2.2.4. Rheological Behavior of Skim Milk

The viscosities of the control and HA-treated samples were determined using a method described by Sutariya et al. [22] with slight modifications. Viscosity was determined at 10 °C using a rotating rheometer (MCR 92, Anton Paar GmbH, Graz, Austria) using bob and cup assembly. Samples were mixed gently, and 60 mL was poured into a cup (C-CC39, 42.010 mm) fitted with a rheometer and a concentric cylinder attachment (CC39, 38.690 mm), operated by the Anton Paar Rheo Compass 1.20 system. The viscosity was measured over the shear rate profile from 10 to 1000 s⁻¹ where every 3 s the shear rate was increased by 10 s⁻¹. The gap between the bob and cup was kept 5 mm. The viscous behavior of samples was evaluated using the following equation of the Power Law model:

where σ is the shear stress (Pa), K is the consistency coefficient (Pa sⁿ), γ is the shear rate (s⁻¹), and n is the dimensionless flow behavior index that defines the shear thinning or shear thickening properties of a fluid.

To understand the time-dependent behavior of HA polymers in the non-destructive deformation environment, a frequency sweep test was performed using the rheometer over an angular frequency range of 11.5–150 rad/s, at a constant shear strain of 0.5%, at a temperature of 10 °C throughout the experiment.