Making Koji, Malting

Spent rye grains inoculated with Aspergillus luchuensis and Rhizopus oryzae and other microbes for a sour rye liquid for baking and for brewing. That’s advanced level. Keep reading.

We are having our last #KojiFest2019 event and the first #Zymes2020 event at Fifth Hammer Brewing in Long Island City on December 16th, 2019. You must pre-register for the event.

In the meantime, we will be publishing this 16 part series about how to make koji and extract it’s enzymes, and how to use what the koji is made on – a substrate – directly in brewing or baking or miso or sauce making.

You can also use koji in it’s extracted form as well as a whole substrate such as koji grown on rice to make pickles, sake, shoyu koji, amasake and more.

Please like this post if you do. Feel free to comment or suggest or offer correct. Thanks!

About Enzymes

Enzymes serve two roles. They break down things such as tiny bits of food that you eat into smaller things. Or they combine smaller things like the amino acids from proteins into bigger things. Enzymes make possible every vital function of living things. Sometimes enzymes already exist in living things like your gut.

But most times they are used process things into food or drinks. Without the enzymes in malted barley, for example, it’s unlikely that either bread nor bread would exist as they do today.

Enzymes from koji have been used in European and American food manufacturing for at least 100 years now. We will get into what they have sometimes been combined with (other microbes, yeasts, techniques).

They are very safe to use, but you must be careful when handling them. Anything that can tear through grains or the muscles of animals should not be handled carelessly (see below).

Joichi Takamine

“Curiously enough this tiny and important hustler has scarcely attracted attention in the Occident, and this fact made me determine to work for it’s introduction to industrial use in the United States”

This quote is from a paper printed in 1914 in The Journal of Industrial and Engineering Chemistry (Vol.6, No.10). The author is Jokichi Takamine. He’s talking about koji (A.oryzae).

One of the things he was trying to do was to address the concerns of brewers and maltster – the people that make sprouted grain malt for beer – about the cost of the ingredients to create diastatic enzymes. The price of barley could vary. considerably from season to season. He had earlier filed a patent in the US to do so, “in a process not hitherto practiced”. He succeeded.


On February 23, 1894, a patent was filed in the US : “The object of this invention is to prepare and manufacture diastatic enzyme, or soluble ferment in a concentrated form which possesses the power of transforming starch into’ sugar for use in various industries, by a process not hitherto practiced, and in a very economical and practical manner. 

My invention is based upon the utilization of the property possessed by certain fungi during their growth on proper media of producing diastatic enzyme.

Typically, barley was malted. Malting creates diastatic enzymes. But Takamine thought of using something that was pretty much being thrown away, yet which could produce way more diastatic power and be less perishable. 

Despite some violent outbursts suspected to have come from the maltsters at the time afraid of losing both money and their businesses, the brewing and food manufacturing industries in in the US ultimately adopted the use of enzymes, sometimes malt from barley or other grains for beer, but overwhelmingly from fungal enzymes from Aspergillus in baking, food processing and medicine.

Today both brewing supply houses and enzyme companies sell specific enzymes from many fungus, molds, even bacteria but different types of Aspergillus (koji) are used extensively throughout the world.

Takamine’s substance became an amazingly useful drug used to help people digest food. Enzymes are a very big deal. You can make your own as described below, but be aware that a small microbrewing operation can very quickly become larger than the brewing or refrigeration or heating capacity of your space.

How to Make Takadiastase
  • 5 gallon container
  • 2 1/4 pounds (1024 grams) wheat bran
  • 3 gallons lukewarm water (9000 grams)
  • 1/2 cup (138 grams) coarse 100% NaCl salt
  • Aspergillus oryzae spores (1 gram pure spores)

Taka-Diastase is made with Aspergillus oryzae, the hardest working fungus in the world. It is made on wheat bran. We milled off the bran from winter wheat berries – they have tasty bran, but other types of wheat brans work well – but you can buy it in sizes from one to 50 pounds.

