## 3 Results and Discussion
### UPLC-Q-TOF/MS Analysis  
Non-volatile compound content in wine samples was analyzed by using UPLC-Q-TOF/MS. A total of 49 metabolites were identified (listed in Table S1), including 22 organic acids, 10 amino acids and derivatives, 6 nitrogen glycosides, 5 flavones, 1 anthocyanin and 5 others. The relative concentrations of non-volatile compound contents in different groups \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Total Phenolic Content** & **Total Flavonoid Content** & **DPPH Scavenging** \\  & **(\(\mu\)g GAE/mL)** & **(\(\mu\)g CE/mL)** & **Activity (\%)** \\ \hline Control & 550.90 \(\pm\) 2.92 \({}^{f}\) & 34.00 \(\pm\) 0.30 \({}^{\text{de}}\) & 52.70 \(\pm\) 0.26 \({}^{\text{bc}}\) \\ MC-3.50 & 606.22 \(\pm\) 0.17 \({}^{\text{a}}\) & 38.57 \(\pm\) 0.10 \({}^{\text{c}}\) & 53.14 \(\pm\) 0.49 \({}^{\text{bc}}\) \\ MC-4.15 & 567.56 \(\pm\) 1.03 \({}^{\text{e}}\) & 34.28 \(\pm\) 0.67 \({}^{\text{de}}\) & 50.78 \(\pm\) 0.40 \({}^{\text{de}}\) \\ MC-4.80 & 578.56 \(\pm\) 2.75 \({}^{\text{cd}}\) & 34.10 \(\pm\) 2.05 \({}^{\text{de}}\) & 46.90 \(\pm\) 1.11 \({}^{\text{f}}\) \\ MC-5.45 & 577.35 \(\pm\) 0.86 \({}^{\text{d}}\) & 30.23 \(\pm\) 2.03 \({}^{\text{f}}\) & 47.32 \(\pm\) 0.94 \({}^{\text{f}}\) \\ MLC-3.50 & 574.26 \(\pm\) 3.95 \({}^{\text{d}}\) & 35.55 \(\pm\) 0.28 \({}^{\text{d}}\) & 48.97 \(\pm\) 1.12 \({}^{\text{de}}\) \\ MLC-4.15 & 589.38 \(\pm\) 0.17 \({}^{\text{b}}\) & 44.45 \(\pm\) 3.35 \({}^{\text{a}}\) & 57.92 \(\pm\) 4.07 \({}^{\text{a}}\) \\ MLC-4.8 & 582.68 \(\pm\) 5.84 \({}^{\text{c}}\) & 31.45 \(\pm\) 0.25 \({}^{\text{ef}}\) & 46.81 \(\pm\) 0.69 \({}^{\text{f}}\) \\ MLC-5.45 & 528.56 \(\pm\) 2.92 \({}^{\text{g}}\) & 30.15 \(\pm\) 0.08 \({}^{\text{f}}\) & 48.06 \(\pm\) 3.42 \({}^{\text{ef}}\) \\ LC-3.50 & 591.79 \(\pm\) 0.86 \({}^{\text{b}}\) & 42.16 \(\pm\) 1.45 \({}^{\text{ab}}\) & 57.83 \(\pm\) 0.32 \({}^{\text{a}}\) \\ LC-4.15 & 598.99 \(\pm\) 4.47 \({}^{\text{b}}\) & 41.10 \(\pm\) 3.90 \({}^{\text{bc}}\) & 55.36 \(\pm\) 1.23 \({}^{\text{ab}}\) \\ LC-4.80 & 577.87 \(\pm\) 1.03 \({}^{\text{cd}}\) & 34.41 \(\pm\) 0.31 \({}^{\text{de}}\) & 53.10 \(\pm\) 0.16 \({}^{\text{bc}}\) \\ LC-5.45 & 552.27 \(\pm\) 0.52 \({}^{\text{f}}\) & 34.28 \(\pm\) 0.27 \({}^{\text{de}}\) & 51.85 \(\pm\) 1.37 \({}^{\text{cd}}\) \\ \hline \hline \end{tabular} Note: Different lowercase letters in the same column represent significant differences (ANOVA, \(p\) < 0.05). (MC: malic acid; MLC: malic acid and lactic acid; LC: lactic acid; ANOVA: analysis of variance).  
\end{table} 
Table 5: Total phenolic content, total flavonoid content and antioxidant activity of cherry wine with different organic acid treatments. The application of malic acid before fermentation produced different effects on 4 types of compounds, including 4 organic acids (malic acid, citric acid, maleic acid and lactic), 2 amino acids and derivatives (L-tryptophan and aspartic acid), 2 nitrogen glycoside (uridine and dihydroxacil) and 1 other (phenylacetaldehyde) (Figure 2A). Compared with the control, the contents of malic acid in cherry wine did not change significantly when the initial acid content was no more than 4.15 g/kg, while it increased significantly after the initial acid content adjusting to 4.80 g/kg (Figure 2B). It indicated that the utilization of malic acid was less than its addition in MC-4.80, and resulting in the accumulation of malic acid. In addition, it was found that the content of citric acid and maleic acid also increased, while the content of lactic acid decreased. However, the consumption of amino acids and nitrogen glycoside were increased as the increasing of malic acid addition (Figure 2B). It indicated that the organic acid metabolism was affected by excessive malic acid addition, but had no effect on strain activity during fermentation. Instead of that, the utilization of nitrogen source was promoted by higher malic acid addition.