Koji is a mold that is at the heart of many different Japanese ferments. It is used to make miso, sake, amazake, rice vinegar, soy sauce and mirin. Koji is grown on rice or barley, which are then used as the starter culture for further fermentation.
Making homemade koji is quite straight forward. The most difficult part of making homemade koji is finding the koji spores (koji-kin). You may be able to find koji-kin in your local Japanese grocery store, or you can buy itonline. Just make sure that it’s koji-kin, not koji rice.
Once you have koji spores in your freezer, making koji rice or barley is fairly simple.
Koji rice (and koji barley) is used to make miso, sake, amasake, rice vinegar, soy sauce and mirin. Learn how to make homemade koji rice by growing koji kin mold on rice or barley.
Rinse your rice until the water runs clear (to remove all the starch).
Soak your rice in water for 8-12 hours.
Steam (not boil) the rice until it’s softened, but still sticky (see notes for advice).
Cool the rice to room temperature.
Thoroughly mix the culture into the rice.
Spread it out in a baking dish (to maintain the right amount of moisture). Cover with a damp cloth and maintain at 90 F (30 C) for 48 hours.
Stir every 12 hours to break up the clumps and evenly distribute moisture. It is finished after 48 hours, when white mold fibers start to develop. (Don’t let it go longer than that or it will spore).
Store in the freezer until you are ready to use it.
See below for incubation options and to learn how to save your own koji-kin mold spores for future batches.
Notes
Since this is a longer ferment it’s important to keep everything clean.
You can also used pearled barley, and follow the same procedure to make barely koji.
For steaming, I recommend using a vegetable steamer or colander lined with a tea towel. Just boil the tea towel in the steamer to sanitize it before using it to steam your rice.
Keywords: koji kin, koji barley, vegan, gluten free, sake, miso, soy free, nut free
Options for Koji Incubation
I have a Brød & Taylor Bread Proofer & Yogurt Maker, which I use for all my heated ferments. If you plan on doing a lot of fermenting, then I recommend making the investment. I use it for yogurt, cheese and tempeh.
Using a dehydrator or slow cooker set to 30C is also a great option.
Alternatively, you can try to grow your koji in the warmest location possible in your house. Perhaps in the oven with the light on, near a radiator or a hot water heater. The only trick is to measure the temperature as you go along, because koji mold will start to heat as it ferments. The right temperature is important because if it’s too cold your mold won’t grow, and if it’s too hot you will kill the spores.
How to Save Koji Mold Spores
Making koji-kin is easy. All you need to do is allow the koji mold to continue growing until it spores, then collect those spores. You will know that the koji-kin has spored when your koji turns from white to green. The green colour is the mold spores. Once your koji is green, then remove the damp towel, and allow the koji to dry out.
When the koji-kin has completely dried out, store it in the freezer for future batches of koji. When culturing future batches of koji, you only want to use the green powdered mold, not the rice, so sift the mold off of the rice before using it.
Hi Emillie, Thank you for your generosity in providing information and healthy recipes. I am interested in making Rice Koji and amazement. I have purchased a Brod and Taylor proofer and slow cooker all in one. I was just wondering if you have the same model do you use the proofer with water in the tray? Would be grateful if you could advise. Kind regards Paul
Hi Paul, I do have that Brod and Taylor. Though I’ve never put water in the tray, I use the proofer to cook my koji rice… and pretty much every ferment! It’s good at keeping a reliable temperature.
Thanks so much for your prompt reply Emillie. I will follow your advice seeing you have had success with it. Was glad to hear you can do other ferments too
Hi Eillie, Would be grateful if you could answer a couple more questions. The koji kin has arrived and just about ready to embark on my first ever rice koji. Re the baking tray- do you have to have a stainless steel tray or would a non stick tray be ok? Regarding other ferments do you put the glass containers in the Brod and Taylor for your ferment? There is a very quick recipe for Miso – it’s from the good british chef’s. They make it in 5 days. I have made it and it is quite light but tasty. Kind regards Paul
Hi Paul. You could use a non-stick tray. I haven’t tried it, but it should work. I would put the containers for koji rice in the Brod and Taylor, but not miso. I usually leave miso in a cupboard to ferment (because I leave it for 6 months!) Interesting about a quick miso. I might try that next time.
