Which koji should I buy?

I’ve been asked, understandably, which koji to buy. A choice of 9 different strains may be a bit overwhelming when one is just starting out.

The most important thing to know is what you are most likely to make with the koji. Do you want to make barley miso, rice miso, soy sauce, amazake, etc.?

Generally speaking, rice koji will grow on soy beans too. It is a bit like buying vegetable seeds in southern Spain. They are meant to be grown there, but they will also grow in Austria – albeit just not as well.

In Japan koji has been bred to fit different applications, i.e. for soy sauce, for different misos, sake etc. So some strains have been bred to produce a lot of amylases, some to produce a lot of proteases, others to grow fast and on “difficult” substrates.

If you are planning to make sake (needs strong amylatic power) and soy sauce (needs lots of proteases), you are best off buying two strains. If you want to make rice miso and amazake, you are served well by just buying one strain.

I am sure can grow barley koji on rice too – might be worth an experiment!

The 9 strains explained

Which of the 9 kojis you should choose really depends on what you are planning to make.

Strains for miso:

Light Rice Koji

This is the strain to get if you plan to make short term sweet misos, amazake and/or sake. Sweet misos are misos which don’t ferment for very long (from 2 weeks to two months) with a relatively low percentage of salt.

This strain has strong amylatic power.

Red Rice Koji

This strain has been bred to best suit long term rice misos, also called red rice misos. These misos ferment from 6 to 12 months and contain more salt.

Compared to the light rice koji, this one has stronger proteatic power but less amylatic power. The strong proteatic power helps to make the miso as delicious as possible.

Barley Koji

This strain is probably my favourite to make. It just smells so good! Incidentally barley miso (also called mugi miso) is my favourite miso, too. It ferments from 4-12 months.

As the name says it is best suited for barley, which is a more “difficult” (for the fungus) substrate than rice. So this strain has been bred to grow easily on pearled barley.

Amylatic and proteatic power are both at a similar level.

If you’d ask me which strain you should buy if you just want to buy one – I’d say either this one or red rice koji, depending on which miso you like better.

Soy Koji

Some misos are made exclusively with soy beans – a difficult substrate for the fungus. These misos also take the longest to ferment, from 12 to 24 months. This strain has been bred to fulfill the needs of this application, it grows best on soy beans and has strong proteatic and medium amylatic power.

Strains for soy sauce:

Soy sauce Koji

If you are planning to make soy sauce, I really recommend getting this strain.

Soy sauce is made by toasting wheat, breaking it up, mixing it with steamed soy beans and then growing koji on it. Needless to say that is not an easy substrate for the fungus, but this strain has been bred to grow best on a substrate like that within a considerable time.

My supplier has this strain running under the name “three-dia”, because it takes only three days to grow, other than the usual four days for such an application.

With soy sauce there are more factors in what is needed from a strain. Low sugar consumption is wanted – to leave more in the final sauce/for yeasts. Also high proteatic power is needed, so suppliers breed specifically for these needs.

Mild Soy Sauce Koji

The normal soy sauce strain can be really vigorous, and for that reason it is prone to overheating. This strain grows more slowly, which is why beginners might find it easier to use. This is the reason it is called “mild”. The soy sauces you make with this strain will be no less strong than the ones you make with the normal strain.

A. Sojae

This is actually a different species, called Aspergillus Sojae. I provide this strain for people who want to change it up a bit. It is traditionally used for pale soy sauces and is said to have a different characteristic smell and taste.

If you are making soy sauces – try it! If you are starting out and want to make miso it may be better to stick to other strains. However it might be an interesting experiment to make miso with this one.

Other strains:

White Koji

This is a strain that is primarily meant for Amazake. I think of all the Koji strains I offer, this one smells best: flowery and mushroomy. While this strain is primarily for Amazake, I have made miso with it as well and it was good, too!

Black Koji

This is not A. Oryzae, but A. awamori. Traditionally this fungus is used for making shochu, a distilled drink either made from rice, barley or sweet potato. Unlike regular Koji, it produces citric acid. The acid helps to lower pH to make the amylases more effictive (their optimum is between 4.2 – 4.8 or so).

