Meet Koji, Your New Favorite Fungus

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Let's check out this pork chat.

I'm not sure anybody other than you, maybe, has been so excited about eating a fungi-crusted piece of meat ever.

Right?

All right.

Oh, my gosh.

Go for it.

Oh, my god.

Nice, isn't it?

Wow.

No, you are not tuning into an episode of Bizarre Foods, but that was the sound of Cynthia eating a moldy pork chop.

And it was quite possibly the most delicious pork chop I've ever eaten.

It was covered with a microbe called koji.

Now, if you're Japanese or you're just into all things Japanese, you might be nodding your head right now.

Koji is like an old friend to you.

Although, maybe you weren't expecting to encounter it on a pork chop.

And for everyone else, meet your new obsession.

Okay, my new obsession.

But until recently, I only knew Koji through one of its end products, Miso.

If you're not familiar with Miso, it's a salty, umami-rich fermented bean paste that's used to make, you know, the Miso soup you might order at a Japanese restaurant.

So what is Koji and how does it transform food?

Plus, how did it become Japan's national fungus?

And where is it popping up in the US today?

All your koji questions, the ones you never knew you had, they'll be answered this week on Gastropod, the podcast that looks at food through the lens of science and history.

I'm Cynthia Kraeber.

And I am Nicola Twilley.

And before we head off on our microbial adventures, I know, I know we're obsessed with microbes.

We need to tell you that this episode of Gastropod is made possible in part with funding from Science News, your source for surprising and important science reporting.

This week, scientists learned that Saturn's icy moon Enceladus packs snacks suitable for microbial life.

And a new study suggests that taking artificial trans fats off the menu reduces hospitalizations for heart attack and stroke.

Discover science for foodies and everyone else at sciencenews.org/slash gastropod.

Okay, my name is Mariko Grady.

I'm Japanese.

Mariko was born in Japan and lived there for 30 years, but she met her husband in San Francisco and she ended up moving to the Bay Area.

And after I got a baby, I want to share my Japanese food with my family.

Mariko now produces and sells traditional and slightly less traditional Japanese foods around the Bay Area.

She sells koji, yes, it's a mold, and she sells products that you can make with koji, different types of miso, for instance.

Koji is

kind of

microorganism.

So without koji, we cannot make sake, soy sauce, miso, meading.

Every Japanese product is basically koji.

So key ingredients of Japanese fermented food.

Koji is key.

Mariko kept telling us.

Very worldwide famous.

So this fermentation product, we can create a lot of umami flavor.

So without koji, we cannot create a Japanese umami.

It really does help Japanese cooks make everything, soy sauce and sake and miso and mirin.

It's impossible to imagine Japanese food without it.

Koji products may be most important.

So, yes, without koji, we cannot make basic Japanese cuisine.

Yeah, I believe it's

national fungus.

It really is the national fungus.

In Japan, there's a special day devoted to it, October 12th, National Fungus Day.

One of the country's most popular manga is, yes, pretty much all about Koji.

It's called Moya Shimon, Tales of Agri-Culture, and the hero is a kid who can see microbes with his naked eye.

Koji is a super cute little yellow golf ball with five little wiggly antenna-type things.

It looks a lot like a little asterisk.

There's an entire comic book line and video series and even products, cell phone charms and stickers and Lego kits and earrings, all of this little Koji character, a microbe.

Maybe, Cynthia, we are not the most most obsessed after all.

There's some serious competition out there.

But maybe Koji really does have some superpowers because how does one microbe end up helping us produce all of these amazing, delicious foods?

Of course, we called up our resident microbiologist, Ben Wolf of Tufts University, to find out how it works.

It's really a lot like a rotting log in a forest, where all molds and filamentous fungi, and even the things that make mushrooms, they all make a living by secreting enzymes.

And they secrete enzymes that are sort of really important for degrading their environment.

In the case of Koji, it's not on a log.

In fact, it's usually on steamed rice.

Its scientific name is Aspergillus arisi, which makes it a member of the Aspergillus family.

Aspergillus, the genus, is just like super good at producing enzymes, so they actually use it industrially

to make enzymes for like food processing and detergents and stuff like that.

That's Arielle Johnson.

She's head of the new open Fermentation Lab at MIT's Media Lab.

