Effect of high-pressure homogenization on particle size and film properties of soy protein isolate

High-pressure homogenization (HPH) was used to treat soy protein isolate (SPI) suspensions (7.0%, w/w) in order to reduce SPI's particle size. The obtained suspensions were characterized by studying particle morphology, mean particle size, particle size distribution, zeta potential, rheological properties, and composite film formation. The results showed homogenization pressure and number of homogenization passes had an obvious influence on the mean particle size and the size distribution. The SPI suspension homogenized at 207 MPa from 0 to 30 passes exhibited a shear-thinning behavior, which was accompanied by the reduction of mean particle size from 3331.3 to 135.8 nm. narrower particle size distributions, and increased absolute zeta potentials. Small particle sizes not only improved mechanical and transparent properties, but also reduced water absorption properties for SPI films. However, the reduction of particle size showed little impact on the thermal properties of SPI films. These findings may help better utilization of SPI in the development of novel SPI-based films. (C) 2012 Elsevier B.V. All rights reserved.