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.