# Quality Characteristics and Antioxidant Activities of Six Types of Korean White Wine
## 3 Results and Discussion  
### Physicochemical Characteristics of Grape Must and Wine  
In this study, the physicochemical characteristics of six types of white grape cultivars, including one domestic (Cheongsoo) and five international cultivars were analyzed (Table 1). Among these, the KN grape displayed the highest pH, whereas the VB grape showed the lowest pH; the other cultivars exhibited minor variations. Total acidity was the highest in the CB grape and the lowest in the KN grape; further, despite its low pH, the total acidity of the VB grape was not considerably high. All grape cultivars exhibited a high soluble solid content of \(\geq\)18\({}^{\circ}\)Brix, with the CB, SM, KN, and VB cultivars showing a higher sugar content (20\({}^{\circ}\)Brix) than that in the typical Korean grape cultivar Campbell Early (approximately 14\({}^{\circ}\)Brix). The contents of both reducing sugar and free sugar, including glucose and fructose, were notably elevated, similar to the trend observed in soluble solids, indicating that all grape cultivars had sufficient sugar content for winemaking,thereby avoiding chaptalization. Regarding the organic acid content, the VB cultivar, which displayed the lowest pH, exhibited significantly higher tartaric acid content than other cultivars. Additionally, the CB, SM, and SB cultivars showed higher citric acid levels than other cultivars. The malic acid content was the highest in the CB cultivar, whereas the KN, VB, and CS cultivars exhibited relatively lower levels. The six types of white grape cultivars were subjected to fermentation at 15 \({}^{\circ}\)C, and their physicochemical characteristics were subsequently analyzed (Table 2). The VB wine, boasting the lowest initial pH among the grape cultivars, exhibited a further pH decrease to 3.19 after fermentation. Conversely, the KN wine, with the highest initial pH, also exhibited a pH decrease post-fermentation, aligning its pH with that of the CB and SB wines. The pH values of the SM and CS wines also exhibited slight reductions after fermentation. The total acidity of all the wines increased after fermentation, which was attributed to organic acid production during yeast metabolism throughout the fermentation process. Soluble solid content across the wines ranged from 6.2\({}^{\circ}\)Brix to 7.2\({}^{\circ}\)Brix, and all the wines exhibited reducing sugar levels below 1%, confirming the successful completion of fermentation. Regarding alcohol content, the CB, SM, KN, and VB wines, initially featuring sugar content of \(>\)20\({}^{\circ}\)Brix, exhibited alcohol levels of 11.8-12.6%, typical for wines. The SB and CS wines exhibited slightly lower alcohol content at 10.4% and 10.6%, respectively. Analysis of free sugar content indicated significant consumption of glucose and fructose, similar to the results from the reducing sugar content analysis. Concerning organic acid content, citric acid levels significantly increased in the CB and SM wines, while showing slight increments in the other wines. Moreover, tartaric acid content significantly increased in all the wines except for the KN wine, while the malic acid content remained relatively stable across all the wines. Incremental changes were observed in succinic and acetic acid contents across all the wines compared to their grape counterparts. pH and total acidity are considered important factors that affect various sensory qualities of wine. They are influenced by the balance between the anionic forms of organic acids (primarily tartaric and malic acids) and major positive ions, primarily K [34]. Organic acids commonly derived from natural grapes include malic acid, citric acid, and tartaric acid; these grapes also contain short-chain organic acids such as succinic acid, acetic acid, and lactic acid, which are formed during various fermentation processes [35]. These organic acids considerably affect the perceived acidity, a crucial factor determining organoleptic quality. Additionally, short-chain organic acids can act as secondary supporters for iron absorption [35; 36].