Newtonian viscosity behavior of dilute solutions of polymerized whey proteins. Would viscosity measurements reveal more detailed molecular properties?

Dilute solution Newtonian viscosity of whey protein polymers at different temperatures has not been assessed in literature. In this work, a thermally-treated whey protein solution at 8% w/w and pH 6.8 was prepared. Dilute solution viscometry was investigated at different temperatures from 30 °C to 65 °C. Intrinsic viscosity and voluminosity data indicate slight shrinkage in molecular size upon temperature increase. The temperature dependence of viscosities was expressed by the Arrhenius–Frenkel–Eyring equation and the thermodynamic parameters of viscous flow of polymer solutions were calculated. Results show a positive entropy change of viscous flow, indicating ordered structures. Chromatographic separation results prove that although disulphide bonds form the polymer backbone chain, both hydrophobic associations and hydrogen bonding still play a role in molecular structuring, even at very low protein concentrations. The calculated shape factor indicates spherical polymer molecules over the entire investigated temperature range.