To make sake, brewers ferment rice in water. At the end of fermentation, at the conclusion of brewing, the tank contains a liquid element, sake, and a solid element: a "cloud" made of tiny soaked fragments of brewing rice.
In most cases, brewers carefully separate these two elements using cloth bags or presses. But not in the case of "nigori" or "cloudy" sakes. These batches contain a more or less significant portion of their brewing rice, which gives them a cloudy appearance, but also a dense texture and an unmistakable lactic aroma.