Shio Koji (塩麹)

Shio Koji (塩麹)

Whenever I have the opportunity to talk about my latest culinary projects, I always try to showcase my dishes in the best linguistic light. Words like creamy, unctuous, crispy and fresh, when used opportunely and parsimoniously, can conjure saliva in previously dry places and maybe an occasional stomach rumble.

Certain foods are, at first glance, less amenable to exultation. Maybe they’re visually unappealing, have a texture repudiated by the adjectives in the English language, or exude a perfume that could be likened to old shoes only euphemistically.

Yes, I’m talking about you. (Valdeon Cheese by Artizone, licensed under CC 2.0)

Of course, it’s all on the tongue, and in the nose, of the beholder. Personally, if I hear the words “old shoe” at the cheesemonger’s, I get a little giddy. One could posit, in this case, that the eulogies, like the foods themselves, are an acquired taste.

Such is the case with one of my recent discoveries, a Japanese fermentation called shio koji, which has become a staple in my kitchen and the object of many delicious experiments.

Magical Mystery Mold

“What’s shio koji?” I inevitably get asked.

“It’s a bacterial fermentation of dried mouldy rice” I say, nodding enthusiastically.

Judging by the slight permutations in their facial expressions, my listeners don’t seem all too convinced. Maybe I ought to refine my elevator pitch. Clearly, most people don’t get as excited at the mention of bacteria, yeasts and molds in the kitchen as I do.

It’s not like its appearance is particularly appetizing either. White specks suspended in a buttermilk-coloured liquid, it looks more like soggy porridge — something you might spoon-feed to a 3-month–old rather than the secret sauce for culinary magic.

And yet culinary magic it is.  Thanks to an abundance of proteases and amylases, shio koji is ideal for tenderizing, marinating, fermenting. Its umami characteristics are perfect for enhancing the flavours of just about any dish, from desserts to vegetables, and it’s full of gut-friendly microorganisms. So far, I’ve had great success using it to marinate fish and seafood, to dress up vegetables, and in place of salt in a variety of dips and sauces.

Why Would I Want to Eat Mouldy Rice?

Well, I hate to break it to you, but chances are, you already have. And you loved it.

Let’s start at the beginning. Koji (麹) is the Japanese name for a type of mold — aspergillus oryae (ass-per-GILE-us o-RYE-zee) that we are indebted to for the production of foods such as shoyu (soy sauce), miso (soybean paste), mirin, rice vinegar and sake. See, told you!

Aspergillus Oryzae up close

Basically, we owe to koji the whole arsenal of foodstuffs that make Japanese cuisine the epitome of umami, and in turn, make it no surprise that our word for the sixth taste is a Japanese one.

Diving Deeper

Historians have traced back the practice of fermentation with Koji to China, roughly 3000 years ago for the predecessor of miso paste, in which grains are inoculated with koji and used as a substrate for the fermentation of other foodstuffs (such as soybeans), and around 2000 years ago for the predecessor of shoyu, in which the soybeans themselves are inoculated with koji. Records from the other side of the Japan Sea tell us that both these practices had been introduced to Japan by 700 AD, where they developed over the following centuries into the aforementioned arsenal of products that characterize Japanese cuisine.

Fermentation involving koji may have started in China, but it was in Japan that this wonderful microorganism was first isolated, grown, and sold as a starter, allowing for the mass-production of miso, shoyu and sake. This process of discovery is, like many great inventions, a testament to human curiosity and ingenuity, and to the serendipity that makes life particularly delightful to those who are willing to accept it.

As Takeo Koizumi, zymologist and professor at the Tokyo University of Agriculture, explains:

“It is amazing to think that nearly one thousand years ago, tane koji [isolated koji spores] makers were clever enough to cultivate pure tane koji using ash, then market it as a starter under the same name to soy-sauce manufacturers, miso manufacturers and sake brewers. Nowhere else in the world at this time could you find anyone able to isolate and purify microorganisms, let alone market them as an individual commodity. One can only marvel at the extraordinary depth of knowledge of the Japanese people at that time. Judging by the fact that those involved were no doubt aware of the “anti-bacterial powers” of ash when they used it to isolate and purify tane koji, it might be accurate to consider the Japanese as the first people to purify and isolate microorganisms.”

An illustration from the Koueki Kokusankou, an agricultural book of from the Edo era (1603-1867), showing soybeans being added to fermented wheat for the production of shoyu (say sauce). Reproduced from Koizumi (n.d.).

This is quite remarkable considering that history commonly attributes the discovery of microorganisms to Anton van Leeuwenhoek, a Dutch lens-maker who devised the first microscope in 1673, at least a few centuries later.

Shio koji is a quick ferment, in which rice koji (米麹 ), steamed rice inoculated with koji spores is mixed with salt and water, creating an environment for anaerobic lacto-fermentation to occur.  The end product, is a salty, umami, slightly-sweet, enzyme-rich porridge that can tenderize meats, enhance flavours and dress up dishes. Your imagination is the limit.

But don’t take my word for it. Give soggy, mouldy rice a chance, and then delight in creating nasty eulogies to discompose the uninitiated.

Making Shio Koji at Home

Making shio koji at home could not be easier. It requires three ingredients and an initial effort of about five minutes (strenuous, I know). After the initial mixture has been combined, you will need to stir it once a day for the length of the fermentation (7 to 10 days), after which you can stick it in the fridge and forget about it until you need it.

I use a rough ratio of —  4 rice koji : 1 salt : 5 water.

Since the containers I buy at my local Japanese grocery usually contain around 300g of rice koji, the numbers below are based on that.

References

Fukushima, D. (1985). Fermented vegetable protein and related foods of Japan and China. Food Reviews International, 1(1), 149-209. doi:10.1080/87559128509540768

Koizumi, T. (n.d.). Traditional Japanese Foods and the Mystery of Fermentation [PDF]. Kikkoman Corporation.

Guidance and Inspiration

Just One Cookbook — How to make Shio Koji

Nordic Lab — Shio-Koji

❤ Thank you Josh and Nami!