# Quality Characteristics and Antioxidant Activities of Six Types of Korean White Wine
## 3 Results and Discussion
### Volatile Aromatic Compounds in Korean White Wines
Although notable variations were observed in the concentrations of other higher alcohols across different wines, the total content of higher alcohols was largely determined by isoamyl alcohol and 2-phenylethanol. These two compounds were also detected in high levels in white wines prepared using autochthonous grape cultivars, Kristac and Zizak [57]. The total content of higher alcohols in the CB, VB, and CS wines was comparable, but the SB wine showed the lowest levels. Esters are known to considerably influence wine aroma. In this study, several esters, including ethyl acetate, isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl 9-decenoate, and 2-phenylethyl acetate, were detected in significantly higher concentrations than other ester compounds across all wines. These compounds strongly influence the aroma of white wine. The concentrations of these ester compounds directly contributed to the total ester content, which was remarkably higher in CB, SB, and CS wines than in the other wines, whereas the SM wine showed the lowest total ester content. Further, significant variations were observed in the concentrations of isobutyl acetate and hexyl acetate among the different grape cultivars. Interestingly, 2-phenylethyl acetate, despite originating from its precursor, 2-phenylethanol, which was present in higher amounts in the SM and KN wines, exhibited lower concentrations in these wines. This phenomenon can be attributed to the enzymatic activity of alcohol acetyltransferase during fermentation, a finding consistent with previous research [58]. A study conducted by [PERSON] et al. (2016) focused on the volatile compounds present in white wines produced from the grape cultivars Cheongsoo, Chardonnay, and Riesling cultivated in Korea. That study reported that the Cheongsoo wine exhibited a total ester content that was more than four times higher than that of Chardonnay and Riesling wines. Notably, the concentrations of compounds such as ethyl acetate, isoamyl acetate, hexyl acetate, ethyl hexanoate, ethyl octanoate, and ethyl decanoate were prominently elevated in the Cheongsoo wine compared to the other two cultivars [19]. Different groups of volatile aromatic compounds exist in wine at varying concentrations, and their impact on the sensory characteristics of wine can differ based on their odor thresholds [59; 60]. Monoterpene compounds for instance, are well known for imparting floral characteristics to wine and are commonly found in various white grape cultivars such as Muscat, Gewurtztramminer, Riesling, Sylaner, Traminer, Huxel, and Muller Thurugau [61]. These compounds possess low odor thresholds (100-400 ppb), making even minor concentration changes influential in shaping the aroma profile of the wine [32; 62]. In the present study, the relative proportions of monoterpene compounds in the wines produced from different grape cultivars exhibited the most significant variation compared to other groups of volatile aromatic compounds. Notably, the wine produced from the CS grape showed a higher diversity of monoterpene compounds, with the detection of eight different types, surpassing the other wines. In particular, the CS wine displayed substantial levels of 4-terpineol and p- cynene, along with significantly higher levels of \(\upbeta\)-citronellol and geraniol than the other wines. Interestingly, linalool, a compound commonly found in various white wines, was detected in exceptionally high levels in the KN wine when compared to the other wines. The total content of monoterpene compounds in the CS wine was 1.4-10 times higher than that in the other wines, underscoring the significant influence of the monoterpene-based floral aromatic profile on the sensory attributes of the CS wine in comparison to the other wines. PCA was conducted on the volatile ester and monoterpene compounds, which have a substantial impact on wine aroma, in order to compare the relationships between different wine cultivars and their respective groups based on variable loadings and PC scores (Figure 4).