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Two water-soluble polysaccharides have been isolated from barley, one (C2) yielding on hydrolysis glucose, xylose, and arabinose, the second (B2) substantially glucose only. Under the influence of barley enzymes a solution of C2, rapidly shows a fall in viscosity; prolonged action destroys its precipitability by Fehling's solution in presence of acetone. A polysaccharide of similar initial solubility relationships is, however, obtainable from malt; it has a considerably greater pentosan content and contains uronic anhydride, being closely analogous in composition to mixed barley hemicelluloses, the preparation of which is described. It is considered, therefore, that the malt product is a hemicellulose-dextrin mixture, produced from barley hemicelluloses by cytolysis. Since barley contains in insoluble form material similar to C2, it is not clear how far the viscosity reduction during cytolysis of C2 contributes to the viscosity fall in barley extracts during malting; solutions of the corresponding malt factor have moderate viscosity. Of the water-soluble polysaccharides, only B2 has substantial surface activity; however, this can be of no significance later in the brewing process, as there is no evidence that this material survives malting.
Preece et al. (Mon,) studied this question.