Structural and chemical properties of native corn starch granules

Native corn starch granules were fractionated according to size and apparent density. Individual fractions were characterized by high performance size exclusion chromatography, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and enzymatic susceptibility. Native starch granules were not homogeneous; they showed differences in solubility, enzymatic susceptibility and crystallinity. The small, less dense granules were more crystalline than the more abundant larger and denser granules. Neither the degree of solubility of each starch fraction in methyl sulfoxide (DMSO), nor its enzymatic susceptibility, was correlated with fraction crystallinity. Starch granules with different sizes or apparent densities had inherent variations in their crystallinity, which influences granule functional properties. The helical nature of amylose and amylopectin may also contribute to the functional complexity and variability observed in the population of normal starch granules.