Filtration smell

A collective name for various odours which can be transferred to seishu from the materials used when sake is filtered.They include  kami-shu (long “u” for shu, smell), paper smell), caused when filtration paper is used, momen-shu (cotton smell), from cotton materials insufficiently washed,  fukuro-ka from unhygienic saka-bukuro, and tanso-shu (charcoal smell) from active carbon. This last is a burnt smell, somewhat similar to varnish or paints. The following are thought to be the reasons for its occurrence.

  1. Large quantities of carbon are used.
  2. The carbon used was left for a long time after opening and adsorbed unwanted substances.
  3. The carbon was left in contact with the sake for a long time.

Carbon smell is relatively difficult to detect with the nose alone, but becomes radically more noticeable in the mouth, and has a considerable effect on taste. Usually, it has the effect of masking the pleasant aroma of the sake proper.