A COMPARISON OF THE STARCHES FROM BARLEY AND MALTED BARLEY

Abstract

Starch has been isolated from barley and malted barley of the same sample of cereal. The malted‐barley starch had a higher apparent amylose content, a higher gelatinization temperature, and smaller granules than that from the original barley. Pre‐treatment of the granules of both starches with liquid ammonia was necessary to achieve complete dispersion prior to fractionation into their component amylose and amylopectin. The amylose from the malted‐barley starch was smaller in molecular size and had a higher β‐amylolys!s limit than that from the barley. The amylopectin fractions differed with regard to average chain length and β‐amylolysis limit, but they were of comparable molecular size. Calculation showed the two amylopectins to have similar internal chain‐lengths, but different external chain‐lengths, that for the malted‐barley amylopectin being smaller. This suggests that the malted‐barley amylopectin had been degraded by β‐amylase to a limited extent. Subfractions of amylose obtained on successive aqueous leaching of both granular starches showed a decrease in β‐amylolysis limit with increase in molecular size. The properties of the components from malted‐barley starch can be satisfactorily accounted for by assuming limited β‐amylolysis of the amylopectin and very limited α‐amylolysis of the amytose in the original barley starch. 1959 The Institute of Brewing & Distilling