But she got her start with Koji playing in the RD kitchens at NOMA in Copenhagen.

A quick note about how this all works.

First, Koji is sprinkled onto partially or fully cooked rice, and Koji loves that environment.

And the mold grows and grows, and as it grows and breaks down the rice, it releases all the enzymes that Ben and Arielle were talking about.

As Arielle said, this is kind of the secret to Aspergillus' superpowers.

Then it's time for step two.

You take the koji-covered rice with all of those awesome enzymes and you mix it into something else.

Soybeans for miso, soybeans and roasted wheat for soy sauce, more rice to make sake,

and then you leave it to get on and ferment some more.

So it's a two-step fermentation.

The koji grows on the rice, then all those enzymes break down another product like soybeans.

And as they do that, they also free up sugars for still more microbes to help out with that secondary fermentation.

I mean, I think it's a really amazing transformational tool.

and I mean if you've ever made misu before and tasted it like when you pack it into the vat it tastes like salty refried beans.

It's not an exciting I mean soybeans are nice.

They're tasty beans but it's salty beans.

But then the thing that it turns into even after a few weeks is like perfumed and golden and succulent and sticky and delicious.

Some of those magical enzymes are amylases, which break down starch into sugars.

Some are lipases which break down large fat molecules to smaller ones.

So that's like what happens when you dry age meat.

And some are proteases, which break down protein.

And you're also getting like a big punch of free amino acids.

And especially glutamate is very umami-potent.

So

the more that the proteins break down, the more of that that you'll get, and the more like delicious, I want to eat more of this flavor.

So Koji is completely transforming the flavor and texture of the final product.

It's also freeing up sugars for some other microbes to help out with the fermentation, including our old friend yeast, and those other microbes are adding their own flavors to the mix.

And then of course koji has its own flavor, which it's also bringing to the flavor party.

Banana, it's it's kind of sweet smell.

Or if you eat this koji rice,

it's like

chestnut.

Yeah, some sweet flavor.

That spell that you're talking about, it's like

flowers crossed with mushrooms, I would say.

So I smelled and even tasted koji on its own.

To me, koji smells like a slightly funky grapefruit.

It's insanely addictive.

I wanted to keep sniffing it all day.

I wanted to bury myself in a mound of koji.

But you had a podcast to make instead.

Seriously, though, that addictive, delicious, sweet smell, that's probably the reason Koji and humans first became friends.

Remember how koji first needs to grow on steamed rice?

That's likely how humans first met met Aspergillus orisae thousands of years ago in Asia.

At least that's what John Gibbons thinks.

By accident, some spores floating around somewhere, right, are contaminating some newly steamed rice.

It has this sweet smell, right?

And people are drawn to it because it smells good.

And if you let it ferment a little longer, some wild sacromyces are probably going to find its way into that as well, right?

And then you have a very sweet-smelling, sweet-tasting, alcoholic beverage.

It always comes back to booze.

John is assistant professor of biology at Clark University and he has made it his mission to use genetics to unravel the story of Koji.

So you start by looking at its family, Aspergillus.

They're a super super diverse collection of species.

So they look very similar.

If you look at them under a microscope, they look very similar.

Their morphology is very similar.

But they span the evolutionary distance of humans and fish.

And they're kind of the, we call them the Dr.

Jekyll and Mr.

Hyde of fungi.

We've been telling you about the Dr.

Jekyll varieties.

These are the nice guys, the delicious ones that make great food for us.

But, and here's where Aspergillus is bizarre.

Then there's this evil, nasty Mr.

Hyde.

Almost all Aspergillus varieties can actually even kill us.

So these fungi and this Aspergillus are famous for it produce these really nasty defense chemicals, coral secondary metabolites.

They make these chemicals to keep other microbes away from their food.

But some of them are super toxic to us, too.

So how did we domesticate koji and help the microbe get rid of its Mr.

Hyde side entirely?

Yeah, well, so the good stuff we think started maybe about 8,000 years ago, 6,000 years ago, something like that.

So there's this famous paper that showed from some pottery shards from, you know, about 6,000 years ago that what was in that pot was very similar to what is what we consider sake.

And you can't make sake without having the the fungi present first.

Did I already say it all comes back to booze?

It all comes back to booze.

But so we know that by then this one particular strain of Aspergillus had emerged that was all good news, no bad news.

