Getting started with koji can be really intimidating. At least it was to me. I love fermentation, and koji has crept into my mind slowly over time. I became especially intrigued with the thought of making my own soy sauce, so down the rabbit hole I went.

Since I've started I've grown koji on long grain rice, jasmine rice, basmati rice, barley, farro, Minnesota wild rice, and soybeans & wheat. I've played with A. oryzae, sojae, and luchensis. I've made various types of shoyu/shio koji, koji butter, koji cured egg yolks, mirin, amazake, regular shoyu, black soybean shoyu, miso, peaso, and blackened koji. I'm working on another miso, peaso, and black soybean miso. I would say I'm an advanced newbie to koji, so y'all can probably take this with a grain if salt if you want, but here's for anyone who is still with me.

My first concern was setting up an incubation chamber, but the more research I did, the more I realized this DIDN'T need to be anything high tech, or require a huge monetary investment. I wanted to post some details of my setup, some basic instructions, and tips and tricks I've come across and figured out. I also post links to some products at the bottom.

The basic requirements of your fermentation chamber will be retaining heat and humidity.

Simple and cheap option for retaining heat and humidity? Coolers. Got an old cooler around? Don't use it often? Use it for koji. Don't have one? Buy one, or buy a Styrofoam cooler. I bought my foam cooler from Wal-Mart, they were $19. I actually bought 4 of them, but when I'm not using them for koji I can use them to store some of my fermentation stuff. You can also use things like old mini-fridges, chest freezers, anything that is insulated. The better insulated, the better it'll hold in the heat and the less you'll have to rely on your heating element.

This brings me to my next point, heat. I personally use a seedling heating mat connected to a temp controller unit. Many of people use Inkbird controllers and reptile heat mats. I linked mine down below, it's by Luxbird, and it includes 2 heat mats plus the probes and controller for less than $50 USD as of Sept. 2024. They work well and it controls each heat mat independently. You can set a max temp, min temp, and set alarms in case the temperature gets too high or too low.

Humidity is the next part. A lot of people do buy humidifiers to help keep humidity up in their chambers, but I find the foam cooler and a few tricks keep humidity up just fine.

First, make sure your substrate is well hydrated (without being too wet, koji will drown and not grow if things are too wet). This will provide a lot of ambient humidity for the koji. Second, wrap your koji in damp towels or cheesecloth. Don't leave the cloth dripping wet, wring it out. Again, koji can drown. Third, if you find your humidity is lower than you'd like, spritz the chamber with water or consider leaving a container of water on the bottom on top of the heater. I use a basic temp/humidity sensor linked below to monitor. I try to keep my koji at 85-90% ambient humidity the first 24 hours. After that point (when I have noticeable growth) I let humidity fall to the least of my concerns, whereas controlling heat becomes the top priority 24+ hours in. Koji can and will heat itself to death. This setup isn't high tech so you'll want to plan your 24+ hours to be something where you can easily monitor temperatures and help the koji cool down if needed.

What to place your koji in can be the next question. I see a lot of people using perforated half hotel pans. These are a great option and will help your koji breathe as it grows. Koji needs oxygen like we do. Once I discovered that I liked koji, I decided to invest in some cedar trays. I linked the shop I used down below, they made me some custom 17"x12"x3" cedar trays, and I'm wildly happy with them. They're not fancy or artistic, but they're exactly what I asked for, they work perfectly for koji, and they're solidly built. They were very reasonably priced. Contact the owner for customized sizes, he's great! I love my cedar trays because they're easy to use, easy to clean, they help the koji breathe, and it's an homage to traditional koji methods. I keep my trays elevated off of the heat mat with simple cooling racks that I have at home.

Once you have your chamber, heat, humidity, and trays figured out, the next question is spores. There are a lot of spore options out there, along with places to purchase (depending where you live). I recommend fermentationculture.eu. I have personally bought soy sauce koji spores from them, and A. sojae spores.

Finally, you need your medium. Are you trying plain long grain rice? Pearled barley? Soybeans? Farro? Quinoa? Pinto beans? Black eye peas? Figure out what you want to do and go from there.

I'm including some simple instructions below for both my normal rice koji, which can be adapted to barley koji, the steps I follow for shoyu koji (soybeans and wheat for shoyu), a recipe for mirin, another easy koji product, and basic shio and shoyu koji.

