Hydraulic characteristic of collagen

Hydraulic characteristic of collagen. Czech J. Food Sci., 33: 479–485. The hysteresis of a hydraulic characteristic while pumping an aqueous solution of collagen through a pipe at gradually increasing and decreasing flow rates (hysteresis means that the pressure drop curve during increased flow rate is above the pressure drop during decreasing flow rate) was observed. The problem was initiated by industry and by demand for an on-line recording of rheological properties of collagenous material used for extrusion of collagen casings. The Herschel-Bulkley rheological model was capable to describe rheograms in a wide range of deformation rates; however it was not able to describe and explain the hysteresis. As a possible reason thixotropic properties were identified and the hydraulic characteristic was calculated using a thixotropic generalisation of the Herschel-Bulkley model. The developed 1D numerical model can be applied for on-line modelling of transient flows of incompressible thixotropic food materials (startup flow) and at a limited range of flow rates it is also capable to describe the hysteresis of hydraulic characteristics.