The probing for nanoparticles in soybean protein isolate solutions

Two soybean protein isolates (SPI), one of high (GN) and one of low molecular weight (DN) were prepared. Nanoparticles (NPs) possessing a heterogeneous spatial molecular distribution were verified in both SPI solutions. Spherical GN NPs were larger, more compact, formed more stable bonds between their components, and carried more negative charges when compared with the spherical DN NPs. Upon their dilution, NPs in both solutions underwent various geometrical shape changes via simultaneous particle swelling and dissembling. Their fluorescence spectra revealed bond disruption in NPs, with tryptophan and tyrosine moving to more hydrophobic micro-environments when the solutions were diluted 10 times. All aforementioned results were further corroborated by measurements of filtered samples. The NPs property differences between the two SPIs species shed light on their distinct fates during the extrusion process. This study offers new insights in establising criteria for raw materials selection in the food industry. [Display omitted] •Two types of soybean protein isolate (SPI), GN and DN, were prepared.•The existence of nanoparticles (NPs) in SPI solutions was verified.•NPs of these two SPI were distinctive by their shape, size and charges.•NPs show heterogeneous spatial macromolecular distributions.