## 3 Results and Discussion  
### General Physicochemical Composition  
The effects of acid addition on the physicochemical properties of cherry wine are presented in Figure 1. In this study, the TAs of all experimental groups were significantly higher than that of the control group, increasing with the increased acid addition, accompanied by a pH level decrease as well. Among the groups, the LC group showed a higher TA than the other groups, while the changes in pH value were slight, decreasing from 4.14 to 4.06 when the initial TA increased from 3.50 to 5.45 g/kg. In contrast, the pH levels of MC and MLC varied widely, decreasing from 4.29 to 4.02 and 4.30 to 3.98, respectively. It is interesting that the MC and MLC groups showed higher pH levels when the initial TAs were 3.50 and 4.15 g/kg, while these levels became significantly lower than in the LC group as the initial acid concentration increased. The initial acid concentration and kinds of acid were probably the important factors affecting wine fermentation. The addition of malic acid leads to a more sufficient malotactic fermentation and is accompanied by the increase in pH level, which is caused by the conversion between C4 dicarboxylic malic acid and C3 monocarboxylic lactic acid [9]. However, the malolactic fermentation is limited by the excessive acids, and the excessive organic acid is the main reason for the pH decreasing, and the various organic acid profiles in cherry wine result in different pH values after fermentation [32]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Temperature Gradient** & \
\begin{tabular}{c} **Temperature Rate** \\ (\({}^{\circ}\)**C/min**) \\ \end{tabular} & **Temperature (\({}^{\circ}\)**C**)** &
\begin{tabular}{c} **Maintained** \\ **Time (min)** \\ \end{tabular} & **Total Run Time (min)** \\ \hline Initial & & 33 & 1 & 1 \\
1 & 3 & 78 & 2 & 18 \\
2 & 3 & 90 & 2 & 24 \\
3 & 3 & 99 & 2 & 29 \\
4 & 3 & 140 & 1 & 43.667 \\
5 & 6 & 160 & 1 & 48 \\
6 & 8 & 220 & 2 & 57.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The oven temperature program for GC-MS analysis. Figure 1: The physicochemical parameters of wine samples with different organic acid treatments. (**A**) pH and titratable acidity; (**B**) ethanol; (**C**) residual sugar; (**D**) volatile acidity; (**E**) dry extract. Difference lowercase letters represent significant difference (ANOVA, \(p<0.05\)). (In the MC-3.50, MC-4.15, MC-4.80 and MC-5.45 groups, respectively, the initial acid contents of the cherry must were adjusted to 3.50, 4.15, 4.80 and 5.45 g/kg by using malic acid; in the MLC-3.50, MLC-4.15, MLC-4.80 and MLC-5.45 groups, they were adjusted by the mixture of malic acid and lactic acid; in the LC-3.50, LC-4.15, LC-4.80 and LC-5.45 groups, they were adjusted by lactic acid). In addition, the change in pH caused by acid addition could significantly affect other physicochemical parameters of wines [33]. In this research, the acidification did not affect the sugar consumption but significantly affected the ethanol content, volatile acidity and dry extract of wine. Organic acid addition significantly reduced the volatile acidity of cherry wines (0.63-0.99 g/L), and caused it to be less than the acceptable limit (1.2 g/L acetic acid equivalents) according to OIV [34]. Moreover, these groups also showed higher alcohol content and more dry extract than the control. During wine fermentation, the sugar was mainly utilized by yeast and converted into ethanol. The constant sugar consumption indicated that the addition of organic acid did not affect the activity of yeast. Volatile acid is basically derived from acetic acid, which is produced from ethanol by acetobacteria metabolism [35]. And the decrease in volatile acids and increase in ethanol in the acid treatment groups might be caused by the decrease in the initial pH value of cherry must, which could inhibit the growth of acetic acid bacteria [36]. By contrast, MC-3.5, MC-4.15, MLC-3.5 and MLC-4.15 presented higher volatile acidity and lower alcohol content than the LC group.