A Comparative Study of Rheological Characteristics of Tomato Paste and Tomato Powder Solutions

The flow curves and time-dependent flow properties of tomato paste and tomato reconstituted solution (TRCS) were assessed in this study at different concentrations and temperatures. The tomato-reconstituted solution was prepared by dissolving the powders (produced by the spray drying technique) in certain amount of water to provide the concentration required. Bingham model was found to be the most appropriate to fit the flow curves of tomato paste. The yield stress, τ B , significantly increased with concentration and decreased with temperature in both the forward- (increasing shear rate) and backward-measurements (decreasing shear rate). The Bingham viscosity, η B , was found to increase with concentration and decrease with temperature. As for the TRCS, the flow curves were also best fitted by the Bingham model with shear stress values significantly less than that of tomato paste at the same concentration and shear rate. Tomato paste solutions showed a time-dependent rheological behavior while the TRCS showed a time-independent behavior. Tomato paste exhibited a thixotropic behavior at low shear rates and converted to an anti-thixotropic behavior at high shear rates.