In this work, a new model for viscosity decay at constant shear rate is tested and the thixotropic behavior of representative food products is experimentally analyzed. The equilibrium viscosity (or steady‐state viscosity) of some food products, obtained after a sufficiently long time of shear at a constant shear rate, is found to be well represented by the Herschel‐Bulkley model and by an exponential model in which a maximum of two terms of an infinite series are required. The model for viscosity decay, that is, the decrease in viscosity with time at constant shear rate, assumes nth
order kinetics for the decay of a structural parameter λ. The rate constant k
, for the decay of λ, is found to be a power law function of the shear rate. The equation for structure decay is combined with a scalar constitutive equation for the shear stress and the resulting model represents adequately the data for viscosity decay of foodstuffs in the range of shear rates 50<<5420 s−1.
Data for suspensions such as tomato juice are observed not to follow the expected structural breakdown behavior. Experimental hysteresis curves show that no consistent pattern between shear stress and maximum rate (0)
or time (t0)
to reach 0
was found, making it impossible to use the information from the viscosity decay experiments to predict the results of the hysteresis experiments.