Effect of high speed shear on the non-linear rheological properties of SPI/κ-carrageenan hybrid dispersion and fractal analysis

Abstract

In this research, the effect of shear rate (rotation speed) of high speed shear treatment on the linear and non-linear rheological properties and microstructure of soy protein isolate (SPI)/κ-carrageenan (κ-KARA) hybrid dispersion was studied. It is found that high-speed shear treatment makes the hybrid system more homogeneous in a certain shear rate range (around 6000N) within which the mixing effect is stronger than the shearing effect on the mixed system. However, the elastic (G′) and viscous properties (F′) of the hybrid system increase when the shear rate is above a certain range (over 8000N). The effect of the destruction of the hybrid system structure becomes gradually greater (G’ decrease) than the effect of the mixing, resulting in a decrease of the storage modulus and apparent viscosity. The result of the LAOS test shows that the shear rate only affects the magnitude of the I3/1 peak and does not have a significant effect (p < 0.05) on the peak strain value. In other words, the shear rate only has a significant effect on the influence of higher harmonics. The trend of the Lissajous curve shows that the elasticity of the hybrid system dispersion increases with increasing shear rate. The microstructure and fractal analysis shows that with the increase in the high speed shear rate, the fractal dimension of the mixed system solution increases significantly (p < 0.05), indicating that the degree of chaos of the hybrid system dispersion increases with increasing shear rate.