How To Make Ama-Koji (Sweet Koji) For Great Gut Health

Written by Sharon Flynn
Meet The Japanese Sugar Replacement That Heals Your Gut (No, Really)

Photo by Susan Brooks-Dammann

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You’re already familiar with sauerkraut and kimchee and kombucha, I’m sure. But have you heard about this ferment that will add a gorgeously sweet tone wherever you need it?

Ama-koji is the most wonderful sweetener. It looks like a nut milk, but It’s actually almost painfully sweet to eat or drink alone (although plenty of people do, and it can easily be diluted to suit your palate). In winter, it’s best to drink warm, and I recommend chilling it in the summer for a lovely, nourishing sweet fix. Like all fermented food, ama-koji has distinct probiotics that help to populate and soothe your gut.

It's also used regularly as a sweetener. The sweetness comes purely from the starch in the rice and the reaction to the koji converting those starches to glucose. Koji is Japan’s national fungus, responsible for converting soybeans to miso, tamari, soy sauce, and rice into sake and rice vinegar. In the case of ama-koji, it creates a digestive enzyme that converts the starch to glucose. Let it sit longer and that glucose will attract yeasts that will create some alcohol. Leave that even longer and you’ll have some rice vinegar. Fermentation is great like that (I go into depth about many different types and ways of fermenting things in my new book, Ferment For Good). When using it in chai tea, you essentially use the ama-koji as the milk and sweetener. This is great for the dairy-free person in our home. You can also try it as a kind of ice cream—blend the ama-koji with 200 mL (7 fluid ounces) of extra water until smooth, add cocoa powder or cacao powder to taste, then freeze or put into your ice-cream maker.

Ama-Koji (Sweet Koji)

Gluten-, dairy-, and sugar-free

Preparation time: 1 hour

Fermentation time: overnight

Equipment: food-grade thermometer, rice cooker (or slow cooker)


  • 200 g (7 oz) rice (see notes)
  • 200 g (7 oz) rice koji (available at Whole Foods and Asian grocery stores—it comes in white blocks frozen, or dried in tubs)
  • 200 mL (7 fl. oz.) water


  1. First, cook the rice, then cool to at least 60°C (140°F). Crumble in the rice koji, add the extra 200 mL (7 fl oz) water, and stir to combine.
  2. At this stage you want to keep it at a constant temperature of about 60°C (140°F). I achieve that by keeping the rice cooker on the "warm" setting with the lid ajar but with a tea (dish) towel over the top. You can also easily do this with a slow cooker set to 60°C (140°F), or with the oven on low. Open it up to give it a stir now and then in the first hour or two. I usually leave it like this overnight and then awake to a beautiful aroma.
  3. It will keep for about a week—heat before eating each time. It may change somewhat and become less sweet as it keeps fermenting, even in the fridge. To keep it stable, and the flavor and enzymes intact, you can store it in the freezer for up to 6 months. Thaw before using.

Notes: Short-grain rice produces a very sweet drink, and medium-grain less sweet. Combine the two for a happy medium, or make it with all short-grain if you intend to use it as a sweetener in your chai, for example.

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