## 3 Non-Thermal Technologies in Winemaking Process
### High Hydrostatic Pressure (HHP) Effects on Wine Phenolics, Color, and Aroma  
High hydrostatic pressure is one of the most studied non-thermal processing technologies used to preserve or modify food. HHP broadly encompasses the application of pressure (between 100 and 800 MPa) to food placed in a chamber, with or without packaging [75]. In HHP processing, the pressure is applied uniformly and instantaneously to the food from all directions according to [PERSON]'s principle (Figure 5) [78]. Regarding winemaking, HHP showed great potential in several areas, resulting in a reduction in microorganisms and requirements for SO\({}_{2}\), as well as in accelerated aging and improved wine quality characteristics [10]. In addition to that, HHP has proven to be excellent in enhancing the extraction of phenolic compounds into the must/wine by affecting the integrity of membranes and cell walls at higher pressures [79; 80]. The latest HHP applications and their effects on wine are outlined in Table 3.  
[PERSON] et al. [36] examined the effect of HHP (500 MPa for 5 min) on the phenolic composition of red wine and compared it to the conventional wine aging methods ( oak barrels, oak chips, and microoxygenation with oak chips). The results revealed that HHP affected wine phenolic composition, reducing monomeric anthocyanins, phenolic acids, and flavonoids. Moreover, HHP treatment did not cause major modifications in the taste and color of wines. However, wines treated with HHP and those treated with microoxygenation and oak chips were characterized by a similar rate of tannin polymerization, pyranoanthocyanins, and percentage of prodelphinidins, indicating that HHP can lead to the production of wines with more aged-like characteristics. Recently, [PERSON] et al. [37] found that HHP treatments (400 MPa for 5 and 30 min) in combination with holm oak chips could produce wines with physicochemical and sensory characteristics similar to those from oak chips during classic maceration in tanks for 45 days. The impact of acceler \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Sample** & **Processing Conditions** & \multicolumn{1}{c}{**Key Outcomes**} & **References** \\ \hline Monastrell red grapes & Semi-industrial-scale ultrasonic system (30 kHz frequency; 2500 W power; 8 W/cm\({}^{2}\) power density) & \(\bullet\) & Increase in color intensity and phenolics. Enhanced extraction of varietal volatile compounds in musts. Increased content of certain aroma compounds in wines. Improved sensory characteristics of wines. & [17] \\ \hline Merlot red grape must & Ultrasonic bath (120, 240, 400 W; 30 min) combined with low temperature pretreatment (4 \({}^{\circ}\)C/12 h) & \(\bullet\) & Increase in phenolics. Increased antioxidant capacity. Significant change in color. Improved aroma and aftertaste. & [21] \\ \hline Merlot red grapes & Ultrasonic probe (diameter 13 mm; 20 kHz frequency; 50, 70, 90\% amplitude; 3, 4, 5 min) & \(\bullet\) & Increased extraction of phenolic compounds. Increased antioxidant activity. & [18] \\ \hline Cabernet Sauvignon fortified sweet red wine & Ultrasonic bath (20 kHz; 200, 300, 400 W; 20, 40, 80 min) & \(\bullet\) & Increased content of phenolic and aroma compounds. Reduced degradation of anthocyanins. Improved color stability and sensory characteristics. Decreased content of ethyl carbamate after aging. & [32] \\ \hline Sauvignon Blanc white grape must & Ultrasonic probe (diameter 13 mm; 20 kHz; 3 and 5 min; 153 μm amplitude; 200 W & \(\bullet\) & Increase in phenols and conductivity. Increased extraction of free thiols. & [23] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._ated aging was observed in the white wine variety, while in the red Tempranillo variety, only minor sensory changes occurred, indicating the importance of the optimization of HHP processing conditions (pressure and holding time) for each wine variety, along with differences in the concentration and composition of wood chips. In a study by [PERSON] et al.