We suggest you start off with 2 and 1/4 pounds (1024 grams) of wheat bran. Remember that wheat bran is unlike wheat berries or even flour. It is typically very light when dry and flies everywhere.

This is especially important when you are about to harvest (or dekoji) your finished Taka-Diastase. Unlike, say, rice koji, you have to consider how to reduce the temperature without fans after a certain point.

As the temperature decreases and it dries out, fans will blow it everywhere. I recommend either using wood that can absorb a lot of water – when you reduce the heat of something the water will either evaporate in the air or soak into whatever it is on.

We often use lots of cloths when making bean or rice koji. Whatever you chose, be prepared to have lots of cloth changes or at least one other wooden to container to transfer the koji into as it dries.

Unless you are going to use it almost as soon as it is finished – we sometimes have a salt brine ready to throw prepared koji into while still warm – you have to dry it out. Otherwise, it will continue to grow.

And a moist pile of amino acids are a feast for all the wild microbes that hang out in the air.

Did any of this seem complicated or overwhelming? Most people don’t ever make their own koji. You can easily buy it. In 35 pound boxes rice koji can be quite reasonably priced.

But if you only want to make a pound or two of koji, it’s cheaper making it yourself. You can also buy the powdered enzymes. But here are basic guidelines to make any type of koji. (Part ii, next post.)

