The following is an excerpt from Koji Alchemy: Rediscovering the Magic of Mold-Based Fermentation by Jeremy Umansky and Rich Shih.

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Amazake serves as the base for sake and other rice-based alcohols (and by fermented extension, rice vinegar) but is also a star in its own right. Its roots can be traced to early alcohols made from fruits, honey, koji, and rice in regions of what is now known as China. The Nihon Shoki, a text written in 720 CE, makes mention of amanotamuznake, which has been referred to as an early amazake. There are many reasons why amazake has been a staple in homes for so many years; it’s the base for most Asian styles of alcohol and liquor, it is transformative when applied to foods in the kitchen, and it’s wholesome and delicious.

When we first started working with koji, amazake was the food that really opened our eyes to the limitless possibilities that koji affords us in the kitchen. It has all the sensually intoxicating elements that fresh koji does, plus it has more versatility and goes further in terms of usability. Over the course of many years, we have used it to do everything from culturing cream, to making butter, to acting as the hydration element in breads and pastries. But the biggest asset that amazake has compared with other koji-derived foods, aside from its enzymes, is that it isn’t seasoned with salt. Shio koji, by contrast, is salted and, in our opinion, is therefore slightly less useful. As culinary professionals we want to control the salt in our foods as strictly as possible, and sometimes we don’t want salt at all—this is exactly why amazake is our basic go-to in the kitchen. Another benefit that amazake provides is that it is optimized leveraging amylase over protease and for specific applications such as creating sweet treats and confections.

Classically, amazake is made at room temperature and is ready in two to three days. It is a simple combination of cooked starch (traditionally rice or barley), inoculated starch, and water. The cooked starch can be anything from rice to nixtamalized corn, and this holds true for the inoculated starch, too. These ingredients are mixed together and left to be broken down by the amylase enzymes created by the koji, typically at ambient room temperature left uncovered. To accelerate the process, you can set a jar or container in a warm-water bath, easily done with an immersion circulator.

During our early explorations we realized that different styles of amazake could be made to suit different purposes. For example, we made a very watery amazake that we would let sit out and slightly sour for a few days with the aid of our little bacteria friends Lactobacillus. This soured amazake proved excellent in applications as diverse as a finishing seasoning drizzled over a plate to a court bouillon alternative when poaching seafood. This sour amazake also works well in dressings, marinades, compression techniques, and a host of other preparations that call for flavorful liquids.

On the other hand, you can make the traditional-style sweet amazake by using half the amount of water used for the sour type. This amazake makes for a great stand-alone treat but can also be used to marinate meat or even be puréed smooth and spun in an ice cream maker to yield a delicious sorbet.

Whether sweet or sour, the uses for amazake are numerous. You are free to use whichever one you want for whatever application you see fit.

For koji applications in general, amylase has optimal activity between 131°F (55°C) and 140°F (60°C) to break down starch into sugar. Although there is a much wider range of factors to optimize, we’ve found that this works quite well across the board. While simply mixing the ingredients for amazake and letting it sit at room temperature will work just fine, you can accelerate the process by holding it at temperature. This is especially helpful if you want to make a very sweet base for alcohol and vinegar. As you will experience, there are distinct differences between an amazake that is made at ambient temperature and one that’s precisely heated.

It’s the base for most Asian styles of alcohol and liquor, it is transformative when applied to foods in the kitchen, and it’s wholesome and delicious.

One thing to keep in mind when using a temperature-controlled device is that these systems aren’t perfect. As the chamber/bath/oven is heating, it may overshoot what you’ve set it to. How much this deviates from your target temperature is specific to the system you’re using. To understand how much variation there is, we recommend that you use a supplemental temperature probe to track the temperature. Short of that, setting your system to be on the low side, 131°F (55°C), should work fine. When working to maximize protease enzyme activity for amino acids (umami), the same range of 131°F (55°C) and 140°F (60°C) applies.

Ambient amazake can and will develop sour notes due to contamination from beneficial lactic-acid-producing bacteria. This souring can be used to great advantage, especially if you want to create dishes balanced with sweet and sour flavors. Sour amazake works fantastically in the creation of breads. It mimics some of the complexity of sourdough breads without the need to maintain a sourdough starter. At Larder most of the breads we produce incorporate amazake into their hydration. When we first developed these breads, we simply replaced a portion of the water called for with sour amazake that had its solids strained out. Sour amazake also serves as a fantastic seasoning for myriad applications—a favorite of ours is to bathe fresh, raw scallops or shrimp in it and serve them as a crudo. It also serves as a well-rounded base for vinaigrettes and even just as a flavorful brightening agent that you can add to a stock or sauce to give it a loving touch. Fruits compressed in a vacuum with either sweet or sour amazake are taken to another level, especially if they happen to be slightly lackluster on their own.

The longer your sour amazake ferments, the sourer it will become. There is also a strong possibility that it will become alcoholic instead of sour. Each of us produces these foods in different environments with drastically different microflora present. We encourage you to experiment with various parameters and variables to find a product that you enjoy. Toward that end, we recommend that once your sweet or sour amazake has a taste and flavor that you enjoy, you store it in airtight containers in the refrigerator. This will slow further fermentation. You can also pasteurize them to halt further development by heating them to 165°F (73°C)—but then you’ll lose the enzymatic action each one affords in addition to its inherent taste and flavor. Most of the further culinary preparations that you undertake will benefit greatly from the presence of the active enzymes, so store them cold instead of heat-treating.

How to Make Sweet Amazake

1. Combine 1 part cooked starch, 1 part koji, and 2 parts water.
2. Blend to increase the surface area of the starches.
3. Hold between 131°F (55°C) and 140°F (60°C) for 10 to 14 hours.
4. Store airtight under refrigeration.

How to Make Sour Amazake

1. Combine 1 part cooked starch, 1 part koji, and 4 parts water.
2. Hold between 131°F (55°C) and 140°F (60°C) for 10 to 14 hours.
3. Strain the amazake.
4. Hold at ambient room temperatures exposed to air, stirring at least once a day, and ferment for up to a week.
5. Store airtight under refrigeration.

The following excerpt is from Shih and Umansky’s new book Koji Alchemy: Rediscovering the Magic of Mold-Based Fermentation (Chelsea Green Publishing, May 2020) and is reprinted with permission from the publisher. 

Note: From a food safety standpoint working with koji to make amino pastes, amino sauces, shio koji or the amazake featured here is no different than making sauerkraut or kimchi. Keep your hands, utensils, ingredients, and work surfaces clean and, as with any fermented food, use the prescribed amount of salt if called for, which allows beneficial microbes to thrive and helps keep pathogens away.