- Colouring agent
Causes of colouring in sake can be broadly categorized as follows.
Mainly riboflavin (vitamin B2). Relatively prevalent in shinshu, giving it a pale yellow colour with a slightly blue-green cast.
- Melanin-related pigments.
From melanoidin produced by the polymerization of sugars and amino acids (amino-carbonyl reaction). The higher the levels of sugar and amino acid in a given sake, the faster such factors as storage temperature, length of storage and the degree of exposure to light after bottling will take effect, with the sake taking on yellowish-brown colour.
The cyclic peptide deferriferrichrysin (produced by koji -kin) undergoes a chelate reaction with the ferrous ions present in the sake The resulting ferrichrysin gives a reddish-brown colour.
The bulk of these sources of colour are derived from the raw materials, kome-koji and water, and decrease or increase depending on the progress of the brewing process and storage conditions to make up the shiki-taku (color and lustre) of the sake.