koji-buta (wooden tray) method

The futa-koji method (蓋麹法) is a traditional koji-making technique in which koji is grown on koji-buta, small wooden trays. Known as a conventional method of koji production, it is particularly well suited to brewing ginjo sake because it improves the saccharification efficiency of the koji. Managing the koji this way takes considerable effort, but it makes it easier to guide the koji toward the intended quality. Because it demands precise control, the method is widely used especially when brewing high-quality sake.