We interrupt this programming to undertake a year-long meju doenjang project

Oh look! A SQUIRREL.

I am not one for singular focus. At any point in my life, I’ve a number of sidequests. This is much to the chagrin of anyone waiting for my next book.

These days, my most intricate sidequest involves my most ambitious fermentation project yet: making Korean doenjang from scratch. Which means making meju blocks, comprised of boiled, ground, hand-packed soybeans, and wild fungi. The fungi part is the diciest part. Wild fermentation is—wild!

Meju are the foundation blocks (haha, pun unintended) of doenjang. They’re hard to find and buy (believe me, I’ve tried), and they’re very pungent, so I understand why they’re not in stock anywhere. And yet one must first make (or obtain) meju, which once finished, are then submerged in a saltwater brine (for months) to make doenjang and soy sauce.

The process is one that is a long game. Nothing about it is fast. The whole thing—from boiling soybeans to finished doenjang—takes about a year.

You have to make meju blocks first.

Meju requires the following:

• Soybeans (I used 4 lbs in one round, 5 lbs in another. I get about 1 block for every .75 pound, so even if you have 1 pound of soybeans, you can make 2 smaller blocks, but then your doenjang output will be lower but if you’re in an apartment or don’t have a big onggi you might prefer to use 1 pound of soybeans)

• A heating mat

• Rice straw (or aspergillus sozae / aspergillus oryzae spores)

• Thick kitchen twine

• Something upon which to hang the meju from, whether it is a ceiling hook, or drapery rods, or in my case, a laundry drying rack

• Optional: One of those outdoor fly fans (optional, but I didn’t want a single fly close to my meju).

• Another optional thing: Mesh bags like either nut milk bags or fruit bags in which to put the meju when they hang to (yes, there is a pattern here) keep flies away from the blocks.

These are the steps to make meju:

1. Make blocks (i.e., soak soybeans, boil soybeans, mash soybeans, form into rectangular blocks shaped like bricks).

2. Dry blocks in a warm but not too warm environment, like a heating mat, until they are dry enough to handle without falling apart, 3-5 days.

3. Hang blocks (traditionally with rice straw) to continue drying at room temperature for 6-8 weeks.

4. Ferment blocks: put in a box with lots of rice straw or rice hulls and set atop a heating mat (set so that the temperature is warm but not hot) for about 2 weeks.

5. After they are fermented (by this point, you should have white and/or green and/or yellow and/or brown mold on the blocks), hang them up to dry again as in step 3, for one month.

6. You have meju. You can then use the meju blocks to make doenjang and soy sauce.

There is a lot of waiting involved, as you can see. Meju is a three month-long process. (Doenjang is even longer).

It took two rounds to get a decent set of inoculated meju blocks, and I want to make clear that success isn’t guaranteed out the gate when it comes to fermentation. In the first round, my blocks developed black mold and I had to toss them. Let me show you my miserable failure:

On the 4th day, there was black mold. Black mold bad! TOSSED.

I am all about people sharing their failures. It’s from failures that we learn. And it’s failure that can sometimes inspire. The part of the internet that gets me so down is how everyone tries to make everything look so perfect and easy, when we know that’s absolutely not true.

I went to a writing residency in my early years of writing thinking that I would get there, open my laptop, and start typing endlessly, because that’s what people SAID they did at writing residencies.

And nope. That was not true. I opened my laptop, stared at the screen, realized I was in the middle of nowhere, knew no one, had no one with whom to chat, felt the immensity of my goals, and wanted to crawl out of my own skin. I spent the rest of the time reading, going to the beach, and getting stoned in the woods.

Anyway.

I referenced Maangchi’s recipe for meju blocks—hers is the most step-by-step documented recipe for making doenjang on the written English language web. But there aren’t many recipes out there in general and many that do exist clearly work off her master recipe.

Anyway. This is all to say that the first step of soaking, boiling, mashing, and forming the initial blocks is pretty straightforward, and are pretty much all the same across all recipes.

Here is a video of me making the blocks from the first round (before they became covered in horrible black mold)…This video illustrates “step 1” of making meju: boiling the soybeans, mashing the soybeans, and forming blocks.

But alas, as you know, my blocks formed black mold. FAIL FAIL FAIL.

After throwing the black moldy blocks away, I held off on making another set for a couple of weeks; I was going to have a photo shoot for new author photos at my house, and since meju can get super pungent, I didn’t want to scare the photographer away.

But after the first round failure, I decided more research was necessary on my part.

I bought books. Went deep into my Google search capabilities (yo, I am pretty good at Googling).

Two books were particularly handy:

• Kristen K. Shockey and Christopher Shockey cite Maangchi’s recipe in their book Miso, Tempeh, Natto, & Other Tasty Ferments.

• In Koji Alchemy, Rich Shih and Jeremy Umansky hand the reins over to John Hutt and Irene Yoo, whose process was a handy comparison to Maangchi’s. (Hutt and Yoo provide temperature ranges, but in my opinion, those temperature are a bit high for beneficial fungi—read on to see why).

In the interim, I read up on the science of attracting the right mold for meju. I learned that the following fungi and bacteria are integral in making doenjang, and thrive in the following temperatures:

• Aspergillus oryzae: 86F-95F (can’t go over 95F)

• Aspergillus sojae: 77F-86F

• Bacillus subtilus: 86F-95F

• Rhizopus spp: 86F-98F

• Mucor spp: 68F-86F

• Eurotium: 77F-86F

Other fungi include Lichtheimia, M. griseocyanus, M. mucedo, Murcales spp., Penicillium kaupscinskii, P.lanosum, Scopulariopsis, etc. (Kim, et al., 2013 and Oh, et al., 2024).

