## 3 Non-Thermal Technologies in Winemaking Process
### Other Non-Thermal Technologies in Winemaking Process
#### 3.4.2 Cold Plasma (CP) Effects on Wine Phenolics and Color Characteristics  
Non-thermal plasma, commonly called cold plasma (CP), is an emerging non-thermal technology which has been increasingly investigated in recent years. By definition, plasma can be described as a fully or partially ionized gas with specific electrical, chemical, and physical characteristics that accompany the electromechanical principle of generating electric energy at ambient atmospheric pressure [88]. There are different approaches that can be employed to generate CP, and each of these plasma systems has a wide range of uses. Some of the most often used plasma systems in food processing include dielectric barrier discharge, corona discharge, pulse discharge, high-frequency discharge, microwave discharge, and glow discharge [89]. Recently, [PERSON] [16] summarized the latest trends in cold plasma processing of fruit beverages. In this review article, the author emphasized the great potential of CP for inactivation of different types of spoilage microorganisms and various endogenous enzymes while maintaining the quality characteristics of fruit beverages. The shown capabilities of CP on safety and quality control in the beverage industry also offered an opportunity to introduce this technology in the processing of wine. One of the potential applications of this technology in wine, more precisely the high voltage electrical discharge plasma, is shown in Figure 8.  
Figure 8: High voltage electrical discharge plasma treatment of wine. For example, [PERSON] et al. [68] studied the impact of atmospheric pressure cold plasma (APCP) on Tempranillo red wine quality in batch and flow systems. The results showed that argon APCP batch treatments (60 and 90 W at 1, 3, 5, and 10 min) provided wines with lower tonality, higher color intensity, total polyphenols, and anthocyanins. Moreover, the batch treatment with lower power had the most favorable effect. Contrary, continuous flow treatments (1.2 and 2.4. L/min, 60, and 90 W at 25 min) did not result in remarkable improvement of chromatic and phenolic characteristics, nor in the wine spoilage. Another study by [PERSON] et al. [67] also investigated the effects of CP treatments (60, 90, and 120 Hz at 3, 5, and 10 min) on the phenolic and chromatic composition of red Cabernet Sauvignon and white Grasevina wines. Researchers observed that CP affected the phenolic compounds stability in both wines while retaining the color. Among plasma parameters, treatment duration was highlighted as having the most influence. Indeed, the results showed a decrease in total phenolics, anthocyanins, and tannins, while most phenolic acids and flaxan-3-ols were slightly increased in white wine, allowing for better oxidative stability. The authors assumed that these various plasma effects were related to the structural diversity of phenolic compounds and consequently different antioxidant properties. Furthermore, [PERSON] et al. [66] explored white must treated with helium atmospheric pressure plasma jet (He-appj) system (16 kV, 0.8-0.9 mA, 48 kHz, 7-8 W, 200-300 W/cm\({}^{2}\), 4.6-6.6 mJ/cm\({}^{2}\)), and observed that selected process conditions provided a cold treatment (max. 40 \({}^{\circ}\)C) of must samples as well as a higher quantity of plasma reactive species which supported further oxidation processes. Authors also conducted the characterization of 1- and 2-year-old wines and the correlation of processing parameters (voltage, power, gas temperature, reactive species) with the physicochemical characteristics (pH, Brix, UV-Vis, and FTIR spectroscopy, CIELab and RGB color components) of white must and wine, and supported the possibility of using CP for wine production. Another application of APCP technology with different powers (90 and 500 W) and gasses (air, nitrogen, and argon) was demonstrated for the sanitization of the surface of oak wine barrels [71]. The authors observed complete inactivation of _B.