Rheological properties of tomato ketchup

Anotace: The objective of this paper was to determine the rheological properties especially shear stress and apparent viscosity vs. shear strain rate, and density of commercially available but also homemade tomato ketchup. The effect of tomato content of density and apparent viscosity of tomato ketchup was also described. Shear stress and apparent viscosity were observed in shear strain rates range from 0.1 s-1 up to 68 s-1. All measurements were carried out at a constant temperature of 22 °C. Experimental results were modeled using a power-law (also known as Ostwald-de Waele) model (R2 ranged from 0.9508 up to 0.9991). The flow behaviour of all measured tomato ketchup samples exhibited non-Newtonian pseudoplastic (shear thinning) behavior where the flow index (n) showed values between 0 and 1. Flow index (n) and consistency coefficient (K) can be used especially in numerical simulation of the flow behaviour of pseudoplastic (shear thinning) liquids.