How to Make Koji
  • Prepare the substrate – with wheat bean that means rinsing well and soaking up to 24 hours with salt. If this were rice, you might have to mill it down then let it rest so the grains didn’t break, but this is bran. Sometimes we use lactic acid or vinegar when making beans, but always salt for wheat bran. We use 1/2 cup (138 grams) of coarse sea salt that we thoroughly mix into the soaking bran. We stir the bran frequently from the bottom while soaking, as you would do every day if you were making a soy sauce or amino sauce or even a quick miso. Bran expands differently than grains or beans. It will try to hang out at the top. Keep pushing it down while stirring.
  • Regulate moisture content – anything that you are making koji on, especially dried starch as in rice or other grains, needs to contain enough water (moisture content) so that when steamed it will gelatinize. After soaking you could weigh your bran or whatever. For wheat bran we want a 35% higher weight. Rice? Nowhere near that. 20% is enough. The amount of time you soak is extremely important. With beans you absolutely have to soak and sometimes even change soaking water several times to rid them of their water soluble anti-nutritional factors (phytates, etc.) for 12 or preferably 24 hours. Polished rice for a few hours at most. You want your substrate to absorb water to start the process of changing it’s structure.
  • Dry your substrate. In this case wheat bran. How? We use cloths. Use whatever you like. You could use a dehydrator. We use cloths. Careful of all the bran that will stick to them. And always have strainers on hand when rinsing anything to prevent clogged drains. Again, don’t ever just pour soaking water, unstrained, down a drain. You will regret it.
  • Steam. The reason you soaked, then dried your substrate was to get water into the center so that your starch would be gelatinized. When that happens during steaming the structure does change. It allows the fungus to have a feast on the substrate. Steam your wheat bran for an hour or two. Make sure it gets steamed evenly. With anything we steam we use steaming liners that we roll things around in to ensure even cooking. You want the steam to penetrate the center and get trapped there as it cools down. That’s why boiling can be problematic. Beans are a different deal. Make sure your steaming water does not run out and burn your pot.
  • Dry after steaming. Fungus loves water. Especially surface water. It’s a free lunch. They won’t bother to work for the starches and proteins inside your substrate because why would then when they don’t have to? Put them to work. If you want the enzymes to break down sugars (saccharification) or proteins (proteolysis) you want them to work hard. Otherwise, you’re just wasting substrate while making a weak product.
  • Dry further. Some people will use fans or even a warm oven to dry off their steamed substrate. With wheat bran, again with the cloths. Careful of how you deal with the stuff that gets stuck on the cloths. Again, use strainers. If you intend to wash the cloths afterwards, soak them in a big tub of water that you strain after lifting the cloths out of like you would get the sand off of lettuce leaves or greens. If they are still wet you could first use fans then throw the drier bran into the oven to get the heat back up but then it’s getting a little more complicated. Especially if you don’t have an oven.
  • Choose spores. The golden rule of koji making is 1000:1. That is for every kilo of substrate (wheat, rice, corn, soybeans or grits, potatoes, etc.) you need a gram of koji spores. Sometime you mix different types of spores. The more spores you use the faster it will create a mycelial mat. The more expensive it will be as well. If you have two gallons of cooked, dried off substrate, a half teaspoon of pure spores is fine. Use more if you like and are impatient. Spores mixed with something else rewire at least a teaspoon per two gallons. Follow the instructions on pre-mixed spores.
  • Prepare Spores. Some people like to mix their spores with a filler or extender. It can be corn starch, or ground rice or cassava flour or something popularly toasted to kill of heat intolerant microbes. For Taka-Diastase we usually use a large amount of filler. Bran typically holds water on it’s surface, more so than rice or beans when not overcooked. We will use lots of ground up toasted wheat bran or even some wheat we had milled to adjust the water content and allow us to evenly distribute the spores.
  • Add filler or not. You’ll be changing the cloths or wood pretty often anyway with brans – corn and rice bran koji is made the same way as wheat bran koji – but you really want to get as much water off before hand as possible. Adding a filler allows you to distribute spores more evenly in water substances. With rice or drier beans it’s up to you.
  • Apply Spores. For rice koji, we just dump the spores directly into a bundle of rice when the temperature is around 98F temperature and shake and roll. If your substrate is dry, you don’t need to go into any ritual spore shaking process. You want to disperse the spores as best you can into your substrate. It’s harder if there is too much water. Sometime you have no choice, but that’s advanced koji making. If the substrate is in a nice setting, you can let the entire thing rest a half hour before bundling up.
  • Prepare your temperature for Proteins like beans. If you got caught up on the prepare your setting part it’s because you didn’t prepare it ahead of time. Koji doesn’t not appreciate rudeness. Nobody mistreats baby and gets away with it. Koji can grow from between 80F and 105F. Aim for 90F, and if you hang out at 85F or 95F you’ll be okay. An 85F temp will grow more protein degrading enzymes like proteases for beans, fish, meat and nut based things.
  • Prepare your temperature for Starches like rice or brans. Rice for shio koji or amasake or sake or things that you really care more about creating glucoamylase or amylase or other enzymes to break down starch into simpler sugars like it hotter. 95F is fine. 100F is also fine is you are ready to get the heat down when it starts to take off, usually around 18 hours. At that point all most people will be trying to do is to get the heat below 95F unless they are not using a very precisely controllable heat source. That kojimata territory that involves machines and air vents and fans and sophisticated control techniques that most home koji makers should not have to concern themselves with. Keep it small.
  • Humidity Control. Unless you are making your koji in a rapidly changing environment where it could get really dry quickly, bundling your koji well during it’s first 12 hours is enough. If your substrate is properly dried and most of the water is in the center you don’t have to worry about evaporation or dryness. Home koji makers just bundle their koji up well. We use kitchen safe plastic or thick water resistant cloth to keep the moisture in and protect from drying.
  • Wetness Check. After the first twelve hours and your first redistribution of the koji – you will have to change the cloths for wheat bran or beans or if the koji looks at all wet – unbundle and let a little more air get at your koji. It loves oxygen. Not cold air though. And not wet air. You should notice something going on. It should not look or feel wet. Cover with a very slightly moist towel if you are concerned about drying out. (Part 2 in next post, but before we go:)

The Awesome Power of Koji

There is actually a large body of evidence on why bread and pastry bakers, farmers, and koji growers must be very careful about both inhaling aspergillus spores, as well as getting it on their skin. We will talk about that as well during the year long series, just remember to always wears gloves and masks when dealing with enzymes. 

It makes sense that something with the power to break down meat, fish, or very hard grains would be something to treat with caution. Sometimes things that are obvious to someone working in a professional, including the pharmaceutical industry and food manufacturing industries where Aspergillus and enzymes are used extensively, are not well known or made public.

