## 3 Results and Discussion
### GC-MS Analysis  
A total of 39 volatile compounds were identified and quantified by using headspace (HS)-SPME/GC-MS, including 20 esters, 7 alcohols, 9 terpen, 1 acid, 1 aldehyde and 1 phenol (Table S3). The concentration histogram of various kinds of VOCs in different cherry wines is presented in Figure 6, and the metabolic differences in VOCs in cherry wines treated by different organic acids were identified using a heatmap (Figure 7). As can be seen in Figure 6, the addition of organic acids had positive effects on the synthesis and release of volatiles. The total contents of VOCs were increased significantly in all treatment groups, among which MC-4.80, MLC-4.80 and LC-5.45 showed the highest enhancements of total VOCs, which increased by 66.92%, 55.04% and 6.83%, respectively. Alcohols and aldehyde were the most abundant VOCs in cherry wine, accounting for 54.88% and 24.08% of the total VOCs in the control. The addition of malic acid and malic-lactic acid significantly affected the metabolism of these two kinds of compounds, and was promoted by the increase in organic acids. Among them, MC-4.80 and MLC-4.80 increased by 93.36%, 36.50% and 67.79%, 63.14%, respectively. Similarly, the addition of lactic acid could also improve the alcohol and aldehyde contents in cherry wine, while the correlation with the usage was not obvious. Moreover, the most interesting observation is that the  
Figure 6: Volatile organic compound concentration histogram of control and different organic acid treatment groups. content of esters increased significantly after adding malic acid and malic-lactic acid, while it decreased in the lactic acid group. Due to the different compositions and concentrations of VOCs in different cherry wines, a hierarchical cluster analysis is presented in Figure 7.  
Alcohols were the largest group of volatiles in all samples. 3-methyl-1-pentanol and benzyl alcohol were the dominant alcohols, accounting for 54.70% and 41.66% in the control group (Table S4), which is in agreement with the results reported by [PERSON] et al. [45]. The concentrations of these two compounds increased significantly when organic acids were used, and the largest increase in 3-methyl-pentanol was detected in MC-4.80, as high as 139.76%, while the cherry wine fermented with malic-lactic acid was distinguished by a higher amount of benzyl alcohol, which increased by 49.94% in MLC-4.80, and which is associated with floral and sweet notes [46]. By contrast, the use of lactic acid resulted in a significantly lower production of these two compounds, which increased by 3.94% and 22.30% in LC-4.80. Moreover, phenylethyl alcohol, which contributes a sweet and rosy flavor to the wine [47], also evidently increased among the tested samples, and the highest concentrations were observed in MC-4.80 (98.66 \(\upmu\)g/L). This indicated that the addition of different organic acids could enhance the concentration of alcohols, while it has no effect on the composition of alcohols. Previous research suggested that alcohols are mainly formed by the deamination and decarboxylation reactions from amino acids [15; 48], and the low pH level of alcoholic fermentation favors the development of more alcohols [33]. Esters are mainly formed from esterification of alcohols with fatty acids during the fermentation and aging process, and are characterized by a fruity and sweet flavor, which significantly contributes to the construction of the characteristic cherry wine aroma [4; 49]. Among the esters, ethyl benzoate, ethyl acetate and ethyl octanoate were the main esters in  
Figure 7: Heatmap visualization of relative differences of volatile organic compounds in cherry wines. The color indicates the level of accumulation of each metabolite, from low (blue) to high (red). the control, accounting for 47.91%, 15.28% and 8.75%, respectively (Table S4). Malic acid and its combination with lactic acid positively influenced the synthesis of ethyl benzoate and ethyl acetate in cherry wine.