Channels of maize and sorghum starch granules

The radial, tube-like channels of corn/maize and sorghum starch granules, which penetrate from the external surface inward toward a cavity at the hilum, were found to vary in depth of penetration from granule to granule. Most, but not all, channels spanned the entire granule matrix, from the outer surface to the central cavity. Under slight swelling conditions (water), cavities swelled somewhat closed, while channels appeared to remain open. Swelling also affected the permeability of the granule matrix to dye molecules. Penetration of an aqueous dye solution occurred primarily from the central cavity outward and laterally from channels. Even under the slight swelling conditions, colloidal gold particles filled channels and cavities, showing that they are voids.