- Colour and clarity
The colour and clarity of sake are collectively known by the technical term shiki-taku (色沢), and, like taste and aroma, are important indicators of quality. A number of specialist expressions like sae and teri refer to the clarity (“brightness” or “brilliance”) of the sake. In the case of the shiki-taku of brewing water, it is preferable that it be colourless and clear.
The greater part of sake colour deriving from the raw materials (rice, rice koji kome koji and yeast) comes from riboflavin (also known as vitamin B2)、a member of the flavin group of organic compounds.
The yellowish green colour of new sake (shinshu, known by the specialist term ao-zae 青ざえ), is the colour of flavin, but can be almost entirely removed using activated carbon. When sake ages, melanoidin and other browning agents increase, so the relative influence of flavins decreases, and sake colour becomes dominated by reddish brown hues.
Most sake is treated until almost colourless using activated charcoal, and such sake is accepted as the desirable standard in the market. On the other hand, excessive use of carbon in filtration can have the negative effect of removing depth and richness of flavour. Recently, it has become increasingly common to limit or omit filtration, with the intention of retaining as much rich, full flavour as possible.
When it is wished to assess quality without being influenced by colour or clarity, a brown glass tasting cup (“amber glass”) is used for tasting. In this case, it is hardly possible to detect differences in colour, and cloudiness is also harder to see.