## 3 Non-Thermal Technologies in Winemaking Process
### High-Power Ultrasound (HPU) Effects on Varietal Aroma/Phenol Extraction and Wine Quality
In addition, all HPU-treated samples showed a higher extraction of total tannins in all three stages of wine production (after maceration, complete fermentation, and at bottling). No remarkable changes were observed in volatile acidity, tartaric, and malic acids. Finally, the higher alcohol and tann content was observed in wines obtained from grapes treated by 20 kHz HPU, whereas higher anthocyanin content was achieved at 28 kHz. The same winery scale HPU system was also used to process Monastrell red grapes, favoring the extraction of grape phenolic compounds and allowing for the production of low-alcohol wines [19]. Moreover, HPU processing of red grapes at the same frequencies has been reported to increase free varietal aroma compounds (C6 alcohols, terpen, and norisoprenoids) in musts and wines [22]. More recently, [PERSON] et al. [17] conducted a study on the effect of HPU on the color and aroma of rose wines using a semi-industrial-scale system at 30 kHz, and found higher values of color intensity, total polyphenols, and anthocyanins in wines obtained from HPU-treated crushed grapes. The extraction of varietal aroma compounds in HPU musts was also enhanced, while finished HPU wines showed increased content of some norisoprenoids and terpen. From a sensory aspect, HPU resulted in wines with more intense fruity-flaval notes and aftertaste characteristics. Similarly, increased content of phenols and free thiols was observed after processing of Sauvignon Blanc white grape must with a HPU probe at 20 kHz and 153 \(\upmu\)m amplitude [23]. In addition, [PERSON] et al. [18] used a HPU probe device (20 kHz, 50-90%, 3-5 min) to treat crushed red Merlot grapes before maceration, and also observed increased the extraction rate of phenolic compounds and antioxidant activity. [PERSON] et al. [21] explored the effect of combined HPU and low temperature pretreatment on the quality parameters of Merlot dry red wine. In this study, low temperature, ultrasonic bath treatment (120, 240, and 400 W), and their combinations were applied to must before fermentation. The results demonstrated that HPU combined with low temperature pretreatment had a positive effect on the quality composition of produced wine, leading to an increase in the content of anthocyanins and phenolic acids, which additionally affected chromatic composition and improved antioxidant capacity. Furthermore, HPU of 240 W combined with low temperature pretreatment decreased unpleasant odors and enhanced fruity and floral aromas as well as the aftertaste of the wine. Recently, HPU bath treatment was applied during the fermentation process with the aim of enhancing the quality of fortified sweet red wine [32]. The study showed an increasing effect of ultrasound (200 W/20 min or 400 W/40 min) on total phenols, anthocyanins, and aroma compounds in fresh fortified wine, thereby improving sensory characteristics. In addition, a positive HPU effect was found on the color stability in aged fortified wines, along with no promoting effect on the increase in harmful ethyl carbamate. To conclude this section, the literature shows that ultrasound technology can be used at different stages of winemaking to improve the extraction of valuable bioactive compounds, prevent protein precipitation, minimize requirements for SO\({}_{2}\) and fining agents, reduce alcohol content, and improve wine quality and sensory characteristics. In addition, HPU is also considered the most successful technology for the microbial stabilization of wine, with varying degrees of effectiveness in inactivating yeasts and bacteria, and accelerating the aging process. A critical review paper was recently published by [PERSON] et al. [7], highlighting that studies are moving towards combining ultrasound with other physical and chemical treatments to reduce processing time and nutrient losses and achieve better inactivation results.