Reionki (Cold temperature device)

A reionki is a tool used in sake brewing to cool the shubo (yeast starter) and moromi (fermentation mash). It is generally an elongated cylinder made of aluminum or stainless steel, and it is cooled by packing ice inside. Temperature control is critical in brewing, and the reionki is used to regulate the progress of fermentation and to prevent the growth of unwanted bacteria. Using it helps produce better-quality sake.