## 3 Results and Discussion
### Dynamic Rheological Properties of Tomato Pomace Powder Suspension
#### 3.3.2 Effect of Non-Isothermal Heating on Tomato Pomace Powder Suspension  
Industrial tomato processing is usually released by hot break (85-95 \({}^{\circ}\)C) or cold break (60-70 \({}^{\circ}\)C). The evolution of complex viscosity (\(\eta^{\star}\)) during non-isothermal heating (20-95 \({}^{\circ}\)C) and subsequent cooling is shown in Figure 3, offering an insight into the thermal stability of suspension samples studied. With an increase in heating, the \(\eta^{\star}\) of each formulated TP suspension followed a different pattern, with the temperature rise at a constant frequency of 1 Hz inducing additional particle thermal motion. This was evidenced with the suspension with 25% TP (T3) which was slightly stiffer than the 20% TP (T2) and 15% TP (T1) suspensions. The stiff effect observed could be related to the thermally induced thickening effects and/or to the presence of pectin [44], a phenomenon quantified by the high value of the complex viscosity. The high concentration of TP and the fact that TP particles have a large specific surface area, exhibiting large bonding affinity to polysaccharides from the suspension, lead to a high value of the complex viscosity. Similarly, [PERSON] and [PERSON] [40] reported that due to the larger surface area of smaller particles, as compared to bigger particles, the interaction forces can increase, determining a raise in viscosity. On the other hand, when large particles form aggregates, occupying more space in the sample than the aggregates of small particles, this leads to a larger volume effectively taken in by these large particles which can also determine an increase in flow resistance [49; 50]. [PERSON] et al. [31] showed that tomato particles in tomato pomace powder ketchup system have a larger specific surface area then particles in fresh tomato pomace ketchup and consequently a larger bonding affinity to polysaccharides. This interconnectivity of particles in tomato pomace powder ketchup system results in a higher value of the complex viscosity relative to fresh tomato pomace ketchup. The suspension with 20% TP (T2) was thermally stable during heating from 25 to 95 \({}^{\circ}\)C, showing a constant value of the complex viscosity with temperature increase, but was softer than T3. The suspension with 15% TP (T1) became more stiffer during cooling than during heating, showing a similar rheological behavior as complex viscosity with the T2 when the cooling temperature decreased under 50 \({}^{\circ}\)C. This fact could be due to the increased TP  
Figure 3: The change of complex viscosity (\(\eta^{\star}\)) during heating and cooling of suspensions containing 15% (T1), 20% (T2) and 25% (T3) tomato pomace powder. particles' affinity to form non-covalent bonds [51]. For all studied suspensions, complex viscosity was higher during cooling relative to heating due to the breaking of particle-polysaccharide bonds which induced a stiffening of the suspensions due to the raised mobility of the particles when the temperature increased. This is in accordance with the results reported by [PERSON] et al. [31]. The higher complex viscosity of the suspension with 25% TP when compared to 15 and 20% TP suspensions suggests its potential applications as a bakery filling. Yield stress values obtained for the suspension with 15% (T1), 20% (T2) and 25% (T3) of tomato pomace powder indicated that the transition from elastic behavior to flow was influenced by TP concentration and treatment temperature (Figure 4). Tomato pomace, containing a high amount of fiber, such as cellulose and pectic substances [7], influences the yield stress. The results showed that by increasing the particle concentration, the yield stress was increased. These findings are in accordance with those reported in several studies [49; 52]. Apart from the amount of suspended particles, particle deformability can also affect the rheology of suspensions. A higher yield stress has been reported for less deformable particles [37; 53].