Kigayoshu (Wood scent)

Kigayoshu (木香様臭) is a type of aroma that arises under certain conditions during sake brewing. It is attributed mainly to aldehydes produced while yeast is fermenting, and it appears in particular when alcohol is added while the moromi (fermentation mash) is actively fermenting. The name comes from the fact that the aroma that emerges after pressing resembles kiga (wood aroma), although it is distinct from ordinary kiga. Its main component is said to be acetaldehyde, and it is also called aldehyde odor, but care is needed not to confuse it with ordinary kiga. Kigayoshu is sometimes treated as an off-odor and may affect the quality of the sake.