A New Model to Describe Flow Behaviour of Concentrated Orange Juice

The knowledge of rheological behaviour of juices and fruit derivatives is very useful both in the prediction of their stability and in process design, and it depends on the type of juice and on the raw material with which they are produced. Most of the equations that have been used to quantify flow behaviour describe the evolution of shear stress with the change of shear rate. Nevertheless, the essential variable in equipment design is viscosity. In this way, a mathematical model to easily describe the evolution of apparent viscosity of these non-Newtonian fluids with the shear rate would be very useful. In this work, a mathematical expression has been developed, fitted to experimental data and compared with the Herschel–Bulkley one. The obtained parameters with concentrated orange juice followed these trends: equilibrium apparent viscosity (η _∞) scarcely changed with temperature. Static apparent viscosity (η ₀) decreased with increasing temperature, contrary to what happened with the flow behaviour constant k.