Thanks again Emillie. I thought you may have had to use a stainless steel tray. Yes, the quick miso recipe is an interesting one. It appears in a Japanese recipe using the Kuvings Yoghurt/ pickle maker. As I said it is light but I find it ok. Keep up your good work. Regards Paul
No… the risk of contamination is too great. Rice can contain Bacillus cereus which will cause food poisoning. You can buy koji online or at a Japanese grocery store.
Hello! I’m very much looking forward to making my first batch! If using a dehydrator, would we still want to cover the tray in a damp towel? If the dehydrator has a fan, should we turn off somehow? I’m a bit nervous about using it and wondering if it would be better to use the oven-light method instead. Thanks!
I have the same proofer. Though I’ve never added water to the little tray. I think that’s mostly for proofing instant yeast bread. I LOVE my proofer. Hope it works for you!
I already have rice populated with Koji that I’ve ordered from a Miso company I really like. Is there a way for me to propagate the same culture using the existing grain? My initial thought was to grind up a quarter cup or so into powder and use that as the starter.
The koji rice will be too diluted for a good culture. You need to collect koji spores. So culture your rice, and allow it to continue fermenting until the mold spores (usually about 48 hours into the ferment). At that point you can collect the koji kin spores from the rice (or just grind up the rice).
I actually haven’t done this myself, but it should work. Cheers, Emillie
Usually koji rice is used to make other ferments. Try amazake: https://www.fermentingforfoodies.com/archives/1044 If you are wanting to make koji kin, continue fermenting for up to 48 hours, then skim off the sporing mold from the top of the rice.
Thank you Emillie for your advice. I just tried today by putting 1 portion of the dried koji rice, one portion of cooked rice and water enough to soak them and put in an air tight container. Now i just have to wait for 48 hrs to see some spore.
Are you able to maintain the heat? If not, then it might take longer to grow. Also, I wouldn’t have the container air-tight. Just keep a lid loosely on so that it keeps the moisture in. Let me know how it goes!
I have had success with the Brod & Taylor proof box. I place a 9″ pyrex pie plate on the bottom to serve as a reservoir for hot water. This can be periodically exchanged/refilled The koji tray is supported above this by some cans of tomato paste at the periphery of the ”lower” level. I was able to harvest about 500g. I am not consistently successful in producing good steamed rice that is not clumpy. Is there a particular kind of rice that works best? Thanks
Hello after only 24 H my rice get totally wet soaked ! , it tastes sweet and has a good smell , but is nothing like it should be /see from pictures the more i leave it the watery it get , what do i do wrong ? bestsand thanks , stefano
Hum, I don’t know, since I’ve never had that problem. The steamed rice should be quite sticky but not wet. And the only additional water is from the damp cloth. It should taste sweet. So maybe just leave it with a dry cloth, or stop there?
I don’t have an insta pot, but I’m sure it would work! The only reason why it might not be the best, is transferring the yogurt from the insta pot to containers for storage will probably cause a bit of separation (yogurt from whey).
I’m not sure how the insta pot works, but I have nested jars of yogurt with lids on in my slow cooker. Then poured water halfway up the jar, and kept them warm that way.
Can I use Saccharomyces cerevisiae (bread yeast) instead of Koji-kin (Aspergillus oryzae)? Unfortunately, there is no chance to find Koji-kin in my area.
Sorry. Yeast is not the same as koji kin, which is a mold. Also trying to “catch” a mold culture is very risky. Which country are you in? You can often find koji online or in a Japanese specialty store.
I guess not. at least I don’t know, maybe there is. I’m a foreigner here in this country. After I have read your informative articles about fermentation, decided to try some of them in my free time. besides I love sake and can find plenty of excellent kinds of rice here to make it but…
Anyway, I enjoy your site and keep read your words…Thanks a lot for your kind replies
Emillie
Thanks!
Bronya
I was on another site and found that they will send it anywhere. i wasn’t really looking for that as I’m in Australia aand get it from an Australian site, but here is the link https://thejapanstore.jp/cart
The rice needs to be softened, but not too wet for the koji mold to culture well. I don’t think that soaking alone would soften the rice enough to culture.
