COMPARISON OF BARLEY GUMS ISOLATED BY VARIOUS PROCEDURES

Abstract

A barley gum that is believed to be the undegraded, water-soluble, nonstarch polysaccharide of the grain has been isolated. Aqueous solutions of this gum are extremely viscous and are stable. Enzymes that degrade gum during simple aqueous extraction were inactivated first by refluxing barley grist in boiling 85% alcohol followed by extraction of the dried grist with a 1% solution of papain. Gums of lower degree of polymerization, as judged by viscosity measurements, were obtained by aqueous extraction and acid treatments. Two enzyme systems that degrade gums are thought to be present in barley. One (which is inactivated by alcohol) degrades the initially soluble gum and brings an initially insoluble form into solution. The second system (which is inactivated by papain) accompanies and degrades the initially soluble gum during aqueous extraction or in aqueous solutions of the preparation. The purest gum contains only 0.1% nitrogen, and this may be part of the molecular complex. Mild, cold, alkali treatment of this gum reduces molecular size considerably as measured by viscosity of solutions. "X"-enzyme isolated from a bacterial source cleaves the gum into two oligosaccharides of glucose and a component containing D-glucose, L-arabinose, D-xylose, and D-galactose. No free sugars are produced.