I have finally made a small batch of acorn spirit. In order to leech them I boiled the whole acorns whith the shells on, changing the water about five times, it was maybe around 3 hours of total boiling. This process also gelatinized them. Then I mashed them in a meat grinder into porridge. When the temperature was 65 C, I added amylase. I used a lot of amylase adding it several times. After processing this way for about one and a half hour, the mash was sweet enough even thoug the iodine showed that starch was still present. I used ca 5 kg acorns and added ca 2 liters of water. It fermented well whith distillers yeast, and I guess some conversion kept going on because the fermentation kept going for two weeks. I got ca. 1,5 liter 50 % spirit out of it. Distilling in a bain marie. The taste is great, acornish and different, but some test tasters did not like it. Closer to a grain spirit than potatoe, but the oils and flavor from the acorns give a bitter and nutty taste as well. I also tried an acorn fake mash, just boiling the acorns in the pressure boiler for an hour to gelatinize, and added spraymalt to reach 7 %. The taste of this was similar, but not as rich and complex as the proper one.
Next step I am going to try is to make a kind of acorn sake-mash. Aspergillus fungus that provides the amylase for starch conversion in sake, will also make tannase if tannine is present when the mold is growing. Tannase is an enzyme that brakes down tannine. I have bought koji spores to make kome-koji and have made a first try of ordinary sake of rice with great success. Im going to make a koji whith a mix of rice and acorn, and use this for a slow low-temperature conversion going on together whith the fermentatoin, in the same way as sake is made. I will update whith the results of further experiments.