Rheological Characterization of a Low‐Concentration Water‐Based Collagen Dispersion Under Extensional, Shear, and Oscillatory Deformation

ABSTRACT This study presents an investigation of the extensional, shear, and oscillatory rheological behavior of a 3 wt% native bovine collagen dispersion using capillary rheometer and oscillatory shear testing. Extensional viscosity was determined from the entrance pressure drop using Cogswell's analysis. The entrance pressure drop was obtained through both Bagley extrapolation and orifice die methods. The close agreement between Bagley and orifice die results confirms the reliability of the entrance pressure measurements and indicates that the fabricated orifice die can be used for direct entrance pressure drop determination within the investigated range. The collagen dispersion exhibited pronounced shear thinning and extensional thinning behavior. The apparent shear viscosity () decreased from approximately 250 Pa·s to 6.3 Pa·s while the extensional viscosity () decreased from approximately 1.6 × 10 6 Pa·s to 3.4 × 10 4 Pa·s over the investigated deformation rate range. Small and large amplitude oscillatory shear (SAOS and LAOS) measurements showed solid‐like viscoelastic behavior in the linear regime and nonlinear viscoelastic behavior at large strain amplitudes. Fourier transform (FT) rheology results showed a progressive increase in higher harmonic contributions with increasing strain amplitude. Results are relevant for the design and optimization of collagen‐based food, biomedical, and extrusion processes.