The crystallization of starch.

Abstract

In the early stages of the malt diastase hydrolysis of starch, Lintner and Düll 1 obtained crystal clusters which gave the characteristic starch reaction with iodine, were insoluble in cold water but soluble in hot, and had a specific rotation of 196°. Beijerinck 2 dissolved starch paste by autoclaving and obtained microscopic needle clusters on cooling. These were biref ringent when viewed between crossed nicols, but did not show the black cross which is so characteristic of starch grains. The writers' associate, Van de Sande Bakhuyzen, 3 found that aqueous solutions of starch, prepared by the method of the writers 4 without the use of reagents or heat, give a precipitate with alcohol consisting of clusters of microscopic needles, which when viewed between crossed nicols are birefringent, without showing the black cross.

The writers repeated Beijerinck's experiments and verified his results. However, by autoclaving at a somewhat higher temperature, 150° to 160° C, and by the use of some other modifications of his method, they obtained clusters of larger needles, not merely from potato starch, but also from wheat, maize, canna and arrow-root starches. These crystals are but little soluble in cold water, more readily in hot. They give the iodine reaction.

Viewed between crossed nicols, the clusters are birefringent in all cases. In the case of wheat, maize, and arrow-root, the needles are very small. In the case of the potato and canna, they are relatively large—some of the clusters reaching a diameter over one-half that of the natural granules. The potato and canna clusters, moreover, show the black cross between crossed nicols about as plainly as the natural granules. In the canna clusters, the coni trast between the black cross and the white of the cluster is not so sharp as in the potato clusters.