Formalin

Formalin is a colorless liquid containing mainly formaldehyde at about 40%, with a distinctive pungent odor. In sake production, it is sometimes used as a disinfectant in the koji room (koji-muro, the room where koji is made). It is also used in measuring the amino acid level, where it contributes to quality control in brewing. However, formalin is a substance that must be handled with care, and because of its effects on health, cautious use is required.