Fractionation of Starch by Selective Precipitation with Butanol

Abstract

By means of selective precipitation with butanol, a method of starch fractionation has been developed which avoids retrogradation and hydrolytic degradation. The precipitated fraction (constituting 22% of either corn or potato starch) is isolated in unique spherocrystalline form, prob-ably as an addition compound with the butanol. The butanol precipitated fractions from corn and potato starches are more alkali labile than the respective raw starches, while the non-precipitated fractions are correspondingly more alkali stable, indicative of definite chemical differences. The butanol precipitated fraction from corn starch tends to revert to insoluble form and appears to be the component of the starch responsible for gelation and retrogradation. The non-precipitated fraction from corn starch constitutes the more soluble and stable component. With potato starch, the physical differences between the fractions are less pronounced, since the butanol precipitated portion is more soluble and less subject to retrogradation than the conesponding fraction from corn starch. The phosphorus in potato starch is principally associated with the non-precipitated fraction. Waxy maize starch is peculiar in possessing an unusually low alkali lability and in giving no precipitate with butanol.