Preparation, Structural Characterization and Antibacterial Property of Dialdehyde Carboxyl Corn Starch

In this study, high amylose corn starch (HA) was oxidized with double oxidation system involving TEMPO-NaBr-NaClO and NaIO₄ to prepare double aldehyde carboxylated starch (DACA). Molecular exclusion chromatography, multi-angle laser light scattering, Fourier infrared spectroscopy, X-ray diffractometry, scanning electron micrographs and thermogravimetric analyzer were utilized to analyze the molecular weight, particle size, multi-scale structures and thermal property of the oxidized HA. Also, the antibacterial property of DACA prepared from different amounts of NaIO₄ against Gram-positive (negative) bacteria was investigated. The results showed that oxidized HA presented increased water solubility, decreased molecular weight and particle size. Meanwhile, with oxidization, the intensity of C-O-C bond absorption bands in the range of 990~1159 cm⁻¹ was weakened, and the crystalline structure was destroyed into amorphous state, and the granular structure was also changed into lamellar and pore structures. Furthermore, the initial (T_o) and peak (T_p) temperatures of the thermal cleavage were both reduced, which was decreased more with increasing addition of NaIO₄. The residue of oxidized HA in thermal cleavage was 37%~40% of the original mass, which indicated that the thermal stability of oxidized HA was decreased, while presenting difficult decomposition in high temperature region. With the increase content of aldehyde group, the oxidized HA showed enhanced inhibitory effect on the proliferation of S. aureus and E. coli bacteria. The above research results can provide ideas for expanding the application of corn starch and oxidized starch in food industry.