Preparation and characterization of starch nanoparticles through ultrasonic-assisted oxidation methods

• The nanoparticles were produced by one time or twice oxidation and ultrasonication.
• The third sample was prepared by TEMPO-mediated oxidation with ultrasonication.
• The size of the nanoparticles reached 30–50 nm, 20–50 nm and 20–60 nm, respectively.
• The gelatinization temperature and enthalpy of the samples remarkably decreased.
• The nanoparticles had higher carboxyl and carbonyl content and lower crystallinity.

In this work, starch nanoparticles (SNPs) were prepared from waxy corn starch (WCS) through ultrasonic-assisted oxidation. Three SNPs samples were produced by one time oxidation followed by ultrasonic treatment (O1U1-SNPs), twice oxidation and twice ultrasonic treatment (O2U2-SNPs) and TEMPO-mediated oxidation with ultrasonic treatment (TEMPO-SNPs), respectively. Differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the thermal properties, morphology, and structure of the ensuing nanoparticles. The results revealed that the size of the O1U1-SNPs, O2U2-SNPs, and TEMPO-SNPs particles reached 30–50 nm, 20–50 nm and 20–60 nm, respectively. Compared to WCS, the crystallinity of the O1U1-SNPs, O2U2-SNPs and TEMPO-SNPs samples decreased from 36.32% to 11.35%, 1.64% and 1.72%, respectively. The O1U1-SNPs, O2U2-SNPs and TEMPO-SNPs exhibited smaller or no endotherms. The SNPs had higher carboxyl and carbonyl content.