The phase properties of soy protein and wheat gluten in a blend for fibrous structure formation

Summary

Fibrous macrostructures can be obtained from among others soy protein isolate (SPI) - wheat gluten (WG) blends, when deformed with simple shear flow while heating. This SPI-WG blend consists of two phases, which are separated on a micrometer scale. The properties, especially the rheological properties, of SPI- andWG-phases determine the structure formation process largely. The objective of this study was to determine the properties of the phases present in SPI-WG blends using conditions relevant for fibrous structure formation. Since, the rheological properties are dependent on the concentration of each protein
in its respective phase, we determined the water content in the two phases with a methodology based on time-domain nuclear magnetic resonance. The spatial distribution of the two phases was studied with confocal scanning laser microscopy, and the rheological properties were measured with three types of
oscillatory rheology. The experiments showed that the SPI-phase absorbed more water than the WGphase, which resulted in a larger volume fraction than mass fraction of the SPI-phase and vice versa for WG. The absorption of more water by SPI resulted in a lower concentration of SPI in that phase, remarkably leading to a G0-value for SPI that was similar to the rheological properties of WG. Similarities
in rheological properties seem to be required to strongly deform and align the dispersed phase and form fibrous macrostructures.