Uniaxial compression of thermal gels based on microfluidized blends of WPI and heat-denatured WPI

The effect of heat-denatured whey protein isolate (dWPI)/whey protein isolate (WPI) ratio (0-0.6), microfluidization pressure (0-1000 bar), and number of passes (1-10) on the uniaxial shear stress at 10% (sigma(10)) and 80% (sigma(80)) relative deformation of dWPI/WPI heat-induced gels (14% total protein, w/w) was studied. No correlation between the average diameter of aggregates and the dWPI/WPI ratio, microfluidization pressure, or number of passes was found. However, increasing the microfluidization pressure or the number of passes resulted in a narrower size distribution of aggregates. Increasing the dWPI/WPI ratio and the number of passes resulted in a decrease and an increase of gel hardness, respectively. The results were interpreted in terms of more random aggregation/gelation of proteins in the presence of aggregates that could result in localized heterogeneities into gels and more dissipation of the deformation energy during compression. The positive effect of the number of passes on the gel hardness was also considered to be due to a more homogeneous aggregation/gelation of proteins in the presence of smaller aggregates.