Rheological properties of fruit purees: Effect of cooking

The rheological behaviour of different fruits (raspberry, strawberry, peach and prune), fresh or cooked, was determined using a rotational viscosimeter which allowed experiments to be conducted at different temperatures. The experiments were carried out at temperatures ranging from 20 to 40 °C. The shear rate values ranged from 17.8 to 445 s−1. The results were analysed by employing two different rheological models; Ostwald Waele and Herschel–Bulkley, and both of them fitted reasonably well the experimental data at all temperatures (R2 > 0.998). Linear models were proposed to correlate the rheological parameters and temperature. The experimental measurements showed that the fruit purees studied have a non-newtonian behaviour and the apparent viscosity is influenced by the cooking.