## 3 Results and Discussion
The use of marigold powder at a level of 2% and 4% did not significantly affect the cooking loss and water absorption of the noodles after cooking, respectively. However, the samples prepared with a high level of marigold powder exhibited higher cooking loss and lower water absorption. The decreased water absorption of the noodles with marigold powder could be correlated with the reduced pasting parameters, specifically peak viscosity, which is known to be closed related to starch swelling volume [25]. Figure 3: Microstructural changes of wheat flour pastes by marigold powder (\(\times\)1000 magnification). These results were closely correlated with the structural characteristics of the noodles with marigold powder (see Figure 3). Table 1 shows the effect of marigold powder on the textural properties of marigold-powder-incorporated wheat noodles, which were measured using a Kieffer dough and gluten extensibility rig. After cooking, the maximum resistance required to extend noodles (Rmax) and the distance at the maximum force (E) [26] were evaluated. The control sample without marigold powder had the highest value of Rmax (1.74 N) and E (19.14 mm), whereas the use of marigold powder for the wheat flour significantly reduced values of both Rmax and E. However, when marigold powder was incorporated at a level of 2% (\(w/w\)), there were no significant differences in the tensile properties (Rmax) from the control sample. The HPLC analysis demonstrated that the level of lutein in the marigold powder was determined to be 2.639% (data not shown). This result could be favorably compared with the lutein contents of the different marigold cultivars in preceding studies, which were reported to be in the range of 0.831-2.059% for the petals [27] and 0.126-0.272 for the flowers [28]. The levels of lutein in the marigold-powder-incorporated fresh noodles were quantitatively analyzed before and after cooking using the HPLC. As shown in Figure 5, the contents of lutein in the noodles increased when the amounts of marigold powder were increased, whereas lutein was not detected in the control noodle sample made from wheat flour without marigold powder. Before cooking, the levels of lutein in the noodles prepared with marigold powder ranged from 61.2 to 204.9 mg/100 g noodle. After cooking, the levels of lutein in the noodles decreased to 37.1-144.6 mg/100 g noodle. Thus, the cooking process led to a distinct decrease in the content of lutein by almost 50%. This could be due to the heat labile feature of lutein, which was reported in preceding studies in which the level of lutein in whole grains [29] and vegetable oils [30] was reduced due to exposure to high temperatures. Furthermore, as mentioned in the cooking loss results (Figure 4a), the higher cooking loss of the noodles with marigold powder seemed to cause \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Control** & **2\% Marigold** & **4\% Marigold** & **6\% Marigold** \\ \hline Rmax (N) & 1.74 \(\pm\) 0.15 a & 1.66 \(\pm\) 0.08 a & 1.27 \(\pm\) 0.08 b & 1.11 \(\pm\) 0.09 c \\ E (mm) & 19.14 \(\pm\) 1.46 a & 16.26 \(\pm\) 1.34 b & 15.68 \(\pm\) 0.97 b & 15.06 \(\pm\) 0.79 b \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Effect of marigold powder on the tensile properties of noodles after cooking (means with different letters in the same row differ significantly at \(p<\) 0.05). Figure 4: Effect of marigold powder on the cooking loss (**a**) and water absorption (**b**) of fresh noodles (means with different letters on the bars differ significantly at \(p<\) 0.05). lutein to be reduced. It is recommended to take 10 mg/day of lutein for improving visual functions [31]. Although the levels of lutein in the noodles were reduced after cooking, it appeared that they were enough to satisfy this recommendation. It is widely reported that marigold extracts have great abilities to scavenge radicals [32]. Thus, the effect of marigold powder on the antioxidant capacities of the noodles was examined before and after cooking.