So this strain is for you if you want to make shochu, or if you want to experiment with a strain that has a black color and produces citric acid.

I hope this article helped to make your choice! If you have any questions, ask away :)

This Post Has 38 Comments

  1. Do you source your koji from Higuchi Matsunosuke? I have seen that they also have the ‘three dia’ koji for soy sauce.

    1. Hi Julius,
      yes, I do.

  2. You say that for sake “you are best off buying two strains”. Do you mean two packets of one strain, namely Light Rice Koji?

    1. Hi Mark,

      I meant that you will need two different strains if you are going to make amazake and soy sauce, i.e. you need light rice Koji spores and soy sauce Koji spores.

  3. To age miso like a white variety, what wooden containers are suitable?
    Are old recycled white wine barrels suitable, made from French oak?

    Also if I were to make wooden trays for koji growth what are suitable wood varieties

    1. Hi Mark,

      First off, I have no experience with wine barrels. Does the wood soak up a lot of moisture? If you were to age your miso in a barrel and the wood soaks up a lot of moisture you run into the danger of moldy miso I think.
      That being said, in Japan they traditionally age miso in wooden barrels. So it is definitely possible!

      For my trays I used spruce, as it is widely available around here. In Japan they use cedar. Any soft wood will do.

  4. Hello, thank you for sharing your knowledge about Koji! I am making my own rice wine and have been using shop bought Miyako Koji, but wanted to experiment with something different. Which koji would you recommend, and would I be able to use it in the same way? In other words do I just add it to the cooked rice (and water etc), or do I need to use the koji spores to make rice koji first? Thanks!


    1. Hi Lan,

      I’d try either the White Koji or the Light Rice Koji.
      You will have to grow the fungus on the rice first!

      Finished Koji rice will be available by April 2019 =)

  5. Thank you for this informative article! I’m wondering if you’ve ever had experience with aspergillus luchuensis. Based on an interview I heard on Cooking Issues it’s supposed to give very fruity notes. The guest, a guy from Noma, described it as tasting like fruit loops on speed. Which sounds amazing to me- I had some early experiences homebrewing at inadvisably warm temperatures (to get that beer faster) and discovered amazing fruit notes coming off the yeast. I would love to learn more about luchuensis and get my hands on it if at all possible.

    Thank you again for your valuable insights.

    1. Hi William,

      I know what you mean about the fruitiness. I do get it in my shoyus quite a lot. Before pressing it it is super fruity, after pressing more mushroomy. In that case the fruitiness is, like in the beer, due to the yeasts producing various esters.
      I have gotten a few requests for A. luchuensis, and I am going to contact my supplier to ask if they have it.
      Meanwhile, I found that the white Koji on pearl barley smells wonderfully flowery :)
      I will let you know once luchuensis is available!

      Kind regards,

  6. Which Koji is Asperligus Orzyae

    1. Hi Surinder,

      every Koji is Aspergillus Oryzae, except Black Koji, A. Luchuensis and A. Sojae.

  7. Hello Viktor,
    I am not looking to make soy sauce or miso out of my koji, Im trying to experiment with Koji in desserts. With that being said, which strain would I get the sweeter products out of? Thank you!

    1. Hi Erick!

      I would definitely recommend the White Koji in that case. It is a strain that is perfect for amazake, and its aroma is absolutely great. Light rice would be a fitting strain too.

      Kind regards,

  8. Thank you for taking the time to write this. I’m interested in growing a. oryzae on broad beans to make pixian dou ban jiang (for example, https://chinasichuanfood.com/doubanjiang/).

    Do you have any suggestions with a good strain or strains to try? I’d prefer high protease and low amylase. I’m considering red rice koji, barley koji, soy koji, and soy sauce koji .

    1. Hi Alex!

      Since you are growing the Koji on beans, I would opt for the Soy koji. If you prefer to have as much proetase activity as possible, it might be worth a try to give A. Sojae a chance.

      Kind regards,

  9. Thanks for the advice! I ordered a few and will run parallel experiments to see what takes to the beans and produces the best enzymes. I may try a. sojae next time.