But how?

John looked at Orizae's closest relative, it's Aspergillus flavus, and it produces a really nasty toxin called aflatoxin.

You might have heard of it spoiling batches of peanut butter, but Aspergillus orisi, its toxin-making genes, have been totally turned off.

John thinks this was probably originally a random mutation, but then we humans responded to it with enthusiasm.

We picked it out, we gave it a nice comfy home with all the steamed rice it could eat, which helped it reproduce until that mutation became standard.

So what that's telling us is that it's not putting its energy into producing defense chemicals.

So why not?

Well, it doesn't need them, right?

To actually produce these things, it costs a ton, a ton of energy.

And by disabling these genes, they're not putting the energy into that.

They can put it into primary metabolism, right?

So we're giving them this perfect environment.

They have this delicious rice that they can always eat, right?

There is never any competitors, right?

Because we're not introducing any other bacteria or fungi.

So it doesn't need to produce these defense chemicals.

John thinks this is how we domesticated koji.

We found the right mutations and kept encouraging them to grow.

No more Mr.

Hyde.

In fact, Koji just keeps getting nicer over time.

So one of the other big genetic changes that happened after the loss of toxicity was there's a gene called alpha amylase.

So alpha amylase is the key enzyme that's used to break down starches.

So, all strains of Aspergillus flavus, the wild one, have a single copy of alpha amylase.

Now, when you start looking into Orizae, every single strain that you look at has at least two copies that are identical, and some of them have more, three or four copies.

So, the more copies you have, the more of that you can actually produce.

And the more of that enzyme you can produce, the better you are at breaking down starch and rice into sugars.

But, what's still weird, Koji hasn't actually split that far from its poisonous relative.

It is is still so closely related to flavus that they should be considered one species.

I can totally see this being a plot point in the manga.

You never know when a microbe's evil cousin will strike.

Dun dun dun.

But back in reality, after these mutations where it lost the toxicity and turned into the hardest working microbe in town, koji became increasingly central to Asian cuisine.

After people in Asia discovered that their moldy, grapefruity-smelling steamed rice could turn into booze, they figured out new ways to use it.

Koji-fermented soy sauce and bean paste, for instance, both developed early on in Japanese and Chinese cuisine.

From there, you know, you can see from the 13th and 15th century in China, there are advertisements that are selling what's called Moyashi.

This is koji, right?

So before we even knew, you know, five, six, seven hundred years ago, before we knew what microorganisms were, we were selling them.

Back in the lab, John is trying to repeat this evolutionary process to check whether his theory about how we domesticated koji is right.

And so, what we're doing is we're trying to mimic the early sake-making process.

And we have a few different isolates of Aspergillus flavus that we have been propagating continually every generation on rice.

And we're up to about 30 generations now.

But we are going to leave John there because we don't have time for evolutionary processes to play out on a podcast.

Meanwhile, back in Japan, a whole specialized industry grew up around koji.

Seed koji dealing became a family business.

The knowledge about how to grow happy koji was handed down from father to son and kept strictly secret.

And just as the koji business itself became highly specialized, so did making products with it.

There are very specific methods.

The temperature koji grows in affects the enzymes it produces.

And this is important.

If you're making miso, you want more of those protein-destroying enzymes.

If you're making sake, you want extra enzymes that turn rice starch into sugar because yeasts love sugar.

And so these methods and techniques to arrive at the right blend of enzymes in your koji, these have been developed and codified over centuries in Japan.

The exact thickness of the straw layer that is used as insulation, the exact number of hours in between each time you turn over the koji-covered rice to aerate it, All of it is a rigid formula.

And this long history and tradition and knowledge is one of the reasons you have such a delicious variety of, say, misos and sakes in Japan.

Koji basically helped create Japanese cuisine, but how did Koji make its way across the ocean to the US?

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I've got two people for you, Cynthia.

Joan Bennett and the man she is obsessed with, Jokichi Takamini.

I think he is a really interesting and somewhat overlooked figure in the history of biotechnology.

Joan is a big deal microbiologist at Rutgers University.

She's also past president of the American Society for Microbiology.

Joan became obsessed with a Japanese guy who lived in the 1800s because of a strange coincidence.

Here's the first thing that happened.

