Comparison of Compositions of Fractionated Grape Juice Prepared from Koshu and Chardonnay Grapes by Traditional Pressing Method

Abstract

　In this study, we investigated the differences in the composition of fractionated juice prepared from Koshu grapes, a Japanese grape species, as well as Chardonnay grapes by the traditional pressing method. In the case of Chardonnay grapes, it was found that the Cuvée (first pressing juice) possessed higher titratable acidity and a lower pH than the Taille (second pressing juice), similar to the findings in champagne production. The lower acidity and higher pH of the Taille of the Chardonnay grapes, compared to that of the Cuvée, were attributed to its lower organic acid content and higher potassium content. The tendency of titratable acidity between the Cuvée and the Taille of the Chardonnay grapes was not remarkably affected by the vintage. Additionally, it was found that late harvesting tended to reduce acidity and increase potassium content and pH. In contrast, the acidity of the Taille of the Koshu grapes was observed to be higher than that of the Cuvée, especially when prepared with early-harvested grapes. In addition, although the organic acid content of the Taille of the Koshu grapes was higher that of the Cuvée, it was found that its pH tended to be higher as well. The higher acidity of the Taille of the Koshu grapes, compared to that of the Cuvée, was attributed to its higher organic acid content. The high pH of the Taille of the Koshu grapes, which was observed to be equal to or greater than that of the Cuvée, was ascribed to its high potassium content. Additionally, the difference in the acidity of the Cuvée and the Taille reduced with later harvest dates. From the above-mentioned findings, it was concluded that in the production of sparkling wine from Chardonnay grapes, it is possible to fractionate the grape juice based on the methodology of champagne production. On the other hand, with respect to Koshu grapes, it was found that the tendency of titratable acidity of the Cuvée and the Taille was different, with the titratable acidity depending on the harvest time. Therefore, in the production of sparkling wine from Koshu grapes, it is important to determine the optimum harvest time, in addition to the appropriate handling and blending methods for the Cuvée and the Taille.