NON‐STARCHY POLYSACCHARIDES OF CEREAL GRAINS III. HIGHER MOLECULAR GUMS OF COMMON CEREALS

Using the principle of ammonium sulphate fractionation successfully applied earlier to prepare β-glucosan from barley, a similar product has now been obtained from oats, whilst a pentosan fraction free from hexosan has been obtained from rye; the nature of the araban-xylan association is discussed. In respect of water-soluble gum content and composition, mature grains of the five cereals rye, wheat, barley, oats and maize form a series, the characters of which are not unrelated to the taxonomic positions of these cereals. Rye is rich in water-soluble pentosan, but in wheat there is greater contamination of the abundant pentosan by glucosan, mainly apparently of dextrinous type. β-glucosan is the principal gum of both barley and oats, but the amount of pentosan in barley gum is considerably greater than in that from oats. Maize contains little water-soluble' material of gum-like nature and the principal water-soluble polysaccharide is dextrinous. All five cereals contain material, non-precipitable by ammonium sulphate, which yields glucose, xylose, arabinose and galactose on hydrolysis.