Structural Changes in Starch Molecules during the Malting of Barley

Abstract

Barley was made into a normal and an over-modified malt, and the loss in starch was 14.6 % and 67.7 %, respectively. Starch granules, isolated from the barley and malts, were observed by scanning electron and light microscopes. In normal malt, 14 % of the large granules were eroded and the small granules remained almost intact. In the case of over-modified malt, 38 % of the large granules were eroded, and a marked reduction was found in the population of the small granules. Iodine affinities and blue values of the starches increased as malting proceeded. The malting of barley resulted in an apparent increase in the amylose component of the starch but hardly affected its molecular size distribution when examined by Bio-Gel A-50m column chromatography. The fine structures of the barley and malt amylopectins were compared by Shephadex G-50 and Bio-Gel P-2 column chromatographies after debranching with pullulanase. No change was observed during malting in spite of a significant reduction in the amylopectin component of the starch.