Is the towel supposed to dry out? I am making koji now in a dehydrator, but I am worried that it wont work because the towel has dried out. Should I wet it?
Actually, I think some rice i still moist, so I will keep going and ee what happens. It seems that I have to keep wetting the tea towel every couple of hours which i a real pain
Sorry to hear about the difficulties with keeping the towel wet. What if you used two towels? Also, depending on how warm it is, you could just turn off the dehydrator. If the mold has started to grow it will generate some of its own heat.
Bronya
That is exactly what I am doing. I flicked a little water on it, mixed it in and put a second towel on and left it a couple of hours more. the towel had started to dry out, but had reached 41 degrees C so I broke up the clumps and left the heat off. It reached 40 degrees after about 5 hours – maybe sooner but I wasn’t able to check it earlier. It is starting to smell sweet and tastes sweet, but only about 1/4 of the grains have gone that stark white. I am pleased that it is working. it has now been going 50 hours but because of the way it looks I believe it needs longer. I will keep checking. I read that if you make Amazake with it and it works, you will know that it is OK. If I put it in the fridge then find it needs longer, do you know if I can keep going with the process?
By the way, I was thinking of buying the Brod and Taylor proofer and yoghurt maker to save further hassles. I clicked on the site and it was $169 US. As I’m in Australia I thought $240 Aus plus postage it might be worth it. But no, they wouldn’t let me order there because I am in Australia. If I go on the Australian Amazon site, it is $360 Aus. So unfair. I’m not going to get it. On some other sites it is even dearer. Not blaming you of course, just letting you know.
Sorry to hear that the Box is so expensive! It is rather large, so maybe that’s the issue with shipping? What a good idea to test your koji rice with amazake before trying a longer ferment. Besides amazake is delicious.
I think you should be able to continue culturing the rice after refrigerating. It will probably be a bit slow to start, but lots of my ferments pop in and out of the fridge.
Hum, clearly a dehydrator isn’t a great option. Do you have a yogurt maker or slow cooker? You might be able to vent them to get the right temperature.
hillel batafik
I bought some hulled barley as I thought it’s healthier than pearled. Will the recipe work for hulled barley?
I’ve never used barley with a hull on it. I don’t know whether the hull is too thick and hard for the mold to grow through. I wouldn’t think so, I don’t think of barley hulls as particularly tough. If you try it can you let me know how it goes? Thanks! Emillie
Hi Usama, I had some server issues last week, and it unfortunately erased everything that happened during those few days! Including your previous comment and my response. Sorry about that.
Anyways, koji rice is not the same as malt rice. Malt rice is rice that has been malted (sprouted, dried and then toasted.) The malting increases the accessible sugars. Malt rice is usually used for brewing gluten free beer or making malted rice syrup, which is a sweetener. I recommend buying malt rice if you need it for a recipe. Either at a homebrewing shop or online.
Alcohol is generally made when yeast consumes sugar. Miso is a mold based ferment (koji kin is a mold culture) so I don’t think it contains alcohol.
I understand that they advocate making amazake to test the koji rice but then you’ve used it up so there isn’t any left to make miso with? If you grow the spores from the koji rice (as you have suggested in the comments) how do we know how much is enough to make miso (especially if we just grind up the rice with them)? Surely this should be a continuous process-something we can continually make once you have the initial mold, whether from koji rice or kojikin?
You can’t use amazake or miso to make koji rice, however, you can make larger batches of koji rice. Just make as much koji as you need to make miso, amazake, etc. Then leave some of the koji rice to spore for future batches of koji kin. You can even freeze koji rice for future fermentation, so making extra is always a good thing!
My rice dried out and I re-wet it a few times. It grew more koji, but now some parts are a little too mushy and slightly pink. Should I be worried about the pink color? The rice smells good and a little sweet and a little funky. But I’m worried about the slight pink color and mushiness. I’m going to take off the towel, let it dry out, and see what it looks like. I also don’t seem to be getting big chunky bricks or fully inundated grains like I see in pictures, but it does look similar to your picture. What do you think? Should I start over? Maybe try and make amazake instead of miso?
