## 3 Non-Thermal Technologies in Winemaking Process
### High Hydrostatic Pressure (HHP) Effects on Wine Phenolics, Color, and Aroma
[39], HHP was applied to limit the use of SO\({}_{2}\) in wine production. Red wines made with the addition of SO\({}_{2}\) (0-100 mg/L) were pressurized at 350 MPa for 10 min, and the impact on the wine's chemical composition was investigated during 12 months of storage. The results showed that HHP did not affect the chemical composition of wine right after processing. However, after 6 months, HHP-treated wines (\(<\)60 mg/L SO\({}_{2}\)) presented increased hue value and decreased concentration of monomeric anthocyanins and flavanols, as well as antioxidant activity. In addition, those wines were also characterized by scarce aromaticity, higher oxidation, and dried fruity notes compared to untreated wines. Nevertheless, after 12 months, no great difference was found in the chemical composition of pressurized wines containing over 60 mg/L SO\({}_{2}\) and unpressurized ones, suggesting that HHP could be used to complement the action mechanisms of SO\({}_{2}\). Recently, [PERSON] et al. [41] treated young red and white low-SO\({}_{2}\) wines (free SO\({}_{2}\) 25 mg/L for both) with different pressures (200-600 MPa) and treatment times (5-25 min) to evaluate the HHP effects on wine chemical composition. Aside from that, the authors investigated the combined effect of HHP (200 MPa for 5 min) and the addition of antioxidants (SO\({}_{2}\) and glutathione) during 12 months of aging. In general, HHP treatments led to a slight reduction in total and individual phenols in both wines immediately after processing, while an increase in some free phenolic acids (white wine) and color was observed. These changes were more conditioned by applied pressure than by treatment time. After 12 months, the pressurized red wines had a lower concentration of phenols, anthocyanins, and flavanols, while the color and aroma composition remained the same. In contrast, HHP affected the aroma composition of white wines after 12 months without major changes in most phenols and color. Finally, pressurized wines with standard SO\({}_{2}\) (free SO\({}_{2}\) 25 mg/L for rods; free SO\({}_{2}\) 45 mg/L for whites) and low SO\({}_{2}\) and glutathione (free SO\({}_{2}\) 10 mg/L + 20 mg/L GSH for rods; free SO\({}_{2}\) 25 mg/L + 20 mg/L GSH for whites) were very similar in aroma composition (red wine) and in phenolic and color composition (white wine). This aging experiment indicated that combining the addition of HHP and glutathione along with lower SO\({}_{2}\) doses  
Figure 5: High hydrostatic pressure (HHP) mechanism of microbial inactivation in wine. This Figure was published in Preservatives and preservation approaches in beverages, Vol 15, [PERSON] and [PERSON], Nonthermal preservation of wine, 203–235, Copyright Elsevier (2019) [75]. may be a promising approach for preserving wine. In addition, [PERSON] et al. [40] also combined HHP with the addition of glutathione and SO2. Red wine was firstly subjected to different HHP treatments (200-600 MPa, 0-15 min), after which optimal HHP parameters (400 MPa for 5 min) were selected based on acceptable changes in quality characteristics, precisely on the lower reduction in polyphenols, anthocyanins, and proanthocyanidins, and the lower increase in volatile acidity and acetic acid values. Then, red wines containing glutathione (10 mg/L) and SO2 (0-100 mg/L) were treated with selected HHP conditions. After 12 months of storage, HHP-treated wines were sensory characterized as \"mature\" with higher content of aldehydes and ketones, and lower content of phenols and esters. Furthermore, pressurized wines with intermediate content of SO2 (40 and 60 mg/L) were considered to be better in body, balance, and overall quality, followed by lower astringency and bitterness, suggesting that these SO2 doses in combination with HHP and glutathione could ensure adequate wine stability. [PERSON] et al. [38] reported that HHP (200 MPa for 15 and 25 min) had more beneficial effect on the reduction in _B.