## Results
### Effect of Dealcoholization on Volatile Compounds
#### 3.2.1 Esters  
Many of the essential fruity aromas and flavors found in wine are imparted primarily by esters [70,71]. Esters also contribute greatly to the acid-ethyl ester balance, primarily through esterification and hydrolysis reactions during dealcoholization [50]. Consequently, the removal of ethanol from wine could affect the concentrations of esters (especially ethyl esters) and their respective acids, as the equilibrium simultaneously shifts towards ester hydrolysis Equations (1) and (2), with different equilibrium points forming for different esters [72]. esterification and hydrolysis are reversible reactions [57], with temperature and activation energy influencing the rate of each reaction [73]. Therefore, an optimal operating temperature during dealcoholization is crucial for the acid-ethyl ester equilibrium. \[\text{Carboxylic acid + Ethanol}\rightleftharpoons\text{Ester + Water} \tag{1}\]  
\[\text{RCOOH + C}_{2}\text{H}_{5}\text{OH}\rightleftharpoons\text{RCOCO}_{2} \text{H}_{5}+\text{H}_{2}\text{O} \tag{2}\]  
Regarding the identified esters, ethyl lexanoate, ethyl octanoate, and ethyl decanoate originate from fermentation, while diethyl succinate and ethyl lactate can be formed by chemical esterification during alcoholic fermentation and storage. The original wines had the highest total ester levels in terms of both number and concentration (ranging from 6536 \(\upmu\)g/L to 15,654 \(\upmu\)g/L), while the dealcoholized fractions had the lowest levels (Table 2). Esters are often hydrophobic, so losses were expected during the dealcoholization experiments, which varied depending on their physical and chemical properties. Dealcoholization by VD significantly reduced the total concentration of esters in white, rose, and red wines by 96%, 98% and 96%, respectively, compared to the original wines, while RO resulted in 92%, 81% and 87% losses, respectively. Specifically, dealcoholization by VD resulted in significant losses in the concentrations of phenethyl acetate (77-100%), ethyl 2-hexanoate (96-100%), ethyl acetate (91-100%), ethyl decanoate (99-100%), ethyl hexanoate (99-100%), ethyl 1-hexanoate (99-100%), ethyl 1-hexanoate (99-100%), ethyl 1-hexanoate (97-100%), and ethyl octanoate (99%) in dealcoholized wines compared to the original wines and, to a greater extent, complete losses (100%) of ethyl nonanoate, ethyl (Z) hex-3-enoate, ethyl butanoate, ethyl hexadecanoate, ethyl heptanoate, ethyl dodecanoate, and isoamyl octanoate in white or red wines (Table 2). This decrease in ester concentrations is consistent with other authors' reports of dealcoholized white wines [12,74] and red wines [16,19,51,55]. In contrast, significant losses of ethyl esters of hexanoic acid, octanoic acid, and decanoic acid were observed after dealcoholization with 5% \(v/v\) ethanol using membrane contactor technology, with losses of 75-88%, 47-80%, and 34-65%, respectively [13]. RO completely (100%) removed ethyl heptanoate, ethyl nonanoate, heptyl acetate, and methyl salicate from rose wine, while hexyl acetate was completely removed from red wine. However, the losses of esters such as ethyl hexadecanoate, ethyl acetate, hexyl acetate, and diethyl succinate were much lower in RO dealcoholized white wine fractions.