# Quality Characteristics and Antioxidant Activities of Six Types of Korean White Wine
## 3 Results and Discussion
### Total Phenolic and Flavonoid Contents in Korean White Wine  
Flavonoids and phenolic compounds, which are recognized as functional components in wine, are derived from grape seeds and skins [38]. During white wine production, grape skins are not utilized during the fermentation process. Due to the relatively lower anthocyanin content in white grape skins, white wines generally exhibit reduced levels of total phenolic and flavonoid compounds compared with red wines. However, these two compound categories remain valuable indicators for exploring differences in functional characteristics among diverse grape cultivars. Therefore, the levels of total phenolic compounds and flavonoids in white wines derived from six types of white grape cultivars were analyzed (Figure 2). The results revealed significantly higher levels of total phenolic and flavonoid compounds in the VB wine, whereas the other wines expectedly showed lower levels of these compounds. This disparity could be attributed to the presence of slightly more color pigments within the skin of VB grapes (Figure 1). This facilitates higher extraction of phenolic and flavonoid compounds during the juice extraction process compared with other grape cultivars. Phenolic compounds including flavonoids (e.g., anthocyanins, flavan-3-ols, and flavonoids) and nonflavonoids (e.g., phenolic acids and stilbenes) represent secondary metabolites found in grapes and wine. They assume a pivotal role as quality indicators in wine assessment [39]. Phenolic acids, including hydroxybenzoic acid and hydroxycinamic acid, are abundantly present in white wine. Their role as oxidative substrates and precursors contributes to the bitter taste inherent to white wine [40; 41]. These compounds play a crucial role in defining \begin{table}
\begin{tabular}{l c c c c c c} \hline
**Item** & **CB** & **SM** & **SB** & **KN** & **VB** & **CS** \\ \hline pH & 3.79 \(\pm\) 0.02 b & 3.59 \(\pm\) 0.01 d & 3.75 \(\pm\) 0.02 c & 3.84 \(\pm\) 0.03 a & 3.19 \(\pm\) 0.02 f & 3.40 \(\pm\) 0.03 e \\ Total acidity (g/L) & 8.0 \(\pm\) 0.0 a & 7.7 \(\pm\) 0.0 b & 6.3 \(\pm\) 0.0 d & 5.7 \(\pm\) 0.0 e & 6.6 \(\pm\) 0.0 c & 5.3 \(\pm\) 0.0 f \\ Soluble solid (\({}^{\circ}\)Bris) & 7.0 \(\pm\) 0.0 b & 7.0 \(\pm\) 0.1 b & 6.2 \(\pm\) 0.1 d & 7.0 \(\pm\) 0.0 b & 6.8 \(\pm\) 0.1 c & 7.2 \(\pm\) 0.1 a \\ Reducing sugar (\%) & 0.10 \(\pm\) 0.01 d & 0.30 \(\pm\) 0.02 b & 0.12 \(\pm\) 0.02 d & 0.53 \(\pm\) 0.02 a & 0.26 \(\pm\) 0.01 c & 0.11 \(\pm\) 0.01 d \\ Alcohol (\%) & 11.8 \(\pm\) 0.1 d & 2.2 \(\pm\) 0.1 c & 10.4 \(\pm\) 0 f & 12.4 \(\pm\) 0.1 b & 12.6 \(\pm\) 0.1 c & 10.6 \(\pm\) 0.0 e \\ Free sugar (mg/mL) & & & & & & & \\ Glucose & ND & ND & ND & 0.34 \(\pm\) 0.04 a & ND & 0.38 \(\pm\) 0.06 a \\ Galactose & 0.15 \(\pm\) 0.01 b & 0.17 \(\pm\) 0.02 ab & ND & ND & 0.21 \(\pm\) 0.02 a & 0.12 \(\pm\) 0.01 c \\ Fructose & 0.46 \(\pm\) 0.06 c & 0.78 \(\pm\) 0.08 b & 0.32 \(\pm\) 0.05 c & 1.03 \(\pm\) 0.12 a & 0.65 \(\pm\) 0.09 b & 0.40 \(\pm\) 0.06 c \\ Organic acid (mg/mL) & & & & & & & \\ Citric acid & 1.27 \(\pm\) 0.20 a & 1.17 \(\pm\) 0.13 a & 0.61 \(\pm\) 0.10 b & 0.42 \(\pm\) 0.06 b & 0.48 \(\pm\) 0.07 b & 0.46 \(\pm\) 0.04 b \\ Tartaric acid & 2.78 \(\pm\) 0.19 b & 2.81 \(\pm\) 0.23 b & 2.10 \(\pm\) 0.17 c & 1.58 \(\pm\) 0.21 d & 4.07 \(\pm\) 0.35 a & 3.09 \(\pm\) 0.24 b \\ Malic acid & 8.71 \(\pm\) 0.68 a & 7.68 \(\pm\) 0.82 a & 5.32 \(\pm\) 0.49 b & 4.93 \(\pm\) 0.58 b & 3.37 \(\pm\) 0.38 c & 2.95 \(\pm\) 0.41 c \\ Succinic acid & 2.22 \(\pm\) 0.16 a & 2.09 \(\pm\) 0.22 a & 0.99 \(\pm\) 0.13 c & 1.93 \(\pm\) 0.15 a & 1.37 \(\pm\) 0.16 b & 0.96 \(\pm\) 0.10 c \\ Acetie acid & 0.03 \(\pm\) 0.01 c & 0.17 \(\pm\) 0.02 a & 0.07 \(\pm\) 0.01 c & 0.12 \(\pm\) 0.03 b & 0.05 \(\pm\) 0.01 c & 0.04 \(\pm\) 0.01 c \\ \hline \end{tabular}
\end{table} 
Table 2: Physicochemical characteristics of Korean white wines produced using six types of white grape cultivars. Figure 2: Total phenolic and flavonoid contents in white wines produced using six types of white grapes cultivated in Korea.