Please be careful when handling enzymes created by anything, either from a sprouted grain or a fungus. Here are is a very small sample of some of the things that can happen when inhaling spores or enzymes from Aspergillus oryzae. As in the koji we are describing how to make.

  • Valdivieso, R & Subiza, Jose & Hinojosa, Mariel & Carlos, E & Subiza, E. (1994). Baker’s asthma caused by alpha amylase. Annals of allergy. 73. 337-42.  Abstract: Two bakers with bronchial asthma and two with rhinoconjunctivitis are described. Prick and RAST tests were positive with wheat flour in all of them, but the challenge test (nasal or bronchial) with wheat flour extract was positive only in one asthmatic baker. The prick test, RAST, and nasal or bronchial challenge done with alpha amylase extract (a glycolytic enzyme obtained from Aspergillus oryzae and used as a flour additive) were positive in all four patients. Our results support previous data indicating that alpha amylase used in bakeries is an important antigen that could cause respiratory allergy in bakers. It can function as sole causative allergen or in addition with other allergens used in the baking industry.
  • Sharma BB, Singh S, Singh V. Hypersensitivity pneumonitis: the dug-well lung. Allergy Asthma Proc 2013;34:e59–64.
  • Gerfaud-Valentin M, Reboux G, Traclet J, et al. Occupational hypersensitivity pneumonitis in a baker: a new cause. Chest 2014;145:856–8.

RSVPs for this event are this Saturday. You must go to the Eventbrite link to register. There are limited spaces left for this event. 


Taking Stock of and Making Stock from Sweet Corn

First the corn stock. You can actually make this with half eaten, older, or cosmetically challenged corn and it will still deliver the smell and taste we lust after in corn. If you are using fresh corn save the husks for making tempeh or tamales or little packets of natto if you like.

Roasting corn picked a little more than a few days ago to create a very tasty stock and water replacement to give dishes a greater organoleptic corn thrill. The smell of corn roasting until brown from the Maillard reaction and the caramelization of corn’s inherently large percentage of sugars can provoke a Proustian Madeleine response in those of us that grew up near corn fields.

Corn Stock Recipe

Hack up four ears of raw, sweet corn into two to three inch pieces after shucking and removing the corn silk if it’s still on, then place in an un oiled pan. Bake the corn for 3 or 4 hours.

You could also just brown the pieces very well in a big heavy pot until they were caramelized and dark but not burnt. Or throw them on a hot grill.

Cover with water (6 to 8 cups) and cook for an hour or two on top of the stove, or cook in a pressure cooker – we’re not naming names here – in the same amount of water for 20 minutes. Let cool off and strain. You can also add any well roasted corn kernels to the broth – up to 1/4 cup per 6 cups of water, and strain everything for a richer taste.

Besides using this for our corn misos, breads, rice or bean based breads like idlis and dosas, you can just chill the stock and sweeten it (or not) for iced tea. Or add spices and tea for chai. Use it instead of water or even stock in just about any case you would use water or stock.

Of course you can also use it as a chilled or hot soup base adding whatever you like to it. In any case, this stock is so versatile and tasty and simple consider it as part of your mise-en-place. It lasts for up to a week in the refrigerator. We make it once a day when it’s corn season.

The amount of starch in corn and that starches ability to be gelatinized makes it a stand out candidate for microbial intervention: pickle it, ferment it, use it instead of rice starch for a kimchi or fermentation base, or turn it into a soy sauce type seasoning agent and dipping sauce. Or a marinade. Or alcohol. Or mirin.

Lots of recipes coming, many presented at one or more of September events we are presenting at, or collaborating with other people and groups to provide.

