Dried Koji Experiment

While I was out on the west coast for vacation I made sure to visit Japantown in San Francisco. No visit to Japantown is complete without stopping in a Japanese grocery store. Guess what I found next to the miso in the cooler?

Cold Mountain Dried Koji! Score! (again haha! it was a GREAT vacation)

This stuff is hard (impossible) to find in Dallas and it seems we may have to order it online. Brian snagged a bucket earlier for his 2nd batch of sake but with shipping the $6.99 price for a bucket of koji jumps up past $20. Boo! I bought 2 at the store and brought them back in my suitcase.

I was concerned about the temperature variations on the trip home since these were in the cooler at the store, but they're totally dehydrated and after a quick consultation Brian we decided it would be worth the risk. Needless to say, everything turned out fine. I found that out tonight as you'll see.

Once I got home I had this idea that I wanted to propagate my own koji to make koji-kin (the spores). The idea is that if I could make my own koji-kin I could make any amount of koji I need from it to brew any amount of sake. I wasn't sure if I could do that with what seemed to be freeze-dried koji. Would the koji fungus be ok? Does it die after dehydration? Are there any spores left on the dried koji that would start growing?

All these questions were indirectly answered tonight... when I saw the results of 24 hours of microbiological goodness. Needless to say, there's money riding on this experiment. If it works it means my homebrewed sake can be even less expensive. In today's economy that's a good thing.

The Experiment

Yesterday I took 1 tsp of the dried koji and put it in a small glass with just enough water to cover it. Yes, that's ONE TEASPOON! A seemingly tiny amount in comparison to the bucket-o-koji. My idea was to rehydrate it just to the point where the starches in the kernels of rice would gelatinize again. Then I would let it incubate for a couple days to find out if there was any dormant koji still in there.

After a few hours the dried koji soaked up all the water and was looking about right. I added a tiny bit more water and put the glass with the rehydrated koji on top of some shelves that have a warm plant light in them so it would be slightly above ambient at 80-85 degrees F.

Next time I do this I'll measure everything since I know it works and I'll post more details and instructions for reproducing my results.

Here's what I found an hour ago: koji fur!!

You can see the fur forming at the top of the photo where the rice is becoming white. And now for the money shot:

It looks like this method works! I will let this tiny test batch of rehydrated koji continue on to the next part of the experiment - spores. I have no doubts now that I can buy a bucket of dried koji and eventually end up with my own batch of koji-kin. Hopefully those were the last 2 buckets of koji I will ever have to buy!