Pink isn’t a good colour. If just part of it is pink, remove that piece and try making amazake with the rest. I’ll admit growing mold is a bit tricky. Maybe try a container with less ventilation so you can control the moisture a bit better?
 or colander
 or colander
lined with a tea towel. Just boil the tea towel in the steamer to sanitize it before using it to steam your rice.
Hi Emillie,
Thank you for your generosity in providing information and healthy recipes. I am interested in making Rice Koji and amazement. I have purchased a Brod and Taylor proofer and slow cooker all in one. I was just wondering if you have the same model do you use the proofer with water in the tray? Would be grateful if you could advise. Kind regards
Paul
Hi Paul, I do have that Brod and Taylor. Though I’ve never put water in the tray, I use the proofer to cook my koji rice… and pretty much every ferment! It’s good at keeping a reliable temperature.
Thanks so much for your prompt reply Emillie. I will follow your advice seeing you have had success with it. Was glad to hear you can do other ferments too
Hi Eillie,
Would be grateful if you could answer a couple more questions. The koji kin has arrived and just about ready to embark on my first ever rice koji. Re the baking tray- do you have to have a stainless steel tray or would a non stick tray be ok?
Regarding other ferments do you put the glass containers in the Brod and Taylor for your ferment?
There is a very quick recipe for Miso – it’s from the good british chef’s. They make it in 5 days. I have made it and it is quite light but tasty.
Kind regards
Paul
★★★★★
Hi Paul. You could use a non-stick tray. I haven’t tried it, but it should work. I would put the containers for koji rice in the Brod and Taylor, but not miso. I usually leave miso in a cupboard to ferment (because I leave it for 6 months!) Interesting about a quick miso. I might try that next time.
Thanks again Emillie. Really appreciate your help.
Thanks again for your help Emillie. I thought you may have had to use a stainless steel tray. I have made miso using the 5 day recipe from Kuvings.
Thanks again Emillie. I thought you may have had to use a stainless steel tray. Yes, the quick miso recipe is an interesting one. It appears in a Japanese recipe using the Kuvings Yoghurt/ pickle maker. As I said it is light but I find it ok.
Keep up your good work.
Regards
Paul
★★★★★
Thanks! I’ll look out for that.
can i make koji rice without koji spores
No… the risk of contamination is too great. Rice can contain Bacillus cereus which will cause food poisoning. You can buy koji online or at a Japanese grocery store.
Hello! I’m very much looking forward to making my first batch! If using a dehydrator, would we still want to cover the tray in a damp towel? If the dehydrator has a fan, should we turn off somehow? I’m a bit nervous about using it and wondering if it would be better to use the oven-light method instead. Thanks!
I have the same proofer. Though I’ve never added water to the little tray. I think that’s mostly for proofing instant yeast bread. I LOVE my proofer. Hope it works for you!
I already have rice populated with Koji that I’ve ordered from a Miso company I really like. Is there a way for me to propagate the same culture using the existing grain? My initial thought was to grind up a quarter cup or so into powder and use that as the starter.
★★★★
The koji rice will be too diluted for a good culture. You need to collect koji spores. So culture your rice, and allow it to continue fermenting until the mold spores (usually about 48 hours into the ferment). At that point you can collect the koji kin spores from the rice (or just grind up the rice).
I actually haven’t done this myself, but it should work. Cheers, Emillie
Emillie
I have a bag of dried koji rice. How should I culture it? Jus soak in water?
Usually koji rice is used to make other ferments. Try amazake: https://www.fermentingforfoodies.com/archives/1044
If you are wanting to make koji kin, continue fermenting for up to 48 hours, then skim off the sporing mold from the top of the rice.
Thank you Emillie for your advice. I just tried today by putting 1 portion of the dried koji rice, one portion of cooked rice and water enough to soak them and put in an air tight container. Now i just have to wait for 48 hrs to see some spore.
Did that sound right to you?
Are you able to maintain the heat? If not, then it might take longer to grow. Also, I wouldn’t have the container air-tight. Just keep a lid loosely on so that it keeps the moisture in. Let me know how it goes!
Hi Emillie,
I have had success with the Brod & Taylor proof box.
