One time a million years ago was the only time we ever purchased koji spores. As with our gardens and farms where the priority of seed saving carries us from one season to the next, hopefully adapting to the unique character of our land and weather, so it also made sense to foster that seed saving mentality to our spores and cultures.
Saving koji spores is as easy as growing koji because, well, they are the same thing. If you’re a grower of koji already then you can perhaps find the permission to follow through with your spore saving here.
To save koji spores we are simply looking for mature koji. I usually shoot for mature rather than over-mature as I feel better about a cleaner population. Many times I won’t even attempt to over-shoot my koji incubation, instead proceed with the process as usual, and put some aside for “seed” and it always ends up working fine. When growing your koji hopefully you can notice a bit of powder on the surface as that’s sign enough that’s ready. The bits I save from a batch are usually the best looking parts, with no discoloration or peculiarities. Those pieces are allowed to air-dry fully then they are bagged and stored in the freezer until the next time I make a batch of koji. To use them I’ll hand grind just before sprinkling on my newly cooked grain. And like any other culture, a little is saved again to keep it all going.