Koji Propagation




Introduction: Koji Propagation

Koji can be purchased online or in asain markets. but it known to be best when used fresh, which clearly sitting in a plastic bag for weeks on a store shelf does not ensure freshness.

Or if you buy it online from amazon, it comes in an ordinary package, shipped without insulation or cooling in the back of a mail truck for days... also sub satisfactory in the freshness category.

So in search of a way to brew sake at home, I found my options for imported koji to be less than satisfactory... it was also rather expensive! amazon has it for $15/200g. most of that weight is the rice the koji was inoculated into!

This instructable is here to help those homebrewers to get the best quality Koji available to them, even in remote locations where 98% of the people you meet would never know even what "Koji" is, or what it's used for...

Step 1: Little Background Information

Koji is a mold, scientific name of Aspergillus oryzae. This mold is inoculated into rice, and then let to mold over.

Once you have a solid block of infected rice, while it is still white, you can then either use it immediately or refrigerate as is to keep it fresh for a few weeks, or even dry it, then freeze it in containers to keep it fresh for nearly a year! it's been used to make Sake, Miso, and Soy Sauce for hundreds of years. And it's also known to be a great marinate ingredient for all sorts of foods.

while it is possible to buy koji, then mix it with prepared rice to get more koji from your original purchased source, my suggested method and the one we will be walking thru together here is starting from Koji-kin, powdered spores of Aspergillus oryzae

Step 2: What Your Going to Need

These are merely suggestions and guidelines. my backwoods approach is not nearly as good as what a commercial operation is going to create with lab-style sanitary conditions and temperature control. But seeing as this has been done LONG BEFORE refrigeration and even electricity, i'm going to trust that it can do what it needs without too much scientific process.
  • Rice of preference ( enough to satisfy your immediate requirements, this batch is made with 6cups of rice)
  • Koji-kin (2g per Kg/8 cups of rice)
  • cheesecloth
  • steaming pot
  • thermometer
  • food safe sanitary containers to inoculate in
  • insulated box (suggested but optional)
  • sanitary solution (i use star-San sanitizer)

The rice can be white, brown, short, long, etc. But short grain highly polished sushi rice is supposed to be best. just note that the hulls of brown rice stop the fungi from infecting the core, and you will need to de-husk the brown grain rice so that ii is atleast partially broken or scratched

The Koji-kin can be sourced online if you have no local sources. a 1Lb brick of koji-kin can make a whopping 200kg/440 lbs of rice, barley, or soybeans. and is reportedly good for 6-12months from time of shipment if properly cared for (dark, cool location like your fridge).

Step 3: Day 1

  1. rinse with rice water till the runoff is no longer milky white. we want as much of the small particulate matter washed away. if using brown rice remember to Hull it first
  2. Immerse the rice in water, cover, and let it soak for 18hrs in the fridge, or 12hrs if room temp.
  3. Steam the rice, 45min or till "al-dente"
  4. let the rice cool, breaking up the clumps with clean, sanitized hands.
  5. once the rice is 100F, spread out in a thin layer and evenly disperse the Koji-kin over the Rice. this stuff is a fine dust, be careful to not let it blow away!
  6. using some strength, mix this all together and place into the food safe container. I use ceramic crocks and jars, but zip lock bags or turkey basting bags would work just as well if you wrapped the rice in cheese cloth to maintain high humidity levels.
  7. Since it's summer, i just cover the jars and set them in the sun, then just bring them in and put them in an insulated box at night. the more technically inclined folks can choose to put the filled and covered container into an insulated box and turn on a low heat source (Edison style bulb). mist some water into the container to help maintain a humid atmosphere
  8. maintain temp as much as possible between 86-104F closer to 104 will give more sugars and temps closer to 86 will give more amino acids. For Sake, we need those sugars. 110 is too high and your going to need to mix it up to bring that temp down.
  • this is your Zero hour. Know it well...

Step 4: Day 2

  • if your rice starts to go >109F, remove, stir, repack, and expect a solid 20F drop in temp from mixing.
  • As the mold grows, it creates it's own heat. This is noticeable at ~hr20 from inoculation. if it didn't start getting warmer than the ambient temp by now, something went wrong and you should look back thru your notes, or more simply start over.
  • at the 38hr mark, start lowering the humidity (open the box, stop misting the interior) this signals the flowering stage and urges the mold to penetrate as deeply into the rice grains as possible.

at 48hr mark your koji can be harvested, or it can continue for up to 55-60hrs. if it starts to turn yellowish, finish it. that means it's about to turn to spore, which is not the desired state of the mold for fermentation purposes.