I place a 9″ pyrex pie plate on the bottom to serve as a reservoir for hot water. This can be periodically exchanged/refilled
The koji tray is supported above this by some cans of tomato paste at the periphery of the ”lower” level.
I was able to harvest about 500g.
I am not consistently successful in producing good steamed rice that is not clumpy. Is there a particular kind of rice that works best? Thanks
★★★★★
Great! Glad it worked for you. Not sure how to make rice less clumpy. The rice needs to be sticky.
Thank you Emillie for this great recipe. Can koji rice be made with brown/ red rice?
I haven’t tried it, but I think it should work.
Hello
after only 24 H my rice get totally wet soaked ! , it tastes sweet and has a good smell , but is nothing like it should be /see from pictures the more i leave it the watery it get , what do i do wrong ?
bestsand thanks , stefano
★★★★★
Hum, I don’t know, since I’ve never had that problem. The steamed rice should be quite sticky but not wet. And the only additional water is from the damp cloth. It should taste sweet. So maybe just leave it with a dry cloth, or stop there?
HI there, ever use the yogurt setting on an insta pot? I was thinking about trying that?
Thank you!
I don’t have an insta pot, but I’m sure it would work! The only reason why it might not be the best, is transferring the yogurt from the insta pot to containers for storage will probably cause a bit of separation (yogurt from whey).
I’m not sure how the insta pot works, but I have nested jars of yogurt with lids on in my slow cooker. Then poured water halfway up the jar, and kept them warm that way.
Heyo!
Im looking into growing my own spores from some locally made koji rice. You say to ‘culture your rice’. Could you explain what that means please?
This is the best resource I have found by far! Thank you so much for all your work. I can’t wait to try it out!
-Amanda
Thanks! Culturing means fermenting, or in this case allowing the mold to continue to grow. Does that make sense?
Hello Emillie
Can I use Saccharomyces cerevisiae (bread yeast) instead of Koji-kin (Aspergillus oryzae)? Unfortunately, there is no chance to find Koji-kin in my area.
Thank there
Sorry. Yeast is not the same as koji kin, which is a mold. Also trying to “catch” a mold culture is very risky. Which country are you in? You can often find koji online or in a Japanese specialty store.
Currently, live and work in ‎Yerevan, Armenia and sadly there is no Japanese specialty store in the city.
So there is no chance to make Koji without koji-kin, is there?
by the way, thank you so much.
Sorry, not that I know of. It’s probably a long-shot, but are there any online local forums where you might be able to post a “wanted” ad?
I guess not. at least I don’t know, maybe there is. I’m a foreigner here in this country. After I have read your informative articles about fermentation, decided to try some of them in my free time. besides I love sake and can find plenty of excellent kinds of rice here to make it but…
Anyway, I enjoy your site and keep read your words…Thanks a lot for your kind replies
Thanks!
I was on another site and found that they will send it anywhere. i wasn’t really looking for that as I’m in Australia aand get it from an Australian site, but here is the link https://thejapanstore.jp/cart
Hi,
does it nesesary to steam rice,
can we skip that step?
And if we cant skip, whay we need to steam?
THank you.
The rice needs to be softened, but not too wet for the koji mold to culture well. I don’t think that soaking alone would soften the rice enough to culture.
So, in thery, I need to found way to soften rice or barley or corn etc. but not to be too much wet. Sounds posible 😀 Thank you.
Is the towel supposed to dry out? I am making koji now in a dehydrator, but I am worried that it wont work because the towel has dried out. Should I wet it?
I would re-wet the towel. The dehydrator does increase the risk of it drying out.
Thank youso much for being so prompt and thanks for your very imformative site.
My rice dried out. Do you think it is ruined, or should I try to keep it moist and keep going?
Actually, I think some rice i still moist, so I will keep going and ee what happens. It seems that I have to keep wetting the tea towel every couple of hours which i a real pain
Sorry to hear about the difficulties with keeping the towel wet. What if you used two towels? Also, depending on how warm it is, you could just turn off the dehydrator. If the mold has started to grow it will generate some of its own heat.
