Sugar-Free! Complete Guide to Making Fermented Anko (Sweet Bean Paste) | Benefits, Recipe, and Tips for Success

Fermented anko is a sweet bean paste made only with adzuki beans and rice koji, without any added sugar. The enzymes in the rice koji saccharify the starch in the adzuki beans, creating a gentle sweetness, much like refined wagashi (Japanese confectionery).

In recent years, with the growing health consciousness, searches for "fermented anko" have surged, mainly on social media and recipe websites.

It's attracting attention as a new staple for baking, breakfast, and desserts due to its appealing qualities: it's sweet without sugar, and it's good for gut health.

This page compiles everything you need to know about fermented anko, from its benefits to recipes using rice cookers, yogurt makers, and pressure cookers, as well as recommended ways to eat it, as a保存版 (permanent reference).

We'll also provide a detailed explanation from the perspective of a brewery, focusing on choosing the right rice koji, which is key to "making fermented anko without failure."

Benefits of Fermented Anko: The Secret to its Sugar-Free Sweetness and Health Advantages

In short, the benefit of fermented anko is that it combines the best qualities of two ingredients: "adzuki beans" and "rice koji."

Benefits of Adzuki Beans

Adzuki beans are rich in polyphenols, dietary fiber, saponin, iron, and potassium.

In Japan, adzuki beans have long been eaten on special occasions as an ingredient that "wards off evil spirits."

It's also a welcome ingredient for those concerned about swelling or interested in antioxidant effects.

Benefits of Rice Koji

Rice koji is a fundamental ingredient in Japanese fermented foods, made by cultivating koji mold (Aspergillus oryzae) on steamed rice.

The enzymes produced by koji mold (such as amylase and protease) break down starch into glucose and protein into amino acids. This is believed to aid digestion and improve the intestinal environment.

Summary of Fermented Anko Benefits

• Sugar-free, making it less likely to cause a sudden spike in blood sugar.
• Rich in dietary fiber, supporting a healthy gut environment.
• Oligosaccharides from rice koji feed beneficial gut bacteria.
• Also provides B vitamins and minerals.

However, fermented anko is not "calorie-free." It has a natural sweetness from glucose, so be mindful of overconsumption.

How to Make Fermented Anko: Basic Steps

The process of making fermented anko can be simply divided into the following three steps:

1. Boil adzuki beans until soft.
2. Mix rice koji into the adzuki beans after cooling them to around 60°C.
3. Ferment for 8 to 10 hours at approximately 55-60°C.

The most crucial aspects here are "temperature management" and "the quality of the rice koji."

Koji mold enzymes are most active at 55-60°C and become inactive above 70°C. Conversely, if the temperature is too low, bacteria can multiply, leading to a sour taste.

Therefore, when making fermented anko at home, it is recommended to use equipment that can maintain a stable temperature.

From here, we will introduce recipes for fermented anko using a rice cooker, yogurt maker, and pressure cooker, respectively.

How to Make Fermented Anko in a Rice Cooker

The easiest and most popular method for making fermented anko is using a rice cooker. By utilizing its keep-warm function, you can achieve authentic results without special equipment.

Ingredients (for a manageable batch)

• Adzuki beans …… 200g
• Rice koji (fresh or dried) …… 200g
• Water …… appropriate amount
• Salt …… a pinch

Steps to Make Fermented Anko in a Rice Cooker

1. Quickly rinse the adzuki beans and perform "shibukiri" (boiling off bitterness) 1-2 times in plenty of water.
2. Add fresh water and simmer on low heat for about an hour until the adzuki beans can be easily crushed between your fingers.
3. Cool the beans to around 60°C (a temperature you can touch with your hand) while leaving a little liquid.
4. Thoroughly mix in the loosened rice koji.
5. Transfer to the inner pot of the rice cooker, cover with a damp cloth with the lid open, and set to keep-warm mode for 8-10 hours.
6. Stir every 2-3 hours for a more even result.

The key point is to ferment "with the lid open."

The keep-warm temperature of a rice cooker is quite high, around 70°C, so closing the lid would inactivate the koji mold enzymes.

How to Make Fermented Anko with a Yogurt Maker

If you have a yogurt maker with temperature control, you can make fermented anko most consistently. Recently, many models can be set up to 60°C, making them a popular item for fermentation enthusiasts.

Steps to Make Fermented Anko with a Yogurt Maker

1. Similar to the rice cooker recipe, boil the adzuki beans until soft.
2. Cool to around 60°C and mix with rice koji.
3. Place in a container for the yogurt maker and set to 60°C for 8 hours.
4. Stir 1-2 times during the process for a more uniform result.