    One other question — do you have any guidance (numbers, intuition, guesses, etc) on how much gas exchange these molds require? I have some synthetic filter disks for mason jars that filter down to 0.3 microns that I use for mushroom spawn production (mostly vegetative growth; fruiting needs way more air), but I’m concerned they limit air exchange too much for a. oryzae even if I grow a fairly small amount per jar. On the plus side, I could steam the beans right in the jar, and do the inoculation in a still air box to keep everything super clean.

    1. I don’t have any numbers, but what I can say is that Koji grows like wildfire :) much faster than mushroom spawn, so I am not sure if it is going to work well in the way you suggested. Koji produces a lot of heat when it grows, so it is better to have it in a thin mat (max. 3-4 cm thick) in a box. The extreme speed of growth also means that you need not worry too much about contamination too much if you work in a cleanly manner. Koji has much more “elbow technique” than fruiting fungi.

  10. Thank you very much for answering my questions. I will optimize to avoid thermogenesis and not worry as much about contamination. I look forward to seeing how it turns out!

    1. I got my spores, and tried out the soy koji, which worked exactly as I hoped on my fava beans. They smell correct and are perfectly fuzzy after just 48 hours, and indeed heat was not a problem once they got started. The next step is a year or so of lacto-fermentation, so it will be some time until I know how the final product turned out, but I feel like starting from spores has been a big improvement to my process, and as you said it has been very easy to get it to grow fast and well.

      Thanks again for the advice, and I look forward to trying some other strains soon.

      1. I am happy to hear that it has worked out :) Thanks for letting me know!

      2. I have started eating the chili bean paste produced in the above comment (using recipe https://www.chinasichuanfood.com/doubanjiang/), and am happy to report that it turned out very well. It needs another year or so of aging to be at its best, but I’m happy with it at 6 months.

        If anyone else wants to try this, I’d recommend the soy koji as Viktor notes above. I also tried barley, red rice koji, and soy sauce koji. None of them were complete failures, but they took longer to grow on the broad beans (especially the soy sauce koji), and I lost some due to bacillus contamination in the meantime. The soy koji grew very quickly. I will try a. sojae as well next time; I did not try it this time.

        One thing I found tricky was getting the moisture right with the beans, typically they were too wet. I found that it helps to soak them NO MORE than 8 hours, and then, immediately after removing them from the steamer, toss them around a bit in a strainer to encourage surface evaporation. This is a similar technique used to the production of grain spawn for mushroom cultivation — fungi are better able to tap into moisture in the substrate than bacteria which rely on the surface.

        Viktor, do you have a preferred recipe for soy sauce? I want to try making that next, with the remainder of the koji I got for this experiment.

        I’m also interested in producing Zhenjiang vinegar, which is a triple fermentation (saccharification with koji -> fermentation with yeast -> acidification with acetobacter). Do you have a suggestion on which strain of koji to try? I was considering the soy sauce koji, but now that I think about it, perhaps one of the strains for making alcohol is a better choice. The end goal is a rich, flavorful vinegar, which makes me think protease, but I need enough amylase to actually produce the alcohol/vinegar.

        1. Hi Alex,
          thanks a lot for the follow up! Interesting stuff. I want to make doubanjiang too this summer :)
          Did you cook the beans or did you steam them? I’m sure steaming would be more forgiving. Ideally in a pressure steamer, to speed up the process.

          I just wrote a new article on how to make soy sauce, but I haven’t released it “officially” since I’ve been wanting to add some photos. You can see it here: https://www.fermentationculture.eu/how-to-make-soy-sauce/
          I’m not sure if I am happy with it yet, the explanation seems a bit convoluted. Please let me know what you think :)

          As for the vinegar, I recommend the Light Rice Koji, it produces both plenty of amylase and protease. Start your Koji at the usual 30°C and once it’s growing, try to keep it at 35°C, this way you will achieve a good balance between amylase and protease (the higher the temp, the more amylase).

          1. The doubanjiang I made is comparably tasty to inexpensive store bought, but it’s only aged ~6 months. I’m hoping it will improve. It definitely has the right flavor, but is a bit sharp and lacking depth in the same way cheaper store bought ones are. I hope you’ll write up your experiments with doubanjiang, especially if you attempt to make one in the Pixian style (without added oil, and aerobic secondary fermentation). The red oil style I made is easier I think.

