Structure of Starch Granules

Abstract

Starch granules are synthesized in a semicrystalline structure and have characteristic morphology and properties depending on the botanical origin and the organ of the plant. Surface gelatinization studies have shown that the internal structures of starch granules are not homogeneous and vary with radial locations, from the hilum to the periphery. The internal structure of maize starch granule coincides with the biosynthesis and development of starch granules and the expression of starch synthase activities during the maturation of maize kernels. The enzyme digestibility of starch granules relates to the internal structure and the internal surface area of the starch granule as revealed by confocal laser-scattering micrographs. Short branch-chains of amylopectin (DP 6–12) destabilize the granule structures, resulting in lobed or compound starch granules and small granules. Ratios of long branch-chains to short branch-chains of amylopectin molecules affect the shape of the molecule, e.g., cylindrical versus conical shapes. The shape of the amylopectin molecule may affect the packing of the molecules in the granule and, in turn, determines the morphology and the size of the starch granule.