A novel critical point for isotropic gel in rheological-fractal model

The determination of critical point in rheological-fractal models for most of the food gel systems and polymer viscoelastic systems are based on the point of 95% or 90% value of the storage modulus in linear viscoelastic region. It is not a precise method because the modulus during linear-nonlinear viscoelastic transition region are not always monotonous decreasing. Therefore, there is an urgent need for a more stable and precise approach to determine the critical point, making the scaling behavior calculation closer to the physical truth. This research studied on a typical food system, acid-induced peanut protein isolate (PPI) gel, trying to put forward a new critical point for isotropy food gel and non-newton polymer systems. Result shows that when the increasing higher harmonic reaches a certain value, the corresponding strain could be regarded as a new critical strain point. The image of the microstructure captured by confocal laser scanning microscope (CLSM) was used to calculate the actual fractal dimension, which was 2.3517. It was demonstrated that the fractal dimension calculated from rheological fractal model using the new critical strain obtained from the Fourier transform analysis is closer to its actual value (2.3517).