“Old stink”

An unpleasant odour reminiscent of Japanese pickles (tsukemono), occurring during storage, or in the final product after bottling. It is produced when amino acids and their metabolic products decompose. It is thought to consist mainly of polysulphides (dimethyl trisulphide (DMTS) and such) and isovaleraldehyde . It develops most dramatically in sake with a high amino-acid content or in that which is stored at high temperatures.

In nama-zake, isovaleraldehyde is produced by the enzymatic oxidization of isoamyl alcohol, but, in pasteurized sake in storage, it arises from the Strecker degradation of leucine.

3-deoxyglucosone (3-DG) is a compound emerging during the storage of sake, and is considered an important indicator of the degree of maturation. The range from 0.24-0.38 mM is considered appropriate: above this range, it is said that tasters begin to perceive  hine-ka .

The “burnt smell” (koge-shu (long “u”, 焦げ臭) sometimes occurring during storage is thought to be caused by esters from succinic acid, or amides.

The pleasant honey- or soy-sauce-like aromas arising during long-term ageing are due to sotolon or similar compounds, and are distinguished from hine-ka.