Separation and determination of the amylose and amylopectin fractions of starch.

Most of the earlier procedures used for separating starch into amylose, the linear unbranched component, and amylopectin, the branched chain component (1, 2), have involved degradation and hydrolysis of the starch molecules, During the last few years, however, a number of methods have been proposed which fulfil, more or less, the necessary requirement of protecting the starch constituents from degradation. The more important of these methods for the separation of amylose from starch is based on its selective diffusibility in water at 60” or 80” (1,3), precipitability with butanol (4), thymol (5), or nitroparaffins (6), and adsorbability on cellulose (7). It is shown in this communication that these methods fail to effect clear-cut as well as quantitative separation of the two starch fractions, while the purity of the products obtained is also variable. It has been possible, by suitable combination of certain of these procedures, to preparelamylose and amylopectin, judged for their purity by the intensity of their iodine colorations under standard conditions, and to determine their exact percentages in any starch preparation by reference to a calibrated curve for intensity of iodine coloration with known mixtures of the pure fractions (3).