The advantage of a yogurt maker is, without a doubt, its "minimal temperature fluctuation." For beginners who are unsure about temperature control, this is the most recommended method.

How to Make Fermented Anko with a Pressure Cooker

For those who "want to save time as much as possible," using a pressure cooker is recommended.

It significantly shortens the time needed to cook the adzuki beans.

Steps to Make Fermented Anko with a Pressure Cooker

1. Place adzuki beans and water in a pressure cooker and heat for about 10-15 minutes after pressurizing (adjust depending on the model).
2. Release pressure naturally, open the lid, and cool to around 60°C.
3. Add rice koji and mix thoroughly.
4. Transfer to a rice cooker or yogurt maker for fermentation and keep warm for 8-10 hours.

Since it's difficult to maintain a temperature of 55-60°C solely with a pressure cooker, a hybrid method of "boiling in a pressure cooker + fermenting in a rice cooker/yogurt maker" is more practical.

This method combines the benefits of quick pre-boiling and a stable fermentation environment.

Reasons for Fermented Anko Failure and the Importance of Choosing Rice Koji

"I tried making fermented anko, but it wasn't sweet," or "It turned sour."

These are common comments. The quality of the finished fermented anko is largely determined by "the quality of the rice koji."

Main Causes of Failure

• The temperature was too high, inactivating the koji mold enzymes.
• The temperature was too low, allowing bacteria to grow.
• The enzyme activity (saccharifying power) of the rice koji was weak.
• The adzuki beans were too hard for the enzymes to penetrate.

Among these, the "power of the rice koji itself" is often overlooked.

Some dried koji sold in supermarkets may have lost enzyme activity during long periods of distribution.

Even with the same recipe and temperature, if the rice koji is different, the sweetness of the finished product will be completely different.

The Strength of Rice Koji Prepared at the Sake Brewery

At our brewery, we leverage the koji-making techniques honed through daily sake brewing to prepare our own rice koji.

For brewing, the "saccharifying power" – the ability to efficiently convert rice starch into sugar – is paramount.

When used for fermented anko, this saccharifying power directly translates into a "natural sweetness" in the finished product.

• Careful management of temperature and humidity during the koji production process.
• Potent koji where koji mold has thoroughly penetrated each grain of steamed rice.
• A simple production process using only rice and koji mold, without unnecessary additives.

If you've tried making fermented anko but felt the sweetness was somehow lacking, we particularly encourage you to try our brewery-made rice koji.

You'll be surprised by its rich sweetness, making it hard to believe no sugar was added.

▶︎ Our rice koji: [Insert product page URL]

How to Eat Fermented Anko: From Classic to Creative

Once you've made your fermented anko, you'll want to enjoy it in various ways, right?

Here are some recommended ways to eat fermented anko.

Classic Ways to Enjoy Fermented Anko

• Oshiruko/Zenzai: Just dilute with hot water or soy milk for a warming bowl.
• An-butter toast: Spread on toast with butter for breakfast.
• Daifuku/Dorayaki: Use as a filling for homemade Japanese sweets.
• Shiratamanko: Combine with chewy shiratama for a simple snack.

Healthy Arrangement Recipes

• Fermented anko yogurt: Add 1-2 tablespoons to plain yogurt.
• Fermented anko soy latte: Dissolve a spoonful in warm soy milk.
• Fermented anko granola: Top granola with a small amount for breakfast.
• Fermented anko ice cream: Serve over vanilla ice cream for a simple dessert.

Since it's sugar-free, it's great as a snack for children or as a "less guilty sweet" for those mindful of their sugar intake. Its applications are wide-ranging in cooking too, such as adding richness to teriyaki dishes or as a secret ingredient in dressings.

How to Store Fermented Anko

Fermented anko can be stored in a clean container in the refrigerator for about a week, or in the freezer for about a month.

Wrapping it in small portions and freezing is convenient for future use. When thawing in a microwave, it's best to warm it briefly and gradually to prevent the enzymes from becoming completely inactive.

Summary: "Rice Koji" Determines the Taste of Fermented Anko

You can easily enjoy making fermented anko at home using common tools like rice cookers, yogurt makers, and pressure cookers.

While the recipe itself is simple, the biggest factor determining its outcome is "choosing the right rice koji."

Rice koji, refined through the brewing process, truly shows its value in making fermented anko. By using rice koji with strong saccharifying power, the fermented anko that you might have felt was "somehow lacking" will transform into an astonishingly natural and deep sweetness.

Please try upgrading your homemade fermented anko with our carefully crafted brewery-made rice koji.