Observation of the Inner Structure of Corn Starch Granules by AFM

Abstract

In starch granule, although the molecular structures of amylose and amylopectin are almost becoming clear, their hierarchic structures in molecular level is stillunknown. Recently, a blocklet model that the starch granule consists of two kinds of blocklets with different size (∼500 nm and ∼50 nm) and crystallinity (hard and soft) was proposed, and the both sizes of blocklets have been observed by scanning electron microscopy (SEM). However, by atomic force microscopy (AFM), only the smaller size (∼50 nm) of blocklet has been detected. Thus, we developed a resin-embedded section method specific to starch granule observation. As a result, we successfully observed both the big blocklet and small blocklet were clearly observed in corn starch granules by AFM. Furthermore, we found a new structure with fibrous form (10∼12 nm in height) at a center of a granule, which might be a cluster structure of amylopectin molecule with a diameter of 10∼15 nm.