RICE KOJI

Ingredients: Long grain rice, the amount is up to you and your trays, steamer, and needs (if using barley, use pearled barley) White koji spores

Steps 1. Rinse long grain rice well to remove powdered starch from the grains. If you do not do this your rice may clump up. The koji cannot grow into big clumps of rice well. 2. Soak rice in cold water until the grains can be split by a fingernail, this is typically 3-4 hours for me. Might be overnight. 4. Rinse rice again. You do not want clumps! 4.5 (Optional) Lay rice out in an even layer on a pan and dry 1-2 hours, stirring once or twice to help all the rice dry a bit. I am lazy and do not do this, but some people do. It helps with clumps. 5. Steam rice in your preferred method until al dente. You do not want the rice as soft as you would for eating, it still needs to have a bite. This might take some practice. The grain needs to be wet and soft enough for the koji to be able to penetrate it, not not wet enough that it clumps and the koji cant penetrate it without drowning. Mix rice throughout steaming to make sure it cooks evenly and that you maintain a grainy texture. You do not want clumps. This may take an hour or two, depending on the amount of rice you're steaming and your method. 6. Put rice in a large bowl to cool to at least 30°C/86°F. 7. Inoculate rice with spores per directions on spores (the spores will give you directions for dilution and how many g/kg of spore/substrate you need to inoculate, example 1g spore per 1000kg substrate). Mix very well. It helps to dilute and dust the spores in small increments, mixing well between dustings. 8. Spread a damp towel or cheesecloth in your koji tray, and spread rice in an even layer (you can leave it in a pile to do it a more traditional way). You do not want koji more than 1-2" thick in your tray when spread out evenly. Thinner layers are easier to keep cool. 9. Put a thermometer probe in the middle of your koji, cover with another damp cloth, and put in your incubation chamber. Set your controller to no more than 32°C/89°F. Aim to keep your koji between 27°C/80°F and 32°C/89°F. Koji can and will heat itself to death later in its growth (temps greater than 45°C/113°F). I tend to set my temp controller to come on at 27°C/82°F, and go off at 29°C/85°F. During this time you want to keep humidity high, like 80-90%. Spritz as needed. 10. Check koji after 24 hours and mix. If you have made your koji into a mound, spread it evenly in your koji tray now. Your koji will start to generate much of its own heat at this point. Cover, and monitor temperatures. If it starts getting too hot, an easy way to bring temperature down is to take the koji out of the cooler and place it on a solid, uninsulated surface like a counter. You can also place ice packs under the tray in the cooler to help maintain a cooler temperature. Humidity is less important at this point as you want the koji to grow into the substrate looking for moisture. Barley koji heats up quicker and hotter than rice koji! 11. Let the koji grow for up to 48 hours. Your koji is done once it is a thick, fuzzy white mix of substrate and mycelium. Try to get it just before it sporulates to maximize enzyme production. 12. Put the koji in the refrigerator to stop the growth. 13. Enjoy! Use koji as desired.

BASIC SHOYU Ingredients 1000g dry soybeans 1000g soft white wheat berries 2000g water 720g sea salt