Given that I had a double major in history when I was young, I decided as part of the review article I would put together a table which I almost called, and I maybe even did call, great moments in the history of Aspergillus, in which I collected dates in which some member of this large sprawling fungal genus had contributed to something in the history of microbiology.

And so putting together this table, I find that the first patented fungal enzyme is from Aspergillus orisi.

And the guy who filed that patent in 1891 is our story's hero Takameni.

Not only is this the first patented fungal enzyme, it's quite likely the very first biotech patent in the U.S.

at all.

So Joan publishes her paper with its cool table of great moments in the history of Aspergillus.

And then...

So about six months later, I am in the Tulane Medical School library.

So I see this book, very narrow, little thin book, Jay Takamani.

I said, what is there?

A whole book about this obscure patent holder.

So I pull the book off the shelves and I take it out of the library.

It was a thin vanity biography that Mrs.

Takamani had done for him after he died.

And it's not a very good book, but the story is so terrific.

It's a crazy story.

The story that Mrs.

Takamene had written about her husband in this vanity biography.

It describes this Japanese man coming of age during the time when Japan had first opened to the West, how the government had sent him to Edinburgh to learn about Western technology.

He learns English, then his government sends him to a

World Fair in New Orleans in 1884, where he meets, falls in love, and eventually marries a blonde, blue-eyed, pretty good family girl from New Orleans.

And in those days, that's an interracial marriage.

It was very unusual for a Japanese from a wealthy family to marry a Westerner.

Takameni brought his bride back to Japan, and his family was not super impressed, nor was his bride.

She hated life in 1880s Japan.

So they came back to the States.

The thing we haven't told you yet is that his family was a sake-making family, so Takameni was quite familiar with Koji's activities.

He thought Koji might help with digestion, because at the time there was this idea that indigestion was caused by eating too much starch.

And he takes his Koji enzyme and patents it and turns it into a digestive aid, something called taka diastase or takadiastase,

which is apparently still available in Japan as I usually describe it.

It was the alka-seltzer of the 1890s.

Takameni and his wife had been living in poverty in Chicago.

But this digestive aid thing, that's a brilliant move.

And Takameni is not done with koji yet.

He recognized that this fungal process, the koji process used in Japan, was akin to malting enzyme.

When you're making alcohol, you need to turn your grain, whatever it is, into sugar, because yeast can't ferment starch.

And so for yeast to make an alcoholic beverage out of a starchy substance, something has to intervene.

And we have traditionally used malt, which is germinated grain.

And in Asia, they've used fungi, filamentous fungi, which are much faster and more efficient.

What a fantastic idea.

Takamini wants to speed up whiskey making using koji.

Sounds great, right?

Well, maybe it would have been, but an inconvenient fire to the distillery got in the way of his whiskey business.

Mrs.

Takamini described arson as burning down a whiskey plant that Takamini was involved in.

I don't think it was arson, just whatever it was, but there are some aspects to the story that are somewhat murky.

It might not have been arson, but like Joan said, things definitely got murky.

It's easy to imagine some of the forces arrayed against him.

There is definitely a question about what went on in Peoria

and why

things went down so poorly there.

Seeing Takamini's later career and what a truly brilliant businessman he was, I suspect some of the issues there had to do with his powerful intellect and

apparently just native knack for business up against some Midwestern Protestant American

early capitalists in this whiskey business who excluded him because he was so foreign.

Takameni really was a brilliant businessman and scientist.

He even isolated adrenaline, and he had a huge monopoly on aluminum.

He and his wife became very rich.

But his major passion was trying to bridge the divide between East and West.

And he had grown up in an era when it was all about Japan absorbing Western culture.

And he was constantly looking for ways for his own culture to inform the West.

Takameni held tea salons.

He even apparently paid for the cherry trees that are around the tidal basin in D.C.

as a symbol of peace.

And he worked very hard for peace between the two countries.

You know, he would have been heartbroken by World War II because he tried so hard to build political understanding.

So the Koji was an example of this in practice.

But unfortunately, his attempt to transform America through Koji was lost.

There were early examples of people making soy sauce and miso here, so Koji certainly had shown up, but it hasn't been well known, not like in Japan.

And neither has Takameni.

That's the sad thing, that he's not well remembered in either of his countries because of this two-country thing.