Step 5: Finishing the Koji

You now need to finish the Koji. Do so by breaking it up into small pieces, almost granular in nature which is now good for:

  1. Immediate use
  2. Immediate refrigeration for use within the next 10 days
  3. Immediate freezing for use within the next month
  4. drying into small clumps/individual grains for long term freezer storage. (less than a year)
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Native Son Koji
Native Son Koji

4 months ago

Couple of observations, we're a koji producer and regularly make various koji's including barley. We just finished a barley run. (pictures on our Instagram @_broken_mold) We soak for 12 hrs, drain for 1+hrs, steam for about an hour till the white core is gone. We finished this batch in less than 40 hours.

About encouraging folks to produce or propagate their own spores or koji kin. We and other professionals STRONGLY ADVISE AGAINST advocating or encouraging the practice of propagating your own spores (koji kin) as it is UNSAFE and can be DANGEROUS. This is due to a very real probability of cross contamination with other molds common in pretty much all households.

Worth noting, there are only about 10 producers in Japan that produce spores commercially in a "clean room" environment consisting of full tyvek suits, hoods, masks, gloves & booties, air lock transfer doors, air knifes, HEPA filtered air and rigorous lab testing for potential contamination, safety and QC. These are also very highly regulated, again for safety standards. NONE of the larger commercial customers, e.g., soy sauce, miso, sake manufacturers etc., make their own spores, Even though, it may, save money. Why?, it's just NOT safe or worth the risk. AND spores are really not expensive, so why bother? Makes NO sense, and is irresponsible to promote an unsafe practice to anyone, especially, novices.


Reply 3 months ago

the quest for knowledge is often riddled with danger and exhilaration. i appreciate your concerns and will edit the instructable to remove that statement.


1 year ago

As a test I tried rice flour to make my kome kuji. microwaved it in hot water. This is 3 days sitting over a heating pad on the lowest setting with a wet paper towel and a plastic cover. it was a whiter white than the race then spored suddenly on the last day. Im a little intimidated by how aggressive it looks!


Reply 1 year ago

Nooooo.... I hope you didn't use that. It's not at all how kome koji should look.


Reply 1 year ago

I threw it out. It looked like it was going to take on sentience and take over.


2 years ago

the sensitivity of the mold is epic. the tolerances are slim...


Reply 1 year ago

Indeed, it is, and they are. In Japan, there are people who's sole job is to babysit the koji round the clock. This is a DIY project that pays off only if you pay extreme attention to detail.


1 year ago

Hi.Ive summarised a Koji method..could anyone tell me if this is correct, please?
Koji/Kome-koji/rice koji= fresh/fermented grains or rice upto 48hrs then fridge 12 hrs to halt fermentation. Pack and possibly keep in fridge further couple days
Tane-koji/spored whole grains or strained powder = Kome-koji fermented further 36hrs, with no refrigeration process, (total 84hrs) + two days drying, to create Tani-koji grains/spores powder


1 year ago

Hi im looking at doing this Koji and have been compiling a doc for my own reference, from many sources etc. Could the author or anyone in the know have a quick read and se if ive got it correct please. Would be appreciated as im getting confused with the terms etc


means rice). Koji or Kome
Koji, is steamed rice that has had Koji mold

onto it and then incubated for 40-50

used in the production of various fermented drinks and foodstuffs,
and is made by growing the useful mould koji
rice, barley, soy beans or other grains.

is the actual mold.
The scientific name of this magical mold is Aspergillus

refers to powdered
of Koji-kin.


Makes 1.1 kilograms

500 grams pearl barley

Koji tane (koji spores; see recipe
for details)

Koji matures in less than 2 days in
optimal conditions. Those conditions are very specific, but very
achievable, even at home.

Equipment Notes

A perforated half-gastro/hotel pan
(32 × 26 centimeters / 12½ × 10 inches) is ideal for this amount
of koji. Any smaller, and there won’t be enough room for air to
circulate around the grains. It can help to grow koji on clean cotton
kitchen towels that will soak up excess moisture. And finally, as
with handling many sensitive microbes, wearing latex or nitrile
gloves will help keep things sanitary.

One final note: This recipe will
work just as well with
japonica (short-grain)
rice, if you’d like to make a more traditional koji.

In-Depth Instructions

A little bit goes a long way. A
100-gram bag contains enough spores to inoculate 100 kilograms of
grains. It’s also an investment you only really need to make once,
because once you’ve made your own koji, you can grow your own
spores from it for future use (see “Harvesting
Your Own Spores
”). Both versions of koji tane can be used to
inoculate fresh koji. (Don’t worry about inoculating barley
with spores grown on rice, or vice versa; koji’s an equal
opportunity consumer.)

To begin, place the barley in a
large bowl and fill it with cold water. Agitate the grains with your
hand, then pour off the cloudy water. Repeat once more, then fill up
the bowl with water for a third time, bringing the water line above
the barley by a few centimeters. Allow the barley to soak for at
least 4 hours at room temperature, or overnight in the fridge.

