FINE STRUCTURE OF POTATO STARCH

S terling, C larence, and J ack P angborn. (U. California, Davis.) Fine structure of potato starch. Amer. Jour. Bot. 47(7) : 577–582. Illus. 1960.—Electron micrographs were made from replicas of fracture surfaces of Lintnerized potato starch. These showed that much of the starch substance is organized into radially arranged microfibrils of 220–320 A diameter and considerably greater length (at least over 4000 A). The microfibrils have parallel longitudinal ridges on their surfaces. These ridges are conceived to be outer projections of micellar strands' which are 80–90 A in diameter and occasionally at least up to 4000 A long. The diametral dimension was confirmed by X‐ray diffraction study of moist and dry, normal and Lintnerized potato starch. The X‐ray evidence also supported the electron micrographic interpretation that amorphous regions lie between the crystalline micelles. On the basis of X‐ray data, it was speculated that the molecules in a microfibril are all oriented alike.