Surface roughness and textural image analysis, particle size and stability of microparticles obtained by microfluidization of soy protein isolate aggregates suspensions

Protein microparticles are of interest in the development of low-fat foods and as stabilizing agents of food dispersed systems. The characteristics of the microparticles influence food texture, so that it is important to consider the processing conditions for their production. In this work, soy protein isolate (SPI) aggregates obtained by heat treatment (93 °C for 15 min) and di_erent pH values (3, 5, 7 and 9) were subjected to microfluidization (110 MPa, 1, 2 or 3 cycles). The resulting SPI suspensions were evaluated for particle size, zeta potential and Turbiscan stability index (TSI). The TSI of SPI microparticles suspensions (TSI) was better at pH 9 (and 1 MF cycle) due to the distance from the average isoelectric point for soy proteins (4.5). By atomic force microscopy it was possible to observe the breakdown of the aggregates. In all cases, a decrease in height’s profiles was observed after MF, which confirmed the reduction in particle size of the microparticles. Surface roughness and image texture analyses allowed to evaluate the e_ect of MF on the surface of the microparticles. The best descriptor of the image texture characteristics of microparticles was the second angular moment while the rest of the descriptors did not correlate with the characteristics of the images in the whole range of operating conditions given that their calculation algorithms were not sensitive enough to detect the small variations in image texture of the samples.