BARLEY ENZYMES AND MALTING POTENTIAL

The amylases of barley are of only indirect significance in the modification of the starchy endosperm. More directly concerned are: ( a ) the β‐glucanase system (endo‐β‐glucanases, exo‐β‐glucanase, β‐oligosaccharases); ( b ) pentosanases (endoxylanase, exoxylanase, xylo‐oligosaccharases, arabinosidase); and ( c ) proteolytic enzymes, about which precise information is lacking. Contributions may also be made by phosphatases (including the complex system responsible for the hydrolysis of phytic acid) and Upases. The autolytic technique provides useful means for the study of these factors. Regarding the starch grains of the inner endosperm as being embedded in a matrix of β‐glucan, araboxylan and protein, the whole being divided into cell‐like units by walls of similar materials in high‐molecular state, modification may be taken to involve a balanced attack of hemicellulases and proteases on substrates in reasonably accessible physical state. Since the hemicellulases and probably also the proteases are apparently produced in superabundance, the physical state of the hemicelluloses and proteins appears to be most significant, and this same property may also play an important part in regulating water uptake by the grain and, in particular, its distribution among the various tissues.