Nov. 24, 2016

SUNTORY TOMI NO OKA WINERY "From the Site of Viticulture"―Koshu Grapes from the Suntory Vineyard

Koshu, the grapes from the TOMI NO OKA WINERY vineyard, are picked late and are characterized by a full, ripe aroma and a flavor with a rich fruity component. After harvesting, the grapes are pressed to extract their juice, which is then fermented to make wine. The Koshu grapes, however, are pressed in bunches without destemming. The stem that links each individual grape to form the bunch is called the “peduncle.” Usually when making white wine, the peduncle is removed and just the grapes themselves are pressed to extract the juice. The Koshu grapes from Suntory’s vineyard are pressed in bunches without removing the peduncle, which creates a beautifully pure juice.

Pre-fermentation freeze concentration—A complex and round taste and rich fruity sensation

While some of the pressed juice is fermented as it is in a stainless steel tank, part of the juice is freeze-concentrated in a separate stainless steel tank prior to fermentation. Freezing fluid at -3°C is passed around the outside of the stainless steel tank to cool the juice, whereupon the pure water in the juice gradually turns into ice crystals and forms a layer of ice on the surface of the tank. As a result, the extracted component of the remaining juice is concentrated.

Juice that has been standing at subzero temperatures for around a month is beautifully clear and sparkles with a golden hue when poured into a glass, having a strong syrupy texture. When held in the mouth it presents a complex and round taste and rich fruity sensation, with a voluminous sensation that evokes the impression of plums, apricots, and other fleshy fruits.

Barrel fermentation—Drawing out the virtues of Tomi No Oka Koshu grapes

The freeze-concentrated juice is moved to a separate tank and its temperature gradually increased, after which it is barrel-fermented to give it a more complex flavor. The key here is to not use a new barrel. This is to bring to life the distinctive characteristics of the Koshu grapes from Suntory’s vineyard without excessively conferring the components or flavors of the barrel to the wine. In addition, we use several yeasts in the fermentation and evaluate their quality. What influence does the yeast have on the quality of the wine? Does it draw out the virtues of Tomi No Oka Koshu grapes? Through evaluating each one and pursuit of quality, we aim to further improve the taste of our wine.
Finally, through an assemblage (blend) of this barrel-fermented, barrel-matured Suntory vineyard Koshu wine with our Koshu wine fermented and matured in tanks, we finish the flavor of Tomi No Oka Koshu.

Japanese wine, and Koshu in particular, is currently attracting extremely enthusiastic attention on the wine market. To meet these expectations, all of the staff at the TOMI NO OKA WINERY are working together in pursuit of an even more delicious Koshu wine through repeated trials and errors.

“Tomi No Oka Koshu” 100% Suntory vineyard grapes