That is exactly what I am doing. I flicked a little water on it, mixed it in and put a second towel on and left it a couple of hours more. the towel had started to dry out, but had reached 41 degrees C so I broke up the clumps and left the heat off. It reached 40 degrees after about 5 hours – maybe sooner but I wasn’t able to check it earlier. It is starting to smell sweet and tastes sweet, but only about 1/4 of the grains have gone that stark white. I am pleased that it is working. it has now been going 50 hours but because of the way it looks I believe it needs longer. I will keep checking. I read that if you make Amazake with it and it works, you will know that it is OK. If I put it in the fridge then find it needs longer, do you know if I can keep going with the process?
By the way, I was thinking of buying the Brod and Taylor proofer and yoghurt maker to save further hassles. I clicked on the site and it was $169 US. As I’m in Australia I thought $240 Aus plus postage it might be worth it. But no, they wouldn’t let me order there because I am in Australia. If I go on the Australian Amazon site, it is $360 Aus. So unfair. I’m not going to get it. On some other sites it is even dearer. Not blaming you of course, just letting you know.
Sorry to hear that the Box is so expensive! It is rather large, so maybe that’s the issue with shipping? What a good idea to test your koji rice with amazake before trying a longer ferment. Besides amazake is delicious.
I think you should be able to continue culturing the rice after refrigerating. It will probably be a bit slow to start, but lots of my ferments pop in and out of the fridge.
Thanks, I’ll let you know how the amazake goes. I’ll make it tomorrow.
It is not the shipping; it is just that in Australia we get ripped off. Not sure why. It happens even for light weight products.
I think the amazake dried out. Not sure that it worked. May have to try again.
Hum, clearly a dehydrator isn’t a great option. Do you have a yogurt maker or slow cooker? You might be able to vent them to get the right temperature.
I bought some hulled barley as I thought it’s healthier than pearled.
Will the recipe work for hulled barley?
I’ve never used barley with a hull on it. I don’t know whether the hull is too thick and hard for the mold to grow through. I wouldn’t think so, I don’t think of barley hulls as particularly tough. If you try it can you let me know how it goes? Thanks! Emillie
Hi
I have a few questions, and please answer them.
1-Is koji rice the same thing as Malt rice? If isn’t: can you tell me what the malt rice is and how we can make it?
2-Does miso contain alcohol?
Hi Usama,
I had some server issues last week, and it unfortunately erased everything that happened during those few days! Including your previous comment and my response. Sorry about that.
Anyways, koji rice is not the same as malt rice. Malt rice is rice that has been malted (sprouted, dried and then toasted.) The malting increases the accessible sugars. Malt rice is usually used for brewing gluten free beer or making malted rice syrup, which is a sweetener. I recommend buying malt rice if you need it for a recipe. Either at a homebrewing shop or online.
Alcohol is generally made when yeast consumes sugar. Miso is a mold based ferment (koji kin is a mold culture) so I don’t think it contains alcohol.
Cheers, Emillie
I understand that they advocate making amazake to test the koji rice but then you’ve used it up so there isn’t any left to make miso with? If you grow the spores from the koji rice (as you have suggested in the comments) how do we know how much is enough to make miso (especially if we just grind up the rice with them)? Surely this should be a continuous process-something we can continually make once you have the initial mold, whether from koji rice or kojikin?
You can’t use amazake or miso to make koji rice, however, you can make larger batches of koji rice. Just make as much koji as you need to make miso, amazake, etc. Then leave some of the koji rice to spore for future batches of koji kin. You can even freeze koji rice for future fermentation, so making extra is always a good thing!
Hi! Thanks for your helpful instructions.
My rice dried out and I re-wet it a few times. It grew more koji, but now some parts are a little too mushy and slightly pink. Should I be worried about the pink color? The rice smells good and a little sweet and a little funky. But I’m worried about the slight pink color and mushiness. I’m going to take off the towel, let it dry out, and see what it looks like. I also don’t seem to be getting big chunky bricks or fully inundated grains like I see in pictures, but it does look similar to your picture. What do you think? Should I start over? Maybe try and make amazake instead of miso?
Pink isn’t a good colour. If just part of it is pink, remove that piece and try making amazake with the rest. I’ll admit growing mold is a bit tricky. Maybe try a container with less ventilation so you can control the moisture a bit better?