Just a few of the things you can make with corn:

  • wine
  • pickles
  • puddings
  • cakes
  • breads
  • chutneys
  • soy sauce (with or without beans)
  • grits
  • hominy
  • polenta
  • moonshine
  • beer
  • corn nuts
  • syrup
  • flour
  • sprouts
  • tamales
  • tortillas
  • tacos
  • stews
  • mirin
  • ice cream
  • and many, many different types of desserts.
Corn germ and corn tips from nixtamalized corn. In the 1980’s we used to make macrobiotic unrefined corn germ oil and barley malt pecan pies with a cornmeal crust. Not exactly low fat but unbelievably tasty. The removal of the 
germ reduces the chances that the corn will go bad in your larder or when transported to other places.

If you’ve ever picked the corn tips off newly nixtamalized corn (whole dried dent or field corn treated with potash or more commonly calcium hydroxide or cal) to make pericarp free, homogenized color, hominy it’s easy to see how canned hominy of a very consistent quality, or dried hominy (known as posole by most people) became popular.

A lot of the quality of fresh corn that is available to most consumers depends on how close a local corn field was, and how carefully and coldly fresh picked corn could be transferred to an alert buying public.

Except for a few hard core corn enthusiasts that argued about the perfect timing schemes to seize ears of corn from the fields and throw them into boiling water to get the sweetest, freshest corn, suburban and city folk were pretty much stuck with buying corn from grocery stores. Removing the kernels off the cob and getting just the juicy parts to be sauteed as a vegetable side dish is always a treat. Some places sell fresh, raw corn kernels as well.

For a while, popcorn was the best selling gourmet food item in any state in the country. As you’ll see, it makes a mean sprout that can then be popped, nixtamilized and made into a variety of things such as miso.

You can do a wide variety of things with dried (or freeze dried) sweet corn and field corn. There’s nothing like breaking out a big jar of pickled corn still on the cob or corn relish or chutney in the middle of winter. Our corn miso will make you think you are eating a piece of freshly grilled and buttered corn. Even if you are eating it on an ear of fresh corn in the summer.

Sweet corn miso aging in the refrigerator after a 6 month fermentation period. Deep.

We suggest adding some some at the last minute as is recommended with all misos – boiling it destroys the good things about this ferment and dulls the flavor – to a new England Corn Chowder, or spread on a corn based pizza crust topped with roasted garlic, cheese and pickled, charred jalapeños. Yes, recipe on the way.

Corn on the cob is just unavoidable in certain areas. No clam bake or crawdad boil or lobster dinner or barbeque was without corn. Often steamed along with the other ingredients, or cooked straight in salted butter and served as a side with unsweetened corn bread that had been cooked in cast iron in ashes, or dumped right on top of a shrimp gumbo.

Also, the argument about how to best (read properly and socially acceptable) eat corn in public, and whether it was even fair to serve something sure to get stuck in the teeth of well heeled diners made corn on the cob something avoided at formal dining occasions.

Corn from Masienda we nixtamalized and spiced and added to roasted pumpkin seeds and other ingredients for tempeh using a culture called Rhizopus oryzae. For hominy for our tempeh – or posole – we never use more than 1% lime (by weight). Same way we make our rapid grits for fermentation after soaking out the corn bran as we call it.

A Few Corn Facts

In most areas there are typically two classes of corn sometimes with a few varieties available, sweet corn or field corn. There are other types of corn grown for specific reasons, but most people never see them growing.

Sweet corn is not supposed to dry in the fields if it is meant to be eaten as sweet corn. Racoons and other corn eaters like coatimundi would never let that happen, anyway. Pumpkins with prickly vines, pole beans and tall sweet corn can be an effective deterrent. As can dogs.

Field corn was always yellower, grew taller, left on the cob to somewhat dry out for easier processing like a lot of grains, and a lot of fun to play in. When field corn is really dry it has indents or recessions on the top that are created as the corn loses moisture.

That’s also why it was sometimes called dent corn. If you get it before it is that dry it’s edible and tasty, just not as sweet and juicy as sweet corn.

But all corn is good. Big thanks to the Mississippians and other Native America tribes that created entire societies in what is now called the United States around corn. Pretty sure Vermont would be just green mountains had corn not been amenable to the cold climate there.