## 3 Results and Discussion
### Dynamic Rheological Properties of Tomato Pomace Powder Suspension
#### 3.3.1 Effect of Concentration and Temperature on Dynamic Rheological Properties
The suspensions exhibited predominantly solid-like behavior (G\({}^{\prime}<\) G\({}^{\prime\prime}\)) in the studied frequency range, with G\({}^{\prime\prime}\) lower than G\({}^{\prime}\) by less than 10-fold [38]. As it can be seen in Figure 1c, the 25% TP concentration resulted in the maximum mechanical rigidity in the system, a behavior characteristic of a solid-like material such as a network. This can probably be related to the higher amounts of insoluble fibers which could possibly improve the suspension rigidity. To evaluate the frequency dependence of G\({}^{\prime}\) and G\({}^{\prime\prime}\) moduli, experimental data were fitted to a power law model (Equations (5) and (6)) by means of non-linear regression analysis. The results showed that the dynamic rheological moduli represented the experimental data well. The determination coefficient (\(R^{2}\)) had high values for all samples studied (Table 3) which could be explained by the homogeneity of the samples. The consistency indices \(K^{\prime}\) and \(K^{\prime\prime}\) from the model varied in a large range (Table 3), reflecting the magnitude of suspension viscosity in terms of consistency. The consistency increased with the increase in TP concentration in suspensions. An increase in consistency indices with particle concentration has been reported in several studies on the rheology of tomato-derived suspensions [39; 40]. The flow behavior indices \(n^{\prime}\) and \(n^{\prime\prime}\) ranging between 0.068 and 0.272 showed that \(n^{\prime}\) values were much higher than that of \(n^{\prime}\) values (Table 3), indicating a pseudoplastic behavior (\(n<1\)). The rheological behavior of the studied suspensions can be described as that of weak gels and can be attributed to the presence of high molecular weight materials such as pectin. Similar findings that concluded that this behavior corresponded to that of weak gels were reported for tomato paste, ketchup and sauce [41]. Significant differences (\(p<0.05\)) were noticed among samples with different TP concentrations and also among the samples with the same concentration treated at different temperatures. The increase in TP concentration in the suspension system significantly increased (\(p<0.05\)) the consistency and the flow behavior indices, \(n^{\prime}\) and \(n^{\prime\prime}\) in all tested suspensions except the samples at 25% TP concentration treated at 20 \({}^{\circ}\)C and 95 \({}^{\circ}\)C. As it can be observed from Table 3, for the same TP concentration in suspension, the values of \(K^{\prime}\) and \(K^{\prime\prime}\) increased as the temperature treatment was raised, the highest value being registered at 95 \({}^{\circ}\)C. For the same concentration, compared with the sample at 20 \({}^{\circ}\)C, the \(n^{\prime}\) and \(n^{\prime\prime}\) indices increased significantly at 60 \({}^{\circ}\)C and then, at 95 \({}^{\circ}\)C decreased. Among all samples treated at 95 \({}^{\circ}\)C, HT3 with the 25% TP concentration was influenced to the greatest measure. Flow behavior indices decreased, while consistency increased for HT3. An increase in elastic and viscous modulus was observed with the increase in treatment temperature, indicating a rise in consistency coefficients at the hot break temperature. These results confirmed the observation reported by [PERSON] et al. [42] who affirmed that temperature had a large effect on the consistency coefficient. At the same time, the samples with 25% TP concentration treated at hot break temperature showed a declining trend with temperature for \(n^{\prime}\) and \(n^{\prime\prime}\) compared to the samples with 20% TP, which indicated that this suspension tended to have a higher plasticity at a higher temperature. Similar results were reported by [PERSON] et al. [43] which showed that an increase in temperature decreased the flow behavior index of some commercial ketchup.