## 3 Results and Discussion
### Organic Acid Analysis by HPLC  
The total organic acid content was analyzed using HPLC, revealing a significant increase in the total organic acid levels in SY and KB samples during the first two days of fermentation (_p_ < 0.05). This initial surge was primarily due to the high nutrient content in the mash, which promoted the rapid growth of acid-producing microbes (Table 1). During the mid-fermentation period (days 2 to 8), the rate of increase in organic acid content for both SY and KB samples slowed. This deceleration can be ascribed to the increased alcohol concentration and decreased pH, which inhibited the growth and metabolism of certain acid-producing microorganisms. From days 5 to 8, fluctuations in total organic acid content were observed, mainly due to the introduction of exogenous strains (_P. anomala_ on day 5 and _L. plantarum_ on day 8). In the late fermentation stage (days 9 to 15), the organic acid content in SY and KB samples exhibited an upward trend. At the end of fermentation, SY had an overall organic acid content of 8.43 g/L, significantly higher than the 7.58 g/L observed in KB (_p_ < 0.05). This increase indicates that the addition of exogenous strains, especially the _L. plantarum_ with its strong ability to produce lactic acid, enhanced the organic acid content in the later fermentation stages, promoting ester synthesis and thereby enhancing the stability and quality of the baijiu [36; 37]. The organic acids in the SY and KB samples were analyzed, focusing on acetic acid, malic acid, succinic acid, and lactic acid. These acids accounted for 86.83% and 79.82% of the total organic acids in the SY and KB samples, respectively. This indicates that lactic acid, succinic acid, acetic acid, and malic acid, with their higher concentrations, were the predominant organic acids in the CFB. Together, they contributed significantly to the primary acidic flavor compounds, further promoting the production of esters, which was in accordance with the findings of our previous study [31]. In particular, the acetic acid concentration in the KB sample was 1.402 g/L, notably higher than the 1.212 g/L observed in the SY sample at the end of fermentation (Table 1). The malic acid content rose throughout fermentation in both groups, reaching 1.586 g/L in SY and 1.374 g/L in KB (Table 1). Additionally, the succinic acid content in both samples gradually increased during fermentation, with the SY sample showing a higher concentration of 1.855 g/L compared to 1.642 g/L in the KB sample at the end of fermentation. During the early fermentation stages, the lactic acid content rose quickly in both groups (Table 1). This rise was due to the conversion of pyruvate acid from glycolysis into \begin{table}
\begin{tabular}{c c c} \hline \hline
**Organic Acids** & **Chi-Flavor Baijiu (mg/L)** &
\begin{tabular}{c} **Fermented 15 d with _P. anomala_** \\ **and** _L. plantarum_ **(mg/L)** \\ \end{tabular} \\ \hline Acetic acid (A) & 1402.25 \(\pm\) 19.24 \({}^{\text{g}}\) & 1212.09 \(\pm\) 31.79 \({}^{\text{h}}\) \\ Malic acid (B) & 1373.95 \(\pm\) 9.99 \({}^{\text{g}}\) & 1585.81 \(\pm\) 15.23 \({}^{\text{t}}\) \\ Succinic acid (C) & 1642.16 \(\pm\) 49.12 \({}^{\text{t}}\) & 1854.89 \(\pm\) 59.93 \({}^{\text{e}}\) \\ Lactic acid (D) & 2165.59 \(\pm\) 45.58 \({}^{\text{c}}\) & 2081.14 \(\pm\) 27.40 \({}^{\text{d}}\) \\ Total organic acids & 7582.95 \(\pm\) 83.21 \({}^{\text{b}}\) & 8435.17 \(\pm\) 76.30 \({}^{\text{a}}\) \\ \hline \hline \end{tabular} Values were shown as the mean \(\pm\) SE (n = 3). Different letters within the same column indicate significant differences by Tukey-Kramer multiple comparison test (_p_ < 0.05).  
\end{table} 
Table 1: Changes in organic acid contents during CFB fermentation. lactic acid by lactic dehydrogenase in lactic acid bacteria, with such genera as _Lactobacillus_, _Pedicoccus_, and _Weissella_[38]. At the end of fermentation, the lactic acid content in the SY and KB samples was 2.081 g/L and 2.166 g/L, respectively.