Enzymic degradation and nature of the endosperm cell walls of germinating sorghums and barley

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Abstract
β‐(1·3)(1·4)‐Glucans are the major components of isolated endosperm cell walls of both sorghum and barley grains and the concentration declines from 75% in unmalted barley walls to 32% in those of the 6‐day malts. In sorghums over the same period, the reduction was from 72 and 68% to 54 and 62% in varieties L187 and SK5912, respectively. Following germination wall pentosans, while enhanced in barley, decreased in sorghum. The enzymes which were unable to hydrolyse the walls of sorghum to release sugars (unlike those of barley) did so after the walls had been solubilised in alkali. Cellobiose accounted for 43% of the hydrolysates of the alkali‐solubilised walls when incubated with sorghum malt enzymes and 79% when barley enzymes were used. Laminaribiose was not detected in either case which indicates that the polysaccharide of the sorghum walls is largely of a ‘cellulosic’ nature. Preliminary evidence suggests that fuco‐xyloglucan may contribute to the resistance of the sorghum endosperm cell walls to enzymic attack during germination.