## 3 Results and Discussion  
Figure 1a exhibits the pasting patterns of the wheat flour containing marigold powder. The pasting profiles of all the samples were distinctly characterized by peak viscosity during heating, a decrease in the viscosity during the temperature holding, and a viscosity increase during the cooling. This pasting pattern could be explained by the fact that starch granules in the wheat flour became swollen and ruptured during gelatinization and then recrystallized during retrogradation [19]. Therefore, as the wheat flour was replaced with marigold powder, the pasting parameters such as peak, through, and final viscosities became lower, which would be due mainly to the reduced level of starch granules derived from the wheat flour replacement with marigold powder. This pasting trend was also observed in preceding studies where wheat flour was replaced with corn bran [20] and \(\beta\)-glucan [21]. The effect of marigold powder on the thermal properties of the wheat flour was investigated as shown in Figure 1b. A distinct peak of starch gelatinization was clearly detected in the temperature range from 60 to 70 \({}^{\circ}\)C. The values of the peak enthalpy required to gelatinize the starch granules in the wheat flour tended to decrease with increasing amounts of marigold powder. However, as can be seen in Figure 1b, the use of marigold powder did not significantly influence the gelatinization temperature of the wheat flour (\(p>0.05\)). The changes in the dynamic viscoelastic properties of wheat flour paste due to marigold powder were examined. Figure 2 showed the storage (G\({}^{\prime}\)) and loss (G\({}^{\prime\prime}\)) moduli of the paste samples, which are measures of the elastic and viscous nature of a material, respectively [22]. They had a tendency to increase when the frequency increased, showing frequency dependence. In addition, all the samples had higher values of storage moduli (G\({}^{\prime}\)) than loss moduli (G\({}^{\prime\prime}\)), which indicated a predominant elastic behavior. Thus, all of the samples exhibited weak-gel-like viscoelastic characteristics. It was also noted that the values of G\({}^{\prime}\) and G\({}^{\prime\prime}\) decreased with increasing levels of marigold powder. These results showed that the replacement of the wheat flour with marigold powder weakened the structure of the paste samples, consequently contributing to the reduced viscoelastic parameters. Figure 1: Effect of marigold powder on the pasting (**a**) and thermal (**b**) properties of wheat flour (means with different letters in the same column differ significantly at \(p<0.05\)). Figure 2: Changes in the viscoelastic properties of wheat flour pastes by marigold powder (G\({}^{\prime}\) (**a**) and G\({}^{\prime\prime}\) (**b**)). The microstructure of the starch paste samples with marigold powder was investigated using scanning electron microscopy. Figure 3 shows the three-dimensional structure of the paste samples with the different levels of marigold powder, exhibiting a cellular structure [23]. The paste sample without marigold powder appeared to have a dense and tight structure. However, the pores became larger in the paste samples with higher levels of marigold powder, probably weakening the structural network. Therefore, it appear that these structural changes with the addition of marigold powder were correlated with the reduced viscoelastic parameters as already mentioned in Figure 2.  
The cooking properties of the noodles prepared with marigold powder were investigated, and results are shown in Figure 4. It is well-recognized that solid components in noodles are released to cooking water when the noodles are cooked in hot water, consequently leading to a cooking loss [24]. Since a high cooking loss is related to a sticky noodle texture and viscous liquid, the cooking loss is recognized as one of important quality measures for noodles. Figure 4 shows the effect of marigold powder on the cooking properties of the noodles cooked for 3 and 6 min.