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

The effect of heat-denatured whey protein isolate (WPI)/whey protein isolat e (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% (s igma(80)) relative deformation of dWPI/WPI heat-induced gels (14% total pro tein, w/w) was studied. No correlation between the average diameter of aggr egates and the dWPI/WPI ratio, microfluidization pressure, or number of pas ses was found. However, increasing the microfluidization pressure or the nu mber of passes resulted in a narrower size distribution of aggregates. Incr easing the dWPI/WPI ratio and the number of passes resulted in a decrease a nd 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 mo re dissipation of the deformation energy during compression. The positive e ffect 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.