XRD, SEM, and XPS Analysis of Soybean Protein Powders Obtained Through Extraction Involving Reverse Micelles

Soybean protein powders obtained by aqueous buffer and reverse micelle extractions were examined and characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). These analysis methods provided detailed information about elemental distributions, surface structure, and secondary and microstructures of the protein, respectively. XPS data revealed that the O and N atomic percentages of soybean protein surfaces obtained with bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/hexane reverse micelles were higher than those obtained with aqueous buffer, whereas the percentage of atomic C was lower. The ratios of nitrogen to carbon (N/C) on the surface of soybean protein obtained through the two extraction methods were similar. The O/C ratio for soybean protein obtained from AOT reverse micelles was large. The obtained results indicated that the reverse micelles could affect the C, O, and N components on the surface of soybean proteins. Moreover, XRD and SEM results also showed the influence of AOT reverse micelles, which lead to more beta-sheet and pore structures.