Kasu buai (sake lees yield ratio)

Kasu buai (sake lees yield ratio) is the weight of sake lees (sake kasu) produced, expressed as a percentage of the weight of the polished rice used as the raw material. When the moromi (fermentation mash) is pressed during production, sake lees is produced together with the sake. A high kasu buai means that more lees remains and, conversely, that less sake is obtained. A high kasu buai is generally associated with a luxurious sake, since a large amount of lees is produced from the rice. However, if the ratio is too high, production efficiency worsens and the quality of the sake can also be affected. On the other hand, a low kasu buai improves production efficiency, but it increases the risk of lower sake quality, so balance is important. The ideal kasu buai is set at the point that satisfies both the quality and the quantity of the sake.