And he might be better remembered in the United States if it hadn't been for World War II.

A man who had worked all his life for understanding between the countries, and he died in the 1920s.

Many of his things were

You all probably know how poorly the Japanese were treated in the U.S.

during World War II internment camps, so it's not a surprise that traces of Takameni and his achievements were destroyed.

You can find some of his belongings, though, at a museum in Kanazawa in Japan.

Joan has made the pilgrimage.

But despite the sad end to the Takameni story, like Cynthia said, Koji has been in the U.S.

for more than a century now.

But it's mostly been used by Japanese Americans to make Japanese products.

No wild whiskey-making experiments after Takamani.

At least, not for a hundred years.

Until now.

Today, Americans, mostly chefs, are experimenting with Koji in all sorts of weird ways.

The magazine Cook Science sent me out to Cleveland to meet one of them for a story.

I have Tourettes.

I was actually born a cripple.

I didn't walk without braces till about six-ish.

So I had kind of a lot of like personal adversity as a kid.

Jeremy Umansky is a chef in Cleveland, and he grew up there, too.

Education for me was always a bit difficult.

So I really got into self-education just at a young age.

Self-education, meaning reading the encyclopedia from cover to cover.

After my mom realized that I would just sit there and literally from A to Z, from page one to the end of every volume, like read them straight through and then cycle back and just do the same thing again.

My family members started going to garage sales and that sort of thing.

At that time, encyclopedias came out yearly editions, and people would buy a new edition every year and then sell the old one.

So he ended up with piles and piles of encyclopedias, all of which he read cover to cover again and again.

So, one, Jeremy is obsessive.

Two, he has a background in food.

So, my grandmother was a kosher cater here here in Cleveland.

I started working for her lightly when I was about 10.

By the time my bar mitzvah rolled around, I was working for her almost every weekend.

And

I really started to get into food.

And not just blinces and brisket, but bugs.

Jeremy started cooking crickets and mealworms for his family in his teens, way before eating bugs was cool.

In short, this is not your typical upbringing, and Jeremy has not followed your typical life path.

Jeremy eventually became a chef, and then he and his wife moved back to Cleveland, and he started working in a high-end restaurant called Trentina.

The chef there, Jonathan Sawyer, asked him to make miso out of chickpeas.

Jeremy learned that to do so, he had to use koji.

I mean I was very familiar with all the foods made that you need koji to make.

And I thought I was familiar with how those foods were made, except I didn't know what koji was.

So Jeremy does what anyone would do.

He goes online and he googles koji and then he orders some.

And it comes with a 15-page booklet all about how to grow this fungus correctly.

And Jeremy, being a self-taught sort of dude, had already studied mushrooms and growing them.

And he thought a 15-page process seemed a bit over the top.

So I kind of realized that I could probably, I could probably hack this Koji thing straight up.

The first thing he did was throw out the idea that you need specially steamed rice for Koji.

He figured the microbe just wants food, and at the restaurant, they had lots of overcooked waste rice for making soup.

Perfect home for Koji, and it worked.

And then Jeremy fell in love, like everyone seems to, with the smell.

One sniff, and his heart belonged to Koji.

I can't think of a better word than intoxicating to describe it.

Straight up.

I mean, it is, it's intoxicating, it's bewitching, it's captivating.

How many times do you hear people describe an aroma with those words?

Like,

it grabs you.

As you might imagine from hearing about his early life, Jeremy's imagination quickly ran wild.

That smell kind of reminded him of the sweetness of scallops.

So he's like, would it be possible to grow koji on rice flour dusted on scallops?

That sounds like a great idea, until you remember koji is from the tropics in Asia, and it needs a humid, warm environment to grow, which would usually be death to a scallop.

So I said, you know, if I could hold this at 80 degrees and it not spoil, I might be on to something cool.

So he tries it.

Which I mean, leaving seafood at 80 degrees for 36 hours?

It's freaking me out even thinking about it.

This is not going to end well, right?

So I got to the restaurant early that day,

probably like six in the morning, just because I was like excited to check on this.

And I cut one open and it smelled fine.

And the texture was great.

No flies laid eggs on it.

And

there were no of the classical signs of apparent spoilage.

Like the smell wasn't off.

The color wasn't off.

