Characterization of Soy Protein Nanoparticles Prepared by High Shear Microfluidization

Abstract

Soy protein nanoparticles were produced with a microfluidizer and characterized in terms of particle size, size distribution, morphology, rheological properties, and aggregate structure. Three stages of structure breakdown were observed when the soy protein dispersion was passed through the microfluidizer. A sudden change in the aggregate size was observed after a certain number of passes through the microfluidizer; such change was both concentration and pH dependent. Rheological measurements of these soy protein emulsions showed that both viscosity and storage/loss modulus decreased as the aggregate size of soy protein was decreased, indicating reduced interactions between the aggregates. The fractal dimension of the soy protein aggregates was estimated from the properties of a continuous matrix embedded with the aggregates.

Keywords:

• Microfluidizer
• nanoparticles
• particle size
• rheological properties
• soy protein

Acknowledgments

This article not subject to US copyright law.

The author would like to thank G. D. Grose for setting up the microfluidizer and A. J. Thomas for conducting the rheological measurements on the soy protein emulsions. Names are necessary to factually report on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.

Notes

Note. Particle sizes of the soy protein emulsions with different concentration and pH after 26 passes through the microfluidizer. D (volume) and D (number) are volume weighted mean diameter and number weighted mean diameter, respectively, from the static light scattering. R_h is the hydrodynamic radius from the dynamic light scattering measurements.

Note. The measurement temperature was 140°C and C = 1.3 was assumed for the connectivity exponent [26] in the equation (3 + C)/(3 − d _f ) = slope. R² is the coefficient of determination, indicating how closely the estimated slopes for the linear lines correspond to the data.