Sake from Koji - soup?

It's no secret that I have not yet managed to make a decent sake yet. Inevitably it comes down to the temperatures that I am currently capable of maintaining while fermenting rice and koji-kin. The previous batches have been sour, probably due to lactobacillus bacteria that creates that sour flavor.

But what if we were able to create a batch of sake that simply lacked the lactobacillus? Would we then be able to brew at room temperature as long as everything was sterilized? Let's find out.

I ended up leaving some koji rice in the fridge a little too long a couple of months ago. I opened it and noticed that the rice was turning into soup. It tasted very sweet and had that distinct koji-cheese smell. This started to make me wonder. What if we created a full batch of this koji soup, pasteurized it, then pitched our yeast? It would most definitely ferment. But what would it taste like?

Here is what I did:
Since I'm currently out of Cold Mountain Koji and this was a bit of a spur of the moment decision, I went ahead and used some more koji spores I picked up at the local homebrew supply to make my own koji rice. I soaked it, steamed it, let it cool, then sprinkled the koji spores on it mixed with a bit of flour to make spreading easier. It was left in a warm spot (heated with hot water bottles), and covered with a towel to keep it dark. That part went flawlessly. A couple of days later I had a large batch of koji rice ready to mix with another batch of freshly steamed rice.

The fresh was cooled to room temp, then mixed with the koji rice, then left alone for a bit. Two days later I opened it up to see the rice starting to liquefy like the batch I had in my fridge. After some digging, come to find out the enzyme produced by koji (amylaze) can still function at temperatures between 140 and 150 degrees farenheit. This made my job much much easier. I simply dumped this rice into a kettle, covered it, and let it sit at 140 degrees for a few hours until it turned into slush. All in all, I estimate the timeframe taking about 6-8 hours. I cooled it, put it in a sterile glass jug, then pitched the yeast.

I was unable to take an accurate gravity reading though. So I don't know exactly how much alcohol it was able to produce. There simply was too much rice floating in the slurry to allow the hydrometer to sink properly. But that's ok. This is only a test batch.

The yeast went crazy and completely fermented out in three days flat. I let it settle, siphoned off as much liquid as I could, then strained the rest. Out of the one-gallon jug I was able to get about 1.25 liters of liquid. The .25 was accidentlay spilled on my floor unfortunately. But that left a 1 liter bottle of something nigorizake like in my fridge.

It sat undisturbed for about 2 weeks, and then the day came when I couldn't take it any more. I simply had to sample it.

Into a small shot glass I poured a tiny sample. It smelled like a very mild sake so I sipped it. The flavor was good. It was a little strange though. It was still very sweet with a hint of sour. So I figured it would be time to let it settle more, rack it off, and see what it would become in the weeks to follow.

Last night I racked it off and sampled it again.

It's good. I mean good. It's not amazing, but I could most definitely drink this stuff. The ABV tastes around 8-10% so it is very mild. This would match the lack of liquid produced compared to the amount of rice used. The amylaze simply didn't break down the rice as well as I had hoped. But this was a very good ending to something that I truly had no idea how it would end.

Next week I'm going to order more Cold Mountain Koji and attempt this again. Expect this next time, it will be on a much larger batch with a lot more patience on my part. And I can't wait.