β-glucan. Barley β-glucan forms highly viscous aqueous solutions and gelatinous suspensions. In the brewing industry it can lead to diminished rates of wort and beer filtration and to the formation of hazes, precipitates, and gels in stored beer. In an attempt to alleviate the problems caused by barley β-glucan in the brewing and animal feed industries, various approaches have been adopted including the breeding of barley varieties low in this component, the use of only well-modified malts in brewing, and the addition of enzymes active on barley β-glucan. None of these methods has been adopted as a standard procedure. Reasons for this include the lack of specificity or reliability of the assay or the tedious nature of the assay format that limits the number of samples that can be processed in a given time. This chapter describes an assay procedure that overcomes these limitations. In this assay, highly purified endo-1,3(4)-β-glucanase (lichenase) and β-glucosidase are employed. The glucan is depolymerized by lichenase to oligosaccharides, these oligosaccharides are quantitatively hydrolyzed by β-glucosidase to glucose, and this is specifically measured using glucose oxidase/peroxidase reagent. This method is suitable for the routine analysis of mixed-linkage β-glucan in cereal flours, malt, wort, and beer.