Imojochu (Sweet Potato Sochu)
- Imojochu is a Jpanese spirit distilled from sweet potatoes. Sweet
potatoes average about 22% starch and 5-6% sugar for a total of 27-
28% fermentable material which makes them a better source than
potatoes which contain 15-18% fermentable material.
The actual production for imojochu involves 4 steps:
1) Koji (inoculated rice) production -
This requires about 40 hours, during which polished rice must be
steamed and cooled, and koji-kin (Aspergillus oryzae) added.
2) First fermentation -
Water and yeast are added to the koji and the resulting mix is
allowed to ferment for about 1 week.
3) Second fermentation -
The mash, now known as moromi, is combined with sweet potatoes
(steamed, cooled, mashed) and water. This is fermented for 9-10 days.
There is a potato/sweet potato recipe in 'Home-brewing of Sake'
I have scaled-up the recipe for 20 litres (5 US gals):
Sweet Potato Mash
12 kg sweet potatoes
1.5 kg sugar
15 cups of dry koji
20 litres water
Cook potatoes and mash.
Add 1/3 water.
Add 1/3 koji and stir.
Allow koji to saccharify the starch.
After day 4, add rest of ingredients.