I probably licked it knowing me.

you know, just to see if there was any, you know, ammonia or anything that developed that would lead me to believe that it could potentially have spoiled.

None of that was there and it smelled incredible.

And so he cooked it up and tasted it and fed it to the other chefs.

And it was delicious.

The texture firmed up and it almost developed a texture more leaning towards chicken.

The koji crust cooked up beautifully and I hadn't seen anything that said don't eat the koji.

Like I just assume people eat koji.

Yeah, no.

People don't eat koji crusts like this.

And just to be clear, there is absolutely nothing traditional about this.

People do not grow koji on rice flour, dusted fish, or meat to cure it, and then eat seafood with a koji crust.

As far as I can tell, Jeremy is the first person to have done anything like this.

And live to tell the tale.

And the exciting thing is, all those enzymes created by the koji, they transformed that scallop.

They gave it an entirely new flavor and texture, something different from anything Jeremy had tasted before.

The flavor was just incredible.

It had cheesy notes and yeasty notes and fruity notes and ocean, like scallop sweetness, and

a little bit of like ocean air brininess to it.

Like

nobody had ever tasted a scallop like that.

And it had like a crust on it that was the Mayard reaction on steroids, you know, because it had this mycelial mat that we cooked up.

So it acted like a breading, essentially.

After this, Jeremy went nuts with Koji.

If Koji had grown into a delicious breading on a scallop, then what about breading for fried chicken?

He grew out koji on chicken and fried that up.

Of course, it was delicious.

Then he started growing it on other meats, like the pork chop I ate, which, by the way, I'm still dreaming about.

Oh my god.

And then he forgot about a piece of meat that he was growing koji on in the walk-in, and it kept curing for a week and dried out and turned into a delicious piece of charcuterie way faster than the traditional Western methods, which I also ate.

It was also delicious.

So I started specifically culturing whatever I could from lamb tenderloins to pieces of chicken to beef to llama to, I mean, anything we could get our hands on.

And I would just hang him in the walk-in.

And then we had a full, like, whole muscle meat from every animal you could think of in-house charcuterie program that we could do koji with.

All of this he's eating and then serving to customers.

Yeah, we put it on the tasting menu like right away.

We all ate a bunch of the koji.

We waited like a day or so.

Everybody felt fine.

Just to say it again, Japanese people love koji.

They have koji phone charms.

Japanese cuisine is not possible without koji.

It's the national freaking fungus.

But nobody in Japan, at least as far as we know, would even dream of making prosciutto with koji.

But it worked.

And it opened up this whole new world of textures and flavors.

So that's exciting.

And I ate it.

It is really delicious.

But microbiologist Ben Wolf is not so sure this is such an awesome idea.

So the reason no one's ever done this before is it defies biology in many ways.

So it makes sense that no one would have really successfully done this in the past because you normally would age meats for these kinds of processes at lower temperatures.

So you never really could get aspergillus to grow.

Meat is usually cured at below 50 degrees.

Koji has to grow at around 80 degrees.

If you're keeping meat at those temperatures for days at a time, without koji, it will almost always spoil.

Jeremy says that Koji is crowding out all the other microbes, but Ben's not sure.

He says other microbes might be able to get in there even with the Koji mat around the meat, and even if you cook the meat, the toxins could stick around.

That actually is slightly problematic.

Ben says he'd like to see more research.

Jeremy agrees he does not want to make anyone sick.

And Jeremy actually can't legally sell that Koji-cured meat, though he can give away tastes for free, which he's done.

So he's working with local health authorities to figure this Koji business out.

It all needs more research.

Charcuterie aside, although Jeremy is definitely a little crazy, he is not alone.

Across America, chefs are starting to see the potential of Koji, not just to create these delicious new flavors, but also to help cut down on food waste.

Our goal always is to find a way to minimize the amount of kind of loss and things that we're putting into the bin.

Nikki and I visited Kevin Fink at his restaurant Emmer and Rye in Austin on a busy night.

We were in town with Pop-Up magazine.

Kevin, like Jeremy, is also kind of obsessed with koji.

This is a theme.

Once you discover koji, you just keep diving deeper.

Kevin uses it throughout his dishes in ways that are definitely within health codes.

For us, Kevin put out a platter of all sorts of weird and wonderful condiments he'd created by combining kitchen leftovers with koji.

