## 3 Results and Discussion
### The Effect of \(S\). aureus Contamination on Metabolites  
A total of 169 metabolites were identified, and the contents of 47 metabolites in fresh dough (Flo), non-contaminated control sourdough (Co16), and contaminated sourdough (S16) were significantly different (\(p<0.05\)) (Table S1). The metabolites with significantly different and \(>\)0.100 g/100 g are shown in Table 1.  
The content of myo-inositol, phosphate, glycolic acid, fructose, sorbitol, glucose, xylose, lactose, \(\gamma\)-aminobutyric acid (GABA), succinic acid, and ribose significantly increased (\(p<0.05\)) during fermentation. The content of 1-kestose, linoleic acid, oxoproline, sucrose, L-Malic acid, and galactinol significantly decreased (\(p<0.05\)) during fermentation. Figure 3: The effect of \(S\). _aureus_ contamination on pH and TTA of sourdough, with Co and S indicating, wholewheat sourdough and wholewheat sourdough artificial contaminated with \(S\). _aureus_ (10\({}^{2}\) cfu/g); \({}^{\mathrm{a,b}}\) means in each bar having different letters are significantly different (\(p<0.05\), \(n=6\)). The myo-inositol are the hydrolysate of phytic acid, which can prevent absorption of minerals such as iron, potassium, magnesium, and zinc and in turn reduce their bioavailability. Flour contains phytases, and several LAB can excrete phytases [4]. The optimal pH of phytases is about 4.3, which is near the pH of sourdough and thus can be beneficial to hydrolysis of phytic acid [1]. The accumulation of glycolic acid during sourdough fermentation might be caused by the conversion of oxalate. Wholewheat flour is rich in oxalate, which can inhibit the absorption of minerals similarly to phytic acid [30]. The xylose and sorbitol are effective prebiotics [21]. Xylose was derived from pentosan hydrolysis; however, arabinose, another product of pentosan hydrolysis, had low content (<0.100 g/100 g, Table S1). This might be due to the fact that arabinose can be easily utilized by LAB and/or _S. aureus_. GABA was reported have several health benefits, such as reducing anxiety, reducing high blood pressure, and improving insomnia [31]. Accordingly, a large amount of literature focuses on developing GABA-enriched foods. Accumulation of GABA during wholewheat sourdough is a new finding of the present study. GABA content has been reported to be about 4.5 mg/100 g in dough and 13.67 \(\pm\) 0.40 mg/100g in sourdough [18]. In this study, the GABA content in wholewheat fresh dough and sourdough were 24.2 \(\pm\) 1.1 and 241 \(\pm\) 17 mg/100 g, respectively. The content of GABA in wholewheat sourdough is higher than not only normal sourdough but also many typical GABA-enriched foods, such as germinated brown rice, which contained GABA 172 mg/100 g in one report [31]. GABA accumulation in wholewheat sourdough occurs partly because many LAB can synthesize GABA [18] and partly because grain bran contains high activity of glutamate decarboxylase (GAD) that can transfer glutamate into GABA [31]. In addition, fermentation reduced the content of atrazine-2-hydroxy (0.003 \(\pm\) 0.005, 0.005 \(\pm\) 0.001, and 0.018 \(\pm\) 0.001 g/100g for S16, Co16, and Flo, respectively), which is the degradation product of atrazine, a common herbicide with a residue limit standard of 0.05 mg/kg (GB 2763-2019, China) [32]; however, there is no limit standard for atrazine-2  
\begin{table}
\begin{tabular}{c c c c} \hline
**Metabolites** & **Flo** & **Co16** & **S16** \\ \hline Fructose & 1.041 \(\pm\) 0.022 b  & 5.225 \(\pm\) 0.432 a [FOOTNOTE:a]Footnote a: The \(\chi\)-dependence of the ratio of the two  
hydroxy. In any case, these results indicate that sourdough fermentation might improve the safety of the dough products. Comparing the Co16 and S16, the content of metabolites that were significantly different (\(p<0.05\)) included glucoheptose, sorbitol, succinic acid, glucoheptonic acid, sucrose, mannose, ribose, and kestose (Table 1 and Table S1). After culturing, the content of mannose in \(S\).