Microstructural and Morphological Characterization of Corn, Wheat, and Cassava Dialdehyde Starches at Different Oxidation Degrees

ABSTRACT The microscopic structure and surface morphology of dialdehyde starch (DAS) granules play a pivotal role in determining their functional and physicochemical properties. In this study, DAS samples derived from corn, wheat, and cassava with varying degrees of oxidation were prepared to investigate the effects of oxidation modification on the starch granule structure. Fourier‐transform infrared spectroscopy (FTIR), x‐ray diffraction (XRD), and differential scanning calorimetry (DSC) confirmed the successful introduction of aldehyde groups and the progressive disruption of crystalline regions within the starch granules. To further characterize morphological changes, light microscopy (LM), confocal laser scanning microscopy (CLSM), and atomic force microscopy (AFM) were employed. As the degree of oxidation increased, surface damage such as wrinkles, indentations, and fractures became more prominent. Moreover, starches from different botanical origins exhibited distinct degradation patterns: in corn and cassava starch, cracks initiated at the hilum and led to granule fragmentation, while the smooth and intact wheat starch showed more uniform peripheral defects that gradually propagated inward, resulting in complete structural disintegration. These findings provide a fundamental basis for elucidating the structure–property relationships of starch from the perspective of its crystalline structure.