# Helium Atmospheric Pressure Plasma Jet Source Treatment of White Grapes Juice for Winemaking
## 2 Materials and Methods
### Methods for Characterization of Must and Wine
#### 2.2.2 The Colour of the Wine and Its Colour Space Parameters (CIELab)  
Wine is a product that can be described nowadays both as a commodity but also as a luxury, depending on its marketing price. Moreover, wine is a complex mixture of water and ethanol (as major components), and glycerol, aliphatic and aromatic alcohols, phenols, sugar, salt or organic acids (as minor components). That being said, the concentration of these minor components is of great importance for the quality and preferences classification from the industry and consumers point of view. Nonetheless, the color of wine is one of the first parameters evaluated by consumers and contributes, as well, to the wine's quality perception and acceptance. The color is mainly due to the phenols in the wine [82]. More, even the tasting of these beverages is strongly influenced by wine color, in the detriment of other sensorial parameters (temperature, aroma). Furthermore, the study of wine color is a must, bearing in mind that it is relative easy to be done. Nevertheless, many techniques are being used, even if some standardized methods are accepted by the OIV. Through colorimetry we have the possibility to define every color as a combination of three values, mainly known as color coordinates. Moreover, in the fields of enology the determination of the color spaces of liquid samples is of great importance, therefore being widely applied. For example, researchers evaluate color using the CIE \(L^{*}a^{*}b^{*}\) model of organic dyes and colorants and pH indicators, and enologists analyze the color of beverages (wine and spirit) samples. \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline
**Wavenumber Regions (cm\({}^{-1}\))** & **Groups** & **Assignment** \\ \hline \hline \(<\)1000 & stretching and bending vibrations & phosphates, phenolics, mono-substituted phenyl derivates, unsaturated lipids, carotenoids \\
1068–1065 1107–1110 1200 & stretching vibration of C-O O-H stretch second overtones & sugars and organic acids \\
950–1250 1457–1288 1530–1600 1516–1519 1610–1614 1700 & stretching and bending vibrations & hydrolyzable and condensed tannins glucose, oligo- and polysaccharides, alcohols aldehydes, carboxy amino acids and derivatives compounds, flavonoids organic acids \\
1704–1712 1600–1900 1600–2300 12100–2300 12800–3000 & C=O, C=C, -CH2-, C-H, -CH3, O-H C-N \\
2800–3000 2800–3000 & C=O, C=C, -CH2-, C-H, -CH3, O-H C-N \\ \hline \end{tabular}
\end{table} 
Table 1: Characteristic wavenumbers (cm\({}^{-1}\)) for bending vibrations and stretching in wine samples, as reported by [67; 68; 69; 72; 76; 77]The color is one of the most fundamental descriptors of wine, an attribute to which viticulturists and wine producers offer all their attention for growing grapes and winemaking. Due to different people's visual perception of wine color during tasting or organoleptic examination, a measurement of color was proposed by the Commission Internationale de l'Eclairage (CIE) and the OIV described the procedure as the one which offer the largest amount of information [83]. The CIE defines 3D graphs of all colors that humans can see, as a Cartesian coordinate system defined by three colorimeter coordinates \(L^{*}\) (lightness, from 0 -black to 100-white), \(a^{*}\) (redness/greenness, positive values for reddish and negative for greenish) and \(b^{*}\) (yellowness/blueness, positive for yellowish and negative for bluish) [83; 84; 85; 86], along parameters as chroma (\(C^{*}_{ab}\)), angular hue or tone (\(H^{*}\)), color intensity (C.I. ), hue, color difference (\(\Delta E^{*}_{ab}\)) and whiteness index (WI). Furthermore, chroma is the quantitative characteristic of colorfulness that enables the characterization of differences in the grey color between samples with the same lightness for each hue. Moreover, hue is regarded as the qualitative attribute of color, being the parameter from which colors are traditionally defined, e.g., blueish, pinkish, reddish or yellowish.