## 3 Results and Discussion
### Detection of Yeast and Mold  
Mold growth affects the shelf life of baked goods and is also the main cause of spoilage [55; 56; 57]. The breads were sliced and stored at room temperature, and the yeast and mold growth are shown in Figure 3. No yeast or mold was detected in any groups from the first to the fourth day of storage. The yeast and mold counts of the 4-8% SPI-fortified breads on the fifth day were 4.06 log CFU g\({}^{-1}\), 4.23 log CFU g\({}^{-1}\), and 3.57 log CFU g\({}^{-1}\), respectively. A possible reason could be the pH values of the 4-8% SPI-fortified breads (Figure 2C), which were 5.52, 5.69, and 5.83, respectively. Comparatively, the control (pH = 5.14) and the 2% SPI-fortified bread (pH = 5.34) were slightly more acidic and more unfavorable for mold growth. On the sixth day of storage, the yeast and mold counts of the control and the 2% SPI-fortified bread were 4.69 log CFU g\({}^{-1}\) and 4.29 log CFU g\({}^{-1}\), respectively. From the sixth day onwards, mycelia and dark patches, discernible with the naked eye, were observed on the sliced surfaces of the breads. The yeast and mold counts of the 4-8% SPI-fortified breads were 5.43 log CFU g\({}^{-1}\), 4.90 log CFU g\({}^{-1}\), and 4.57 log CFU g\({}^{-1}\), respectively. The yeast and mold colonies continued to grow on the seventh  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Group** & **Appearance** & **Taste** & **Softness/Hardness Texture** & **Overall Acceptance** \\ \hline Control & 6.37 [FOOTNOTE:]Footnote : The name of the control was 6.84 while those of the 2%, 4%, 6%, and 8% SPI-fortified breads were 6.02, 5.84, 4.88, and 4.22, respectively. The score of the control was 6.84 while those of the 2%, 4% SPI-fortified breads were 6.14, 5.56, 4.94, and 3.82, respectively. \\ \hline
8\% & 4.33 [FOOTNOTE:]Footnote : The name of the control was 6.84 while those of the 2%, 4%, 6%, and 8% SPI-fortified breads were 6.14, 5.56, 4.94, and 3.82, respectively. \\ \hline \hline \end{tabular}
\end{table}
Table 3: Consumer preferences toward breads made by partially substituting high-gluten flour with soy protein isolate.  
day, on which the mold counts of the control, 2%, 4%, 6%, and 8% SPI-fortified breads were 5.58 log CFU g\({}^{-1}\), 5.44 log CFU g\({}^{-1}\), 6.95 log CFU g\({}^{-1}\), 6.15 log CFU g\({}^{-1}\), and 5.77 log CFU g\({}^{-1}\), respectively. Additionally, soy protein has a higher water retention capacity, as exemplified on the sixth and seventh days, when the moisture contents of the SPI-fortified breads were significantly higher than that of the control (Figure 2A). This could be a reason why the yeast and mold counts of SPI-fortified breads were higher than those of the control.  
Baking inhibits the growth of mold and mold spores in bread. Mold growth is caused by recontamination after baking, such as during the cooling, slicing, packaging, and storage processes. Bread is contaminated when exposed to mold spores in the air, and the surface of sliced bread is an ideal environment for mold growth. Therefore, the experimental environment in this study may have affected mold growth on the bread. However, under the same conditions, yeast and mold were only detected in the 4% SPI-fortified bread from the fourth day of storage onwards, while they were only detected in the control and 2% SPI-fortified breads on the fifth day. Thus, SPI use exceeding 4% in bread promotes faster yeast and mold growth.