Like, for example, a bread-based soy sauce.

Then there was this amazing condiment of, seriously, crab shells and dried lamb.

Amazing.

He also wanted some help using up egg whites left over from pasta making and his colleague Jason White put Koji to fermenting the protein-rich egg whites.

You ended up pureeing the actual like koji berries in it.

It gives this like extreme nuttiness that you don't have in traditional kind of like more water-based models.

So this sauce was literally just egg whites with the koji rice blended in and left to ferment and I was ladling it into my mouth by the teaspoon.

It was the best, creamiest, saltiest, most umami sauce in the world.

Kevin's used koji in ice cream and in cookies.

He's made butternut squash miso.

Kevin's testing koji out like Jeremy is.

To American chefs, koji is an incredible new kitchen toy that they're still learning how to play with.

But it doesn't mean it's always going to work, and we're for sure not 100%

and knowledgeable and things like that because as much as we are understanding of that, we're not scientists and we're not working in a lab.

So we're in many ways testing on ourselves.

And then if it's successful, then later on on others.

This is exactly Arielle's point too.

All these experimental new uses for Koji, they're super exciting and a lot of them are actually totally within health code.

But they just need more experimentation and repetition.

If you think of a like traditional recipe, you know, even if it's something that was developed for a cookbook, it's still something that have had like millions of man hours or usually woman hours of development leading to that.

So some of these things that like we've just started trying with, there's a lot more trial and error that you're gonna experience.

Chefs are making bread with koji.

They're mixing it into ricotta to ferment it into a funky, almost parmesan.

And Jeremy and Kevin and other chefs aren't ignoring traditional uses either.

They're using Japanese koji-based marinades called shiokoji and amazaki to marinate all kinds of meat and fish.

Basically, Jeremy doesn't cook any protein these days without marinating it in Shiokoji or Amazaki first.

And this is something you can try at home if you're intrigued.

Shiokoji is for sale at some Whole Foods, Amazon, all the usual suspects.

I tried marinating fish at home with Shiokoji twice.

Once the fish was mind-blowing.

Once I fucked it up.

Hey, if you're willing to experiment, you can be a part of the future.

Arielle is putting plans for an open-source Koji incubator online.

We'll have links at gastropod.com.

The idea is to start gathering crowdsourced data about how all the different temperature variables and moisture variables and pH variables affect the mold growth and the resulting flavor.

So once we have these incubators going, we're hoping to,

well, we're going to do a lot of fermentation with a lot of different parameters, grow a lot of koji, make a lot of miso with it, and measure as many parameters as we can, and then share that with anyone who wants to read a lot of data.

Arielle and Kevin and Jeremy and a handful of other chefs around the country, they really think that koji could be the next big thing.

Once other people get a whiff of that absolutely intoxicating, grapefruity, mushroomy smell, they too are going to be obsessed.

It's crazy.

So, you know, people are getting into like Koji.

They're kind of understanding it.

And there's lots of online community springing up, like investigating it.

And I feel that, you know, whether it's in the next year or whether it's in the next 10 years, like this is going to blow up.

I really, and not like in my face.

I think it's really that we're going to see a lot of people become just as fascinated with the process as I am and start to explore it and use it in their restaurants, in their butcher shops, in their markets.

Guys, you heard it here first.

This episode, we want to thank some of our supreme Patreon donors.

That's people who give $10 per episode on Patreon.

Muffy Fulton, Katie Kissel, Christoph Ruprecht, Camilla Greer, Sarge Fisher, Stuart Pollock.

We cannot thank you enough for your generosity in helping to keep Gastropod going.

Thanks to Mariko Grady, Jeremy Umansky, Joan Bennett, Kevin Fink, Ariel Johnson, Ben Wolf, and John Gibbons.

We have links to their restaurants and research on our website, and it's all totally worth checking out.

Thanks also to Cook Science, where I first wrote about Koji.

Find it all, gastropod.com.

And see if you can score yourself some Koji.

We want to hear what you think.

We're back in two weeks with something that will be much more familiar to most of us, though some people do find it scary.

Butter.

Till then.

You're basking on a beach in the Bahamas.

Now you're journeying through the jade forests of Japan.

Now you're there for your alma mater's epic win.

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Womp, womp.

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