Molding a Future with Koji

Photo by Kirsten K. Shockey

In the first two articles of this series, we introduced Aspergillus oryzae, or koji, in a way we hope has encouraged readers to embark on their own relationships with this amazing mold. After becoming acquainted with the fungus in “Koji: An Ancient Mold and Its Modern Renaissance,” we hope you tried your hand at the Amazake or Shiitake Tasty Paste recipes from “Koji in the Kitchen” to experience some of its secondary ferments. Remember, koji breaks down larger molecules in foods to make them available for use by other microbial fermenting allies. It also enhances and enriches a food’s intrinsic taste. In this third and final installment, we’ll share a recipe for shio koji, a secondary ferment that’s likely to become the secret sauce in your cooking. We’ll also explore additional amazake uses, and dive a little deeper into some of the ways different koji strains are being fine-tuned for exciting new developments in modern cuisine. To wrap it all up, we’ll take a look at what the koji renaissance could mean for food systems as a whole.

Shio Koji

Shio is a common secondary ferment of koji, meaning you need the primary ferment — some type of grain populated with koji — to produce it. Shio is used to amplify expressions of a food’s salty and savory characteristics. Think of it as a soy sauce without the soy notes. It’s typically added to sauces, dressings, and brines, and used to dress cooked vegetables and pickle raw foods. Try drizzling shio over a stir-fry after you’ve removed it from the heat (much like a finishing salt), or use it to brine a piece of fish before poaching or grilling. 

Flickr/305 Seahill

If you make your own shio koji, you’ll find that it starts out looking like rice floating in water, but it finishes looking more like a constituted porridge. This is because the enzymes in koji and the added salt are slowly breaking down the grain that koji used as its substrate. At the end, the shio will be soupier, with fewer discernible grains of rice. You can also put it through a blender to make it smoother and creamier for your sauces and dressings. 

Make your own shio koji using this recipe.

Additional Amazake Applications

Amazake is the sweeter of koji’s secondary ferments. Using it as a base, you can propel into a dizzying array of possibilities. While typical amazake uses include drinking it straight and incorporating it into dressings, brines, wine, sake, and vinegar, the koji renaissance has foodies asking, “What else can amazake do?” Between the variations in the way amazake is produced and the variety of foods to which it can be applied, the possibilities are almost endless.

Getty Images/bonchan

When making amazake, you can manipulate the incubation temperature to make it sweeter or saltier. Higher temperatures (up to 140 degrees Fahrenheit) produce a sweeter product, whereas lower temperatures (as low as 80 degrees) will make it saltier, providing a wide range of amazake applications. Once you’ve experimented with amazake to find what you enjoy, start adding it to sourdough starters and quick bread batters, or pour it over leftover dinner grains to create a probiotic breakfast cereal. It can also be used as a sweetener in baking. It’s similar to brown rice syrup, and will impart complex flavors and give baked treats body, richness, and a moist texture. It’s particularly well-suited for use in scones, muffins, brownies, blondies, rich spice cakes, and some cookies. 

To substitute amazake as a sweetener in a recipe, use 1/4 cup of thick amazake for each tablespoon of sweetener. If you’re replacing a dry sweetener, such as sugar, you’ll also need to remove 3 tablespoons of liquid from the recipe per 1/4 cup of amazake to account for the extra liquid.

Create your own customized amazake with this recipe.  

Other Frontiers 

Through the ages, different strains of Aspergillus emerged as humans applied the mold to new substrates and experimented with its uses. Today, there are dozens of different “seeds,” or starter cultures, used to create specific types of koji. These starter cultures, known as tane in Japanese, are broken down into three families, which are referred to by the color of their spores: yellow, black, and white.

The yellow strains, A. oryzae, are the most readily available koji starters, and are typically grown on light rice, red rice, barley, soybean, and shoyu. The spores of the different A. oryzae strains are all part of the same genus and species, but they have different enzymatic abilities. For example, a soybean koji spore has high protease activity, and so is effective at breaking down the protein in soybeans. However, it’s not nearly as effective at producing amylase enzymes, so it’s not good at breaking down carbohydrates. At the other end of the spectrum, light rice starter has high amylase capabilities, so it eats carbohydrates, but it doesn’t have as much protease and lipase enzyme strength, so it doesn’t break down proteins and fats as well. Despite this, it’s a good beginner koji that can be used for a broad spectrum of applications. Red rice and barley starters have more middle-of-the-road enzymatic capabilities.

Another species gaining popularity outside of Japan is A. luchuensis (also known as A. awamori), one of the three types of black koji. It produces a large amount of citric acid, so it’s less susceptible to bacterial contamination. Traditionally, it’s used to produce the distilled spirit shochu. (A. kawachii, a mutant white strain, is also used to make shochu.) We’ve talked to makers who are getting creative with this koji’s potential and growing it on leftover foods, such as day-old bread, that might otherwise be tossed out.

Any serious koji-maker will benefit from experimenting with different starter cultures to find the one that gives the best results for their specific applications.

More Flavor Controls

Armed with some light rice koji and basic incubation equipment, a novice koji-maker is set to discover the mold’s enzymatic magic for years to come. While different strains produce different flavors, even one koji strain can be manipulated by temperature to an extent to achieve multiple flavors. For example, one might use A. oryzae with both starch and meat substrates, but dial the temperature down when incubating meat to encourage protease enzymes, and dial the temperature up for starches to encourage more amylase enzymes. You can also adjust according to your plans for the end product. For example, if you know you want to make amazake ice cream, plan on incubating koji on a high-starch grain at the higher end of koji’s incubation temperature range (80 to 95 degrees), and produce amazake with a higher ratio of fresh koji-cooked grain. If you’re careful to not over-incubate your amazake, you’ll get a sweeter product that makes a great sugar substitute. Similarly, if you know you want to make shio koji for a fried chicken brine, grow koji at a lower temperature to encourage protease, and you’ll get a heartier translation of flavor when you convert that koji into a shio brine.

In addition to its flavor customization possibilities, koji has shown potential to reduce the salt content of foods during preservation. As such, explorations into koji may have implications for low-salt preservation, and other culinary applications that are currently salt-dependent, though there’s been little widespread testing done so far.


Koji is continually powering new culinary expressions, and given the variation within koji species, enzymatic activities, flavors, and textures, there seems no end to the dimensions we can unlock in foods we think we already understand. For example, if a vegetable grown in poor soil is void of the secondary phytochemicals and phenols that bring it to its highest expression of both health and flavor, the result is a flat and less nutritious vegetable. Perhaps a deeper understanding of the power and potential of mycelia will cause us to mindfully engage and nurture unseen life, such as soil, throughout the natural realm. Koji and its microscopic magic tune us in to the variation and possibility of dynamic life. A respect and wonder for that can emanate, just like mycelia, into the ways we produce and otherwise curate our food.

When you get your hands on koji, begin to experiment — not only with koji’s versatility, but also with different types of food. You’ll find that food with inherently higher expressions of flavor, or food from thriving living soils, provides an even deeper and more complex platform for koji’s inexhaustible subtlety. In this way, koji not only has the ability to push us to the edges of flavor, but it also has the power to keep us searching, evolving, and improving food along the entire supply chain. 

Meredith Leigh and Kirsten K. Shockey are fermentation fanatics. Their expertise spans fermented fruits, beans, vegetables, and meats. They’ve teamed up to spread the gospel funk and the magic of koji whenever possible. Kirsten’s books include Miso, Tempeh, Natto, and Other Tasty Ferments. Meredith is the author of The Ethical Meat Handbook.

Published on Feb 11, 2020
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