- Degree of clarity
Along with taste, aroma and colour, the degree of clarity is an important indicator of seishu quality. Impurities in sake do not only affect its clarity, but have a great negative impact on its commercial value. The main causes of cloudiness are protein turbidity (tanpaku kondaku) and the bacterial contamination hi-ochi.
Protein turbidity is caused by saccharifying enzymes from koji, which precipitate because of heating and subsequent cooling during pasteurization. Ori-sage fining and filtration are carried out before bottling to prevent it.
Hi-ochi occurs when the kind of lactic acid bacteria known as hi-ochi kin multiplies in the sake, turning the clear sake milky. Sake thus contaminated is not drinkable, so the sake needs to undergo treatment for the cloudiness, odour and excessive acidity to be returned to an acceptable state.