## 3 Results
### The Effect of High-Hydrostatic-Pressure Treatment on Volatile Aromatic Compounds
#### 3.2.2 The Impact of High-Hydrostatic-Pressure Treatment on Major Volatile  
The OAV serves as a metric for assessing the contribution of individual aroma compounds to the overall aroma of wine; an OAV value greater than 1 indicates that the aroma of the compound can be perceived by humans [18]. This study (Table 2) analyzed 19 sets of wine samples treated with different levels of HHP and found that the concentrations of 17 volatile aroma compounds, primarily esters, phenols, and alcohols, exceeded their sensory activity thresholds (OAV > 1). To further explore the effect of HHP treatment on these volatile compounds, we analyzed compounds with an OAV > 1 relative to the pressure and time dimensions. As shown in Figure 5, the content of each volatile substance in the three sample groups increased with pressure. Specifically, when the treatment times were 10 min and 20 min, the content of volatile substances reached peak values of 81.99 mg/L and 103.88 mg/L, respectively, when the pressure increased to 300 MPa. However, when the treatment time was extended to 30 min and the pressure was increased to 500 MPa, the volatile compound content reached its highest value (76.02 mg/L). However, upon further increasing the pressure to 600 MPa, the content of volatile compounds in all three sample groups decreased compared to their respective peak values by 9.21%, 46.89%, and 23.23%, respectively. Notably, ester compounds, which are typical byproducts of ethanol fermentation, significantly contribute to the floral and fruity aromas of wine. When the treatment pressure was set to 100 and 200 MPa, the contents of ester compounds, such as isoamyl acetate, ethyl acetate, and ethyl caprylate, in the three sample groups did not change significantly. However, as the pressure increased to 300 MPa, the ester content  
Figure 4: Distribution histogram of aroma substance content in wine samples treated with different HHP processes: (**a**) changes in volatile aroma substances under different HHP treatments; (**b**) changes in ester-type volatile aroma substances under different HHP treatments. rapidly increased to its maximum value. However, excessively high pressures could affect the stability of ester compounds, leading to a reduction in their content. The findings of this study echo the results of previous research, such as those reported by [PERSON] [21] in their wine studies. It has been reported that an increase in pressure causes changes in the volume of the treatment system, which may alter the chemical bond structure within the substance, thereby accelerating the chemical reaction rate of volatile substances and ultimately causing changes in the content of volatile substances. However, when the pressure is increased to a certain threshold, the reverse effect may occur [22]. An appropriate extension of the HHP treatment time also contributed to the release of volatile compounds from Marselan wine (Figure 6). Under different HHP conditions, the ester compounds in the six sample treatment groups increased by 14.28 mg/L to 43.73 mg/L compared to the control group. In particular, at pressures of 100 and 200 MPa, the ester content showed an increasing trend with the extension of the treatment time. However, when the pressure increased to 300 MPa, the ester content initially increased and then decreased (peaking at 20 min). Upon further increasing the pressure to 400 MPa, the change in ester compounds was no longer significant and showed a downward trend. The synthesis of ester compounds consumes a certain amount of chemical energy, and HHP treatment promotes this process by increasing the energy in the wine body [23]. At shorter treatment times, the chemical energy accumulated in the wine may not have been sufficient, possibly not reaching the activation energy required to induce ester-compound synthesis. When the treatment time reached 20 min, the chemical energy accumulated in the wine exceeded the energy required for the synthesis of ester compounds, leading to a significant increase in total ester content.