            I steamed the beans at atmospheric pressure last time. I’ll try 15-20 minutes at pressure next time, and then let them steam off afterward.

            I left feedback on the soy sauce article there. Thank you for sharing it, this is very helpful.

    1. Hi Antia!

      I got your comment, but I could not reply right away, sorry for that.
      For your purpose, the red rice or light rice Koji is good. Probably I would first try the light rice.
      And I do ship to Sweden :)

      Kind regards,

  11. Hi Viktor,

    I never find information about what kind of rice to use, barley and soy beans seems clear as there’s not too many different ones to choose from. But rice.. I mean for mirin they use sweet/glutinous rice but how about the rest, is the koji capable of breaking through the skin of a whole rice grain or not? (could be cooked a bit more in order for it to open more) otherwise what are your suggestions? Just checked in my japanese shop next door: the typical japanese rice (especially organic is quite pricey) so I first wanted to ask for your advice before buying :) thanks already for your feedback/advise! Vanessa

    1. Hi Vanessa!

      I recommend small and round grain rice. I always use the kind that is recommended for rice-pudding (milchreis in german). I never buy Japanese rice, as Italian rice is so near and just as good in my opinion. Originario is a kind of rice that is rather small grained.
      Consensus is that pretty much the only way to make Koji with whole grain rice is to sprout the rice first. I haven’t tried doing that yet to be honest.

    1. Hi Jeremy,
      I don’t have experience with that unfortunately. But if I am unsure of which strain to use, I usually opt for the red rice koji, as it’s a great allrounder.

  12. If I wanted to make sweet potato vinegar, I should use the black? Where do you get yours? How long would you inoculate the potatoes with it before pressing for booze? You inoculate as,you would any other strain…around 86 at high humidity?

    1. Hi John,

      it doesn’t need to be black koji. We had it in the shop, but we decided to stop selling it for various reasons. One of them is that luchuensis is easier to handle while delivering better results. You can also use White Koji or Red Rice Koji. The important part is the amylases, so you can get fermentable sugars for the yeast. All strains will deliver amylase, some more some less. Luchuensis will also produce citric acid – so it is going to have a special sort of acidity in the end when you make the vinegar.

      And yes, humidity is the same.

      Kind regards,

  13. Hello Victor,
    I am totally new to the idea of making Miso. I only thought of it because where I live in Bulgaria I cannot buy miso in jars only silly soups!
    So I got to thinking maybe I can make it at home.
    Yours was the first and last website I looked at. It is really informative. Thank you.
    So the miso I like most is white miso, however being vegan I already consume enough soya so I would like to make miso with chickpeas instead.
    Please advise which would the best koji for this?
    And are there any tips?

    1. Hi Liska!

      For a white miso I recommend the Light Rice Koji. It has been bred for this very purpose :)
      When you make the miso, use 2 parts Koji rice and 1 part cooked chickpeas. I think it’s a good ratio for this type of miso. Add 6-7% salt and wait for 2-4 weeks :)

      Wish you good success!

  14. Thank you Victor for your swift answer!
    Reading back through your other answers I think I understand to use pudding rice for the koji rice.
    Do U send instructions with the packets?
    You write cooked chickpeas, is the rice used raw?
    Apologies for asking questions to which you probably have the answers already in thus website, however the internet here is weak and therefore difficult to browse with!!!
    A friend will be ordering for me V. soon :)

    1. Hi again,

      I don’t send instructions with the packets, I post them here in this blog.
      The rice must be kojified first. Once the mold has grown on the rice you can proceed to make miso with it. Do not cook the koji rice!! You will kill all the enzymes that will break down the proteins and starch of the chickpeas.


  15. Hi Viktor,

    Is barley an OK substrate for A. Sojae? A. Sojae Koji is mentioned in the Noma Guide has an option for making Garum, as it’s high in protease enzymes.


    1. Hi Tony,

      truth to be told, I don’t know. It’d grow for sure, but I can’t really predict how well. You would have to try.

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