Steps 1. Rinse and pick through soybeans, then soak in cool water overnight. 2. Drain and rinse soybeans. Place in large pot and cover with water. Set on stove to boil, topping with water as needed. Boil soybeans for 4-6 hours, until soft enough to mash between your fingers. Reserve 1/2 cup of soybean water. Drain soybeans, place in large bowl, and cool. 3. Toast wheat berries. I toast them in a pan on the stovetop, some toast it in the oven. The choice is yours. I feel I have more control on the stove. 4. Crack the toasted wheat berries. I place them in a food processor or blender until roughly cracked. You do not need it to be a fine powder. 5. Combine soybeans, cracked wheat berries, and 1/2 cup soybean water. Mix well. Allow to cool to at least 30°C/86°F. 6. Inoculate rice with spores per directions on spores (the spores will give you directions for dilution and how many g/kg of spore/substrate you need to inoculate). Mix very well. 7. Spread damp towel or cheesecloth on your koji tray, and spread koji in your tray. You do not want your koji more than 1-2" thick in your tray. Thinner layers are easier to keep cool. 8. Add thermometer probe to the middle of your koji, and incubate for 24 hours in your chamber. Aim to keep your koji between 27°C/80°F and 32°C/89°F. Koji can and will heat itself to death later in it's growth (45°C/113°F). I tend to set my temp controller to come on at 27°C/82°F, and go off at 29°C/85°F. During this time you want to keep humidity high, like 80-90% 9. After 24 hours mix your koji. At this point your koji will start to heat up significantly. You can reduce the heat in your koji by forming rows in your mix, mixing more frequently, placing your tray on a non insulated surface, and/or adding ice packs if necessary. Soybean/wheat mix koji heats up faster than plain rice or barley koji! You need to control humidity less at this point. The koji will begin seeking moisture from inside the grain and soybeans. 10. Allow your koji to grow 48-96 hours. Try to pull before there is too much sporulation, this can cause unwanted flavors. Some sporulation is fine. I find that A. sojae sporulates faster than A. oryzae. Your koji is done when the substrate is covered in a thick layer of white fluffy mycelium. Place koji in the fridge to stop growth. 11. Mix 2000g of water with 720g sea salt in a large jar until all the salt is dissolved. 12. Mix in koji mix, stirring well. 13. Cover well, and mix well every day for a month. Then mix every other day for a month, then move onto every third day for a month, and then move onto weekly for the remainder of the time. 14. Allow to process for at least 6 months. 12-18 months is better. Strain and filter the moromi (soybean/wheat mash) from the soy sauce. 15. Bottle and enjoy.

Mirin Ingredients 500g COOKED short grain/glutinous/sweet rice. 500g koji 1000g shochu (or vodka, or any other neutral tasting spirit 25-40% ABV/50-80 proof)

Steps 1. Cook glutinous rice, weigh out 500g of cooked rice. You do NOT have to steam the rice. 2. Combine 500g of cooked glutinous rice with 500g of prepared koji into large jar. Mix well. 3. Add in 1000g of shochu. Mix well. 4. Allow to age at least 6 months. 12+ months is better. 5. Strain off mirin from mirin lees (leftover rice pulp). 6. Bottle and enjoy.

Do not throw out the moromi or mirin lees! You can also use these like you do shio koji for marinating things like vegetables and meat. Koji, the gift that keeps on giving.

Shio Koji

Ingredients 500g koji 500g water 100g sea salt

Steps 1. Add salt to water, stir until dissolved. 2. Stir daily on the counter for 10-14 days. Taste the shio koji daily after stirring. Stop when it tastes good to you. 3. Put ship koji in the fridge. Use as a marinade or ingredient. *you can use a range of salt. I make it 10% salt for my purposes. You can try 5% if you want.

Shoyu Koji

Ingredients 500g koji 500g soy sauce

Steps 1. Combine ingredients, stir well. 2. Allow to sit on the counter for 10-14 days, stirring daily. Taste daily and stop when it tastes good to you. 3. Put in the refrigerator when it is done. Use as a marinade or ingredient.

-The basic shoyu ratio is 1:1:2 dry soybeans:wheat:water.

-Mirin is 1:1:2 cooked glutinous rice:koji:shochu.

-Shio Koji is 1:1 water:koji, plus about 10% salt.

-Shoyu Koji is 1:1 soy sauce:grain. Soy sauce has sufficient salt in it already.

-A. sojae sporulates green -A. oryzae sporulates yellow -A. luchensis sporulates black

NOTES -A. oryzae will die when temps are below approximately 24°C/76°F, and when temps are above 45°C/113°F. -Higher temperatures produce more amylases and lower temperatures produce more proteases. -Higher temperatures also prompt the koji to sporulate sooner, reducing enzyme production.

LINK LIST

Styrofoam Cooler: https://www.walmart.com/ip/Lifoam-48-Can-Huskee-Envirocooler-Foam-45-Qt-Cooler-White/485438903

Heating, Luxbird system: https://a.co/d/6xp4Gv4

Temp and humidity sensors: https://a.co/d/5vngjiV

Cedar Trays: https://www.etsy.com/listing/1778523248/solid-bottom-cedar-tray

Spores: https://www.fermentationculture.eu/shop/?

Can't get enough koji? Many r/Koji members are swapping ideas over on the koji Discord chat and everyone is welcome to join: https://discord.gg/FQ9f5NKrBa