# Non-Thermal and Thermal Physical Procedures--Optimistic Solutions in the Winemaking Industry
## 2 The Use of Non-Thermal Techniques in Winemaking Optimization  
### Ultrasound Technique  
Low-intensity ultrasounds (<1 W) are commonly used to assess the physicochemical quality of food and beverages, while high-intensity treatments are applied to induce changes in their physical, microbial, and chemical attributes [19]. One major focus of the existing papers is the potential use of ultrasound technology in the aging process of wine, highlighting its effectiveness in modifying the chromatic characteristics and phenolic properties of wines [20]. In Figure 4, the frequently used keywords regarding the application of ultrasounds in wine quality are highlighted. Ultrasounds have been shown to induce chemical and structural changes similar to those occurring during natural aging, thus reducing aging time [21]. [PERSON] & [PERSON] [22] highlighted that an increase in amplitude (30%, 60%, and 90%) and sonication time (2, 6, and 10 min) did not affect the initial polyphenol profile of red wines, but an increase in the polymerization of tannins was induced, accompanied by a significant reduction in astringency perception, likely attributed to structural alterations in proanthocyanidins (by acoustic cavitation). This treatment has been effective for the microbial quality and safety of wine samples analyzed by [PERSON] et al. [19], the results being dependent on different variables like time and waves intensity, but also on the microorganism's species and strain. _Brettanomyces_ spp. was more sensitive on ultrasounds than other species, while _Lactiplantiobacillus plantarum_ was the more resistant. It seems that ultrasound waves manifest variable effects on yeast vitality and viability. An important impact of ultrasound maceration on the physicochemical characteristics of wine was presented by our team [23]. A lower acidity was obtained in Busuioca de Bohotin samples treated with ultrasounds, compared with other maceration procedures like cryomaceration, microwave maceration, thermomaceration, or classical method. The authors highlighted that the chemical composition of the grapes (strongly related to the climate variables) is more important in the effectiveness of different maceration techniques, while in different years they obtained contrary results regarding the total polyphenol content. The samples obtained with ultrasounds were generally less colored [23]. Figure 4: Co-occurrence of the keywords found in the existing research on the use of ultrasounds in winemaking. The size of node signifies the number of occurrences, while the distance of the linking lines characterizes the relation between two nodes. The color of the items indicates the cluster to which they belong. Ultrasound treatment during maceration involves the production of micro bubbles due to the action of ultrasonic cavitation, and their breakdown produces several physical and thermal changes, which will ultimately accelerate the transfer of compounds from the solid parts of the fruit into the must. The results are influenced by ultrasound frequency, power, amplitude, and applied temperature. [PERSON] et al. [24] studied the ultrasound-assisted extraction of organic acids from grapes and wine by-products using ultrasonic probes at 200 W, 24 kHz, amplitudes from 30 to 90%, and treatment times from 2 to 25 min. The authors aimed to recover acids from wine by-products, and they obtained higher concentrations of tartaric and malic acids in the analyzed samples when they applied the ultrasound treatment. [PERSON] et al. [25] presented a significant improvement in the extraction rate of polyphenols in the by-products resulting from the wine industry when using ultrasound (400 W, 90% amplitude, 25 min extraction time). Also, [PERSON] et al. [26] confirmed that ultrasound maceration treatment generates an enriched volatile profile, as well as higher concentrations of tannins, in a much shorter time.