The Japanese have used successfully used cooked rice and mashed/grated
raw sweet potato tubers as the saccharifying agent to make an
Raw sweet potato has diastatic activity, and a 10-20% addition to
cooked rice (or other grains) would be an adequate alternative to
If using only sweet potato, a source (Journal of Food Science, 1986)
"These results suggested that rapid heating of sweet potato mashes to
80 degrees Celsius may be optimal for starch conversion and handling
of sweet potato mashes prepared for ethanol fermentation."