- (Synthetic) resin smell
A particular smell found in seishu which has been stored in tanks made of synthetic resins or plastics. Reminiscent of plastic, it has also sometimes been called “paper carton smell” (kami pakku-shu (long final “u”) 紙パック臭), but normal contemporary cartons are made of polyethylene, and it is thought they they do not impart any odour to the sake.
It is often more easily detected as flavour-in-the-mouth (hikikomi-ka) than in the top notes. The greater the movement of air through the vessel, the easier it is for other off-odours (besides the smell of the synthetic materials of the tanks itself) to be absorbed by the sake, so it is important to make the tank as airtight as possible.