Pressing

Pressing (joso, 上槽) is the key step in sake production in which fully matured moromi (fermentation mash) is pressed to separate it into refined sake and sake lees (sake kasu). The step is also called shibori, and traditionally the moromi was packed into cloth sake bags and lined up in a fune (traditional press), where the sake was drawn off naturally by gravity. The basic flow of pressing is as follows. First, the moromi is packed into sake bags holding roughly 5 to 9 liters each, and the bags are lined up and stacked in the fune. The cloudy sake that runs out at this first stage is called Arabashiri. Once the fune is full of bags, a frame called a kasawaku is placed on top and more bags are stacked above it. The sake is then left to drip out naturally, usually for about 3 hours, in a stage called mizubune. Afterward, when the stacked bags have gradually settled, the kasawaku is removed, and further pressure is applied using a pressing lid (oshibuta) and wooden beams (makuragi). This stage is called oshibune. Once pressing has been carried out, the bags are rearranged the following day and pressed again (semebune). The sake taken out at this point is called seme, and the sake that flows out between the Arabashiri and this later stage is called nakadare. In recent years, automatic presses have become widespread, allowing sake to be pressed more efficiently. Traditional methods nonetheless remain firmly rooted, and pressing technique contributes greatly to the quality of the sake.