I delved deeply into the rabbit hole of the predominant and contributing fungi and bacteria involved in meju development. The bacteria and fungi ebb and flow throughout the process, and there's an entire world of research on the fermentation process (Han et al., 2024).

Bacteria (in addition to Bacillus subtilus there are also Bacillus pumilis, Tetragenococcus, and the ever-wonderful Lactobacillus (the thing that makes kimchi possible)) play a major role, too. According to research, they play a greater role in the steps following meju block formation; doenjang fermentation is largely anaerobic where beneficial bacteria can outgun fungi. And according to that same research, the necessary bacteria largely originate from the dried meju blocks (Woo, et al., 2016).

What do all of these fungi and bacteria even do?

Fungi make enzymes that break down soybeans into flavor compounds (amino acids, sugar, organic acids etc.). Each organism does its own thing with its unique job to add complexity. Rhizopus makes amylase, which produce aromatic esters adding sweet and acidic flavor. Eurotium manifests a woody, earthy, mushroomy flavor in meju. Scopulariopsis also contributes an earthy flavor. Mucor contributes a nutty flavor to soybean ferment.

Some fungi are more important than others; Aspergillus oryzae and Aspergillus sorae are the dominant fungi in meju and are one of the biggest producers of glutamic and aspartic acides, also known as umami. Not only does A. oryzae contribute to flavor, it helps ward off mycotoxins, which keeps your ferment edible (Son, et al., 2023).

WHEW!

Tl;dr the more diverse the organisms on your meju, the better. Each of the fungi and bacteria are doing their work creating and transforming your soybeans into deliciousness.

Something to note: in my first round, I put the blocks on top of my gas stove. My gas stove has a pilot light that keeps the range toasty, even when no flame is turned on. This is where I’ve successfully fermented many things (mostly lactic acid fermentation). So I thought this was the place. But I’d never measured the temperature above the stove.

I obtained an air thermometer. And yes, that area above the stove hovers around 95F, and often exceeds 95F.

I learned, too, that aspergillus niger (aka black mold) has a wide temperature range in which it can grow. But it proliferates at temperatures 95F to 98F.

Dur. So that was the likely source of the black mold outcome. I put the blocks in a temperature range that favored black mold and was hostile to the mold/s I wanted to attract.

(Also, lactobacillus will thrive in temperature up to 113F, which explains why my kimchi was just fine above the stove).

Tl;dr the temperature range to initially dry meju is between 80F and 95F, not to exceed 95F.

So I found a seedling mat for my next round. (I discovered that heating mats meant for humans now have automatic shut offs after two hours: a BUMMER for keeping meju warm). The seedling mat kept the temperature around 85F, perfect for aspergillus oryzae (koji) and bacillus subtilis and all the other good molds.

And that is what I used for my second (and current) round. And yes, I had packets of aspergillus oryzae and sojae spores as inoculation backup.

Look how lovely they are after a few days of drying!

And voila. You’ll see they’re already overcome with white mold, which are A. oryzae and A. sojae.

I also realized that drying them slower and at a more reasonably warm temperature prevents the meju blocks from cracking. So aesthetically, this is very pleasing, too.

Amazing! Now they are hung and will dry for 6-8 weeks at room temperature.

Traditionally, blocks are hung with rice straws that are tied together to allow exposure to aspergillus oryzae and sojae (NOT niger). Other folks tie them up with kitchen twine as I have. My meju are in mesh bags (they’re nut milk bags) to keep flies away (again, I don’t see any flies nearby, but I don’t want any flies near my meju). And because they’re in bags, I’m thinking of going down to Urban Farm Oasis and getting some rice straw to stuff in the bags with the meju for some nice rice straw exposure.

But wait! Why did we just dry them on a seedling mat and then hang them up at room temperature? 100% of the instructions I’ve read include the step of taking them off a heating mat and hanging the blocks up to dry. Why not just keep them on the seedling mat?

I’ve found that the documented steps to making meju are very prescriptive, with not a lot of explanation behind why each step exists. But now that I’ve done some (very cursory) research on the various bacteria and molds required to make meju, I realize that exposing the blocks to a range of temperatures likely attracts a wider variety of fungi. And makes for a more diverse fermentation. Which then ensures a deeper and more complex flavor in your future doenjang.

After this hanging-to-dry step, I’m to put them all in a box with rice straw to do another ferment in a more humid warm environment (again, under 95F).

However, in my second wave of research, I’ve found that not everyone includes the box fermentation step, especially if they’ve inoculated the meju blocks with aspergillus oryzae or sojae spores and/or have some nice mold growing on it already. But I’ll follow that step, even if to get more wild fermentation going with these blocks.

I did a taste test of various artisanal doenjang the other day (omg, maybe that’s another post), and found that there were very mild doenjangs and very funky rich doenjangs. One of the doenjangs even tasted slightly sweet; and my guess is that that particular doenjang was predominantly koji with not a lot of anything else. So I want to give my meju as many opportunities to “catch” the other molds like rhizopus and mucor.

I do know that I’m on the right track, and that feels right. It’s kind of like when you know you’re on the right track with a novel or story. You don’t know the finer points. You don’t know how it will exactly end. But you finally feel you’ll get there.

So it’s me, this meju and doenjang for a year. Maybe by the end, I’ll have doenjang, soy sauce, and a finished novel draft.

Thank you for indulging me this post.