## 3 Discussion  
The study suggests that the effect of cold soak on aroma compounds is dependent on the grape variety, which is consistent with the previous research [23; 24], and the leaching rates are affected by the levels of aroma compounds in grape berries. Generally, C6 alcohols, terpenes and norisoprenoids were the main compounds that caused differences in the berries of 'Marselan' and 'Merlot' grapes. The concentrations of terpenes and norisoprenoids increased during the maceration stage, but their leaching rate was positively correlated with their concentrations in the grapes. Similar patterns were observed for some C6 compounds, such as glycosidically bound (_E_)-2-hexen-1-ol and 1-hexanol, as well as free-form (_Z_)-3-hexen-1-ol. However, other C6 compounds showed continuous increasing or decreasing trends and did not differ between the varieties. During the fermentation and bottle storage stages of dry red wine, the aroma changes mainly occur in esters. Yeast alcohol fermentation produces a large number of aroma compounds, mainly being acetates and straight-chain acid ethyl esters. MaloAlactic fermentation mainly produces branched acid ethyl esters, such as ethyl 2-methylbutyrate, ethyl 3-methylbutyrate, heptyl acetate and others. The compounds exhibited an increasing trend, which is consistent with the findings of previous reports [25; 26]. Citronellol and linalool were the primary monoterpenoids detected in the two stages. Citronellol, an essential monoterpenoid compound in wine grapes, has a delightful aroma of rose and citrus. Due to its low sensory threshold, citronellol significantly impacts the aroma profile of wine [3]. During the fermentation and bottle storage, the concentration of citronellol continued to decrease, which was opposite to that of linalool, another monoterpenoid. Research has shown that terpenoids undergo molecular arrangement during wine aging, and there is a transformation relationship between citronellol, geraniol, and linalool. This rearrangement is biased towards the production of linalool [27; 28]. Therefore, it is believed that this result is due to the chemical changes that occur during the winemaking, specifically the conversion of citronellol to geraniol and then to linalool. This conversion leads to a reduction in citronellol and an increase in linalool. The bottle storage is a period of wine ripening during which many chemical reactions occur. This study identified two trends in the evolution of aroma compounds during this stage. Firstly, the concentrations of aroma compounds increased during the first three months of bottle storage, and subsequently decreased. The phenomenon described in this text is similar to one observed by [PERSON] et al. [29]. They found that the concentrations of most esters, alcohols, and acids in the 'Cabernet Sauvignon' dry red wines increased during the first 3-9 months of the bottle storage, and then declined. The first evolutionary trend contained a large amount of linear long-chain fatty acid ethyl esters, such as ethyl nonanoate and ethyl heptanoate. The decrease in these esters led to a weakening of fruity and floral flavors in the wines [30]. Research has shown that the concentration of dissolved oxygen in wine during bottle storage is the highest at the beginning of bottle storage and then drops sharply within three months [31]. This process leads to the acid-catalyzedhydrolysis of fatty acid ethyl esters, resulting in the formation of acetic acid esters [31; 32]. This also explained the rapid decline in the concentrations of fatty acid ethyl esters in the initial stage of bottle storage, and the increase in concentrations of some acetic esters (isobutyl acetate, heptyl acetate, isoamyl acetate, etc.). Secondly, the concentration of aroma compounds continued to increase over time, with a majority of the included esters being short-chain fatty acid ethyl esters, such as ethyl 2-methylbutyrate, ethyl 3-methylbutyrate, and ethyl butyrate.