## 3 Non-Thermal Technologies in Winemaking Process
### High-Power Ultrasound (HPU) Effects on Varietal Aroma/Phenol Extraction and Wine Quality
Furthermore, HPU (150 W, 30 \({}^{\circ}\)C, 30 min) was reported to be very efficient in reduction in higher alcohols in red wine, thus improving wine sensory characteristics [30]. The same authors also showed that this decrease was influenced by tartaric acid, ethanol concentration, mannitol, iron, and copper ions in the wine, which may be related to ultrasound-formed free radicals and their further reactions. Another study by [PERSON] et al. [34] also showed a reducing effect of HPU (59 kHz, 200 W, 30 \({}^{\circ}\)C, 30 min) on higher alcohols, as well as on phenolic compounds and color parameters, indicating the importance of selecting suitable ultrasound equipment (bath/probe) and conditions (frequency, power, time, temperature) during the processing of wine. [PERSON] et al. [27] studied the effect of HPU at various amplitudes (41 and 81%) and treatment times (1, 3, and 5 min) on the chemical composition of two young red wines and found no detrimental effect of HPU on anthocyanins and phenolic compounds, as well as chromatic characteristics with an increase in ultrasound parameters. However, higher amplitude (81%) induced greater reduction in tannins (15 and 40%) after wine storage (15 and 30 days). Recently, the effect of ultrasound amplitudes (30-90%) and treatment times (5-10 min) was also explored on the stability of proteins in two different Italian white wines [26]. The results demonstrated increased protein stability with an increase in ultrasound amplitude and treatment time, where HPU at 90% amplitude and 10 min achieved full stabilization effect on wines. Aside from that, HPU induced some positive changes in the conformational structure of wine proteins. [PERSON] and [PERSON] [28] used HPU at different amplitudes (30-90%) and treatment times (2, 6, and 10 min) to treat a young  
Figure 4: High-power ultrasound (HPU) mechanism of microbial inactivation in wine. T: temperature. This Figure was published in Preservatives and preservation approaches in beverages, Vol 15, [PERSON] and [PERSON]. [PERSON], Nonthermal preservation of wine, 203–235, Copyright Elsevier (2019) [75]. Cabernet Sauvignon red wine. The results demonstrated no degradative effect of increased HPU processing conditions on wine phenolic profile. However, HPU led to an increment in the polymerization of tannins and a reduction in the astringency index and particle size. Similarly, [PERSON] et al. [31] employed low-frequency ultrasound (24 kHz, 22 mm probe, 400 W, 100%, 3 min) to improve the taste quality of red wine, thus reducing tannins and astringency and increasing polyphenols and anthocyanins. Apart from improving wine organoleptic properties, HPU showed to be effective in increasing particle size distribution, viscosity coefficient, yield stress, and mass transfer in red wine [33]. On the other hand, [PERSON] et al. [29] applied HPU (24 kHz, 14 mm diameter probe, 125 \(\upmu\)m amplitude, 0.73 mL/s flow rate) to five different table wines and revealed that antioxidant activity and total phenols of most wines decreased after HPU processing, while color density slightly increased. However, HPU did not influence the quality characteristics of wine during 2 months of storage. In a study from [PERSON] et al. [20], a pilot-scale HPU system at two different frequencies (20 and 28 kHz) was applied during skin maceration (48 and 72 h) of Monastrell red grapes. Firstly, authors reported on morphological changes in grape cells induced by HPU processing. Secondly, HPU-treated grapes at 20 kHz showed a lower fermentation degree during the first period of fermentation, which was attributed to the HPU effect on the microbial population. After 72 h of maceration, the HPU-treated samples at 28 kHz presented the highest total phenol index, total anthocyanin content, and color intensity. However, at the end of fermentation and bottling, a 7-day macerated control sample showed the highest values of the abovementioned parameters, along with the content of polymeric anthocyanins and methyl cellulose precipitable tannins.