Sweet potato sochu is very popular, especially in southern Japan. The process involves the inoculation of steamed sweet-potato slurry with a starter ‘Koji’ containing Aspergillus niger or A. kawachii as an enzyme source for starch conversion to sugars followed by fermentation to alcohol by yeast Saccharomyces cerevisiae.
The final alcohol concentration of the product is 13-15%. It is then pumped to the still and the alcohol is distilled off.
Sochu should not be confused with sake. Sochu taste usually far less fruity and depends strongly on the nature of the starch used in the brewing process. Its flavor is often describe as ‘nutty’ or ‘earthy’.
Sochu is consumed more by the poor than by the rich. On the other hand, special grade sake is by far a rich person beverage.
Sochu beverage