Once the barley has soaked, drain
and rinse the grains in a colander until the water runs clear. Shake
off any excess.

The ideal medium for Aspergillus’s growth is on hydrated but
fully separate and relatively plump grains. Boiling can easily
overhydrate them, leaving them wet and mushy. The mold can grow too
quickly in this situation, reaching its reproductive cycle before
producing the concentration of enzymes we’re seeking. If the grains
are very wet, the spores will effectively drown and never start
growing. Steaming allows the grains to fully cook without taking on
excess water. At Noma, we have combination ovens that allow you to
add steam to a convection cooking cycle—they’re brilliant for
steaming grains—but a classic steamer will also work just fine, as
will a sieve or colander set into a pot with a lid.

If using a regular steamer:
Cook the grains for about 20 minutes over simmering water, but begin
testing at 15 minutes. Bite into a kernel—a properly cooked one
should still be dense but easy to chew and should not be hard or
white at its center.

While the barley is cooking, ready
the tray in which you’ll be fermenting the koji. make sure it’s
washed and sanitized. Line the metal or plastic tray with a towel. If
it’s a kitchen towel, make sure it’s clean (and was washed
without perfumed detergent), sanitized with steam, and wrung dry.

Once the barley is steamed, you want
to break it up while it’s still warm so that any residual starch
doesn’t set and clump the grains together. Wearing two pairs of
latex or nitrile gloves will protect your hands from the heat. Rub
the grains between your hands into your fermenting tray. Don’t
apply so much pressure that it ruptures the grains; keeping them
whole is ideal for koji’s growth. Spread the grains out and allow
them to cool to 30°C/86°F on a cooling rack on the counter. Feel
free to fan the grains if you’re impatient. With the grains
steamed, separated, and cooled, it’s time to inoculate.

If using powdered spores: Put a small
amount of the powder into a tea strainer and gently tap it over the
grains. The spores are extremely potent—1 teaspoon contains more
than a billion spores, plenty to inoculate one tray of barley.
Wearing gloves, fold the barley thoroughly, being sure to get into
the corners, and then give it another pass with the spores. Turn the
grains once more, and you’re set.

Spread the inoculated barley in an even layer, pulling it in
from the sides of the tray to avoid creating any spots without access
to airflow. Cover with a clean, barely damp kitchen towel, making
sure there are no exposed areas.

Transfer the tray to your
fermentation chamber. Raise the tray off the bottom of the chamber
with a trivet or wire rack to allow for airflow all around the koji.
In any chamber that’s smaller than a broom closet, keep the lid
or door open
just a crack to allow fresh oxygen in and excess
heat to escape. We saw the mold suffocate all too many times in the
early days of our koji-growing at the restaurant. Insert a
thermometer probe into the bed of barley, and be sure your humidity
meter is running.

No matter what setup you’re using,
keeping tabs on the temperature of the grains is paramount to your
koji’s success. At room temperature, the koji’s growth will be
severely retarded and the organisms will struggle to take root. But
any hotter than 42°C/108°F and you’ll cook them to death.
Humidity also has to be monitored carefully. It’s easy to drown the
koji if the environment gets too wet. On the other hand, should the
grains dry out, the hyphae will meet too much resis-tance and fail to
penetrate the starch. Insert the temperature probe into the grains
and set the temperature controller for 30°C/86°F. Keep the
humidity between 70% and 75% for the duration of the ferment.

Assuming all goes well, after 24
you should notice the first inklings of mold growth: wispy,
ill-defined white threads should begin to cover the barley, lightly
binding the grains together. Remove the koji from the incubator and
set it on a clean rack on a countertop. Again wearing gloves, break
up the grains in the same manner as when they were first cooked.
Mixing the grains brings koji growing at the bottom of the tray into
contact with air and breaks up the mycelium, encouraging further
growth as it tries to spread its web.

After you’ve turned the grains and
broken up any clumps, furrow the grains into three rows, like mounds
in a farmer’s field. This creates more surface area for contact
with fresh air and improved heat dissipation.

After the first 24 hours of
growth, koji’s metabolism will kick into overdrive. Your job is to
keep it alive for the next 24 hours. Return the koji to the
fermentation chamber, with the thermometer probe in the center of the
middle mound. If you notice the heat spiking, adjust the temperature
controller, and open the door or lid for 30 minutes to allow the
chamber to cool down. If you’re worried the koji is still on the
path to overheating, breaking it up again will help to lower the

Over the next 12 hours, the koji’s
mycelium will firmly bind the grains of barley together, forming a
dense cake. By hour 36, the koji will be covered in a light
green or white fuzz
(depending on the strain of Aspergillus
you’re using), but full enzyme production and flavor won’t
develop until hours 44 to 48. At that point, the smell of the
koji should be intensely fruity, like ripe apricot.

