How to Make Koji 4: Inoculation to Start Incubation


What happens if you let your rice temperature drop under 43C/110F? That’s not a huge disaster, but the reason why 43C/110F (or even 45C/113F sometimes) are recommended for the inoculation timing is that rice does get cooler and cooler while you are inoculating. The cooler they get, the drier they get. Moisture is the last thing youn want to lose, as it’s one of the essential sources for koji to thrive. After all they are mold and the mold doesn’t grow on dry things.
Another reason why it’s good to start while rice is a bit warmer than your hand is, you’d probably end up with over 32C/90F when you are all done with inoculating. This is good, because below 32C/90F doesn’t only mean that your rice lost a lot of moisture but also means you took too much time to inoculate and any other microbes present in your environment could have had enough time to jump on cold and wet surface of rice. You would make your best effort to avoid this, unless you are working in a dedicated clean room (like tane-koji or pro koji-makers have).
So in short, for time, contamination and optimal moisture level, you’d better off start inoculating while rice is still nice and warm.



Remember your koji making may not work out easiest from the beginning, but it’s all for you and koji to introduce each other. Enjoy the introduction, and keep notes of what you have tried. After you wrap your rice in a cloth, insert your thermometer prob into the centre of rice. The thermometer with a long cable comes handy, so you can monitor the temperature of koji without opening the wrap each time you wonder. Finally, wrap it with a plastic bag to ensure the minimum amount of moisture until koji-kin germinates on rice. The moisture is the key at the beginning of koji making, so keep it moist (but not wet) and warm, be around and make sure your rice stays around your body temperature in next 12 hours.
This is the moment your incubation starts. Check our clock and monitor the progress by hour count. This step to wrap your rice and start incubation is called “tsutsumikomi” or “hikikomi”, depending on the volume. Refer to the previous article for the desirable condition of incubation box to set up your own muro.
