- Mould smell, TCA smell
A mouldy smell like that found in corked wine. Derives from 2,4,6-trichloroanisole (TCA), and tends to be a particular problem with ginjo and sake which is filtered using only small quantities of active carbon.
TCA results from the metabolization of pentachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP, both used in wood preservatives) by moulds. Since this includes koji -kin, care is needed when handling wooden tools and equipment during brewing.
Measured with gas chromatography, it occurs in seishu at concentrations from 0-280 ng/L, and its discrimination threshold is held to be 0.75 ng/L .