To harvest your
koji-kome/rice koji, you need to halt its
. Place the entire tray in the fridge for 12 hours to
cool down
. You can then pack it into airtight containers to store
in the fridge for a couple of days if you have plans to use it in the
near future. We actually find that koji’s flavor improves
considerably after a couple of days in the fridge. It’s perfectly
ready to use as soon as you harvest it, but the refrigerator will
arrest the koji’s growth while the enzymes continue to work,
sweetening the koji even more in the process. If you don’t have
plans to use it immediately, koji stores well in airtight containers
in the freezer for up to 3 months.

To harvest
koji-tani spores/soporated

Make a batch of koji and use gloved
hands to break up the grains onto a sanitized, nonreactive,
nonperforated tray. The mycelium will be very strong by hour 48,
so you may have to pry the grains apart. Do your best to avoid
crushing the barley. Spread the grains out in a single layer to
create the maximum amount of surface area for the koji to sprout its
spores. Cover with a lightly dampened towel and return the koji to
the fermentation chamber. Allow it to grow for another 36 hours.
Continue to monitor the temperature and humidity, but you won’t
need to do any more turning of the grains.

After 36 hours (84 total),
you should see fluffy white, green, or yellow spores,
depending on which strain of Aspergillus you purchased. If
you touch the grains (wearing sterile gloves), your finger should
come away covered in powder. If agitated, the grains will emit a
plume of dusty spores with a strong, almost meaty scent. If grown
properly, the spores should be plentiful.

You’ll need to dry the grains to
keep the spores shelf-stable and to prevent them from becoming
infected by other microbes. Remove the towel that was covering the
koji and the humidity source from your chamber, and dry off any
moisture from the walls. Crack the lid or door a little wider than
when you were growing the koji, in order to increase airflow and
place the sporulated grains in the chamber to dry until completely
hard, about 2 days.

Pack the dried koji (grains whole
or sieved powder)
into an airtight container and store in a dark
cupboard for up to 6 months or freeze for longer-term storage.







have now made the fermented KOJI KOME(rice or barley) or if desired
your Koji Tane (dried spores for further culture powder))



extra dried koji tane spores for more culture in future

koji/kome koji to



can use shio koji to marinate meats, make pickles, flavor your
vegetables or use it as a salt substitute.

or within

sichuan fermented Doubanjiang
| Broad Bean Paste


the sticky rice element of this use Kome
koji or
Sticky Rice (Jiu Niang)












Question 2 years ago on Step 3

Hi, thanks for your post, It's very easy to follow. I just have a doubt.
I just bought dehydrated koji rice wich I'm going to hydrate soon for making miso. I couldn't find koji kin at Argentina so I'll try to make this koji kin myself following your steps so I can make many miso batches in the future.
My doubt is: to propagate this koji rice I've bought, do I need to let it spore as in step 6 and then mix this green rice with fresh rice? or should I hydrate this rice and sprinkle it in fresh rice?
Thank you very much!


3 years ago

Hi, thanks so much for this! I find your instructions much more clear than many others out there.

When making the rice, can you elaborate slightly on when to gauge proper doneness? Also for the spore production roughly what temps and humidity have you found for success?

Thanks again!


Reply 3 years ago

To produce spores I left the koji rice in a cooler about 10 days without more humidity neither more heat, until it ended growing, after that I put it in a plate, inside my oven (I did not used the oven on those days, it was used because it is dry and dark, not for heat) to dry. I used some of those greenish, yellowish fermented dry rice to make Koji rice again some days ago, it worked!


3 years ago

It worked. I will upload pictures tonight. On December I did some koji rice, I did it using a cooler. Once the rice was white and fluffy, about 3 days, I used most of it to make miso paste, then I saved about 3 or 4 tablespoons of that rice in the same cooler. I left it there about 10 days or so, until it was dry. During the fermentation process it changed from white up to green, yellowish, etc. After that I put it to dry inside my oven. 3 days ago I cracked a few of it, then I mixed it with steamed rice, the rice is white and fluffy as the one I did on December with store bought Koji-kin, I am happy as getting Koji-kin in Mexico is way too complicated.


3 years ago

Hello, thank you so much for sharing this knowledge! I'm following your tutorial right now. As I have a really hard time for getting the koji kin, I plan to follow step 6. I have the following questions:

How long can I save/store the kojied (a new verb, the grains infected with koji) rice grains?

If I steam 1 kg of rice, how many grams of kojied rice could I use for it so it can get properly infected?

Thanks in advance!

Btw, your Mario shirt is amazing! I played that game back in early 90's in my NES console!


4 years ago

Worth noting that the glass gar expiriment failed. As suspected, a damp, warm, dark place is the best case to grow mold cultures