Sake is often called 'rice wine,' but scientifically, its production process is much closer to beer. While wine is made by fermenting the natural sugars in fruit, sake is made by converting the starch in rice into sugar and then into alcohol. This is a two-step process called 'multiple parallel fermentation.' The key ingredient is 'Koji' (*Aspergillus oryzae*), a mold that is sprinkled onto steamed rice to break down the starches. The quality of sake is largely determined by how much the rice is 'polished' or milled. Polishing removes the outer layers of the rice grain (which contain fats and proteins that can cause off-flavors), leaving behind the pure starch core. The more the rice is polished, the more refined and expensive the resulting sake (such as Daiginjo) will be.