Hakko Anko (Fermented Sweet Red Beans)

Fermented sweet red bean paste, known as hakko anko, is a gentle twist on a classic Japanese staple. Instead of sugar, this version uses rice koji to bring out the natural sweetness of azuki beans through fermentation. After completing fermented food school in Kyoto, I wanted to start sharing more fermented recipes that are practical for home cooks. This recipe is the first in that series and a great place to begin if you are curious about fermentation. It is simple and and a commonly used in Japanese cooking.

What Is Sweet Red Bean Paste (Anko)?

Sweet red bean paste, known as anko, is a Japanese food typically used to make desserts like mochi, dorayaki, and anmitsu. It is made by cooking azuki beans until tender, then sweetening and mashing them into a smooth or chunky paste. The two most common styles are koshian, which is silky and smooth, and tsubuan, which keeps the bean skins for more texture. I have both a traditional koshian recipe and a traditional tsubuan recipe you can follow at home. This recipe, however, is fermented so it uses no sugar unlike the traditional versions.

What Is Fermented Sweet Red Bean Paste?

Fermented sweet red bean paste is a modern variation of anko that relies on fermentation instead of added sugar for sweetness. Cooked azuki beans are mixed with rice koji, which contains natural enzymes that break down starches into natural sugars over time. As the mixture ferments, the flavor becomes gently sweet and more complex without tasting heavy. This method creates a softer, rounder taste while keeping the ingredients simple. It’s a good way to enjoy anko if you prefer a lighter natural sweetness.

Ingredients for Fermented Sweet Red Bean Paste

This fermented sweet red bean paste uses just a few simple ingredients. 

• Dried adzuki beans
  The base of the recipe. Choose good quality beans for the best flavor and smooth texture.
• Rice koji
  Provides the natural enzymes needed for fermentation and sweetness. Fresh or dried rice koji both work.
• Water
  Used for cooking the azuki beans and adjusting the consistency of the paste.
• Salt (optional)
  A small pinch helps balance the sweetness and brings out the flavor of the beans.

How to Make Fermented Sweet Red Bean Paste

1. Cook the azuki beans in a pressure cooker

2. Cool and mix the ingredients

3. Finish and store

Taste the paste once fermentation is complete. If desired, add a small pinch of salt to balance the sweetness and also blend it with an immersion blender if you prefer a smooth texture. Let it cool completely, then store in the refrigerator for a few days or freeze for longer storage.

How to Use Fermented Sweet Red Bean Paste

Fermented sweet red bean paste can be used in the same way as ordinary red bean paste. It works well as a filling for mochi, dorayaki, and other Japanese sweets. You can also spread it on toast, stir it into yogurt, or serve it with fruit for a simple snack. Because the sweetness is gentle, it pairs easily with both traditional desserts and everyday foods. This makes it a flexible option wherever you would normally use anko.

How to Store Fermented Anko

Once fermentation is complete, let the anko cool completely before storing. Keep it in an airtight container in the refrigerator for up to one week. For longer storage, divide it into small portions and freeze. Frozen fermented anko keeps well for about one month and can be thawed in the refrigerator as needed. Stir after thawing to restore a smooth texture.

Variations Using Other Beans

This fermented anko method works well with more than just azuki beans. By changing the beans, you can create new flavors while keeping the same gentle sweetness from rice koji.

Chickpea version
Chickpeas create a smooth and mild paste that works well for spreads and toast. Cook them until very soft, then ferment with rice koji in the same way as azuki beans. The flavor is light and slightly nutty, which pairs nicely with fruit or yogurt.

Mung bean version
Mung beans create a very smooth and light paste with a clean sweetness. They are often used in Asian desserts, so they pair naturally with fermentation. Cook them until fully soft, then remove any loose skins for a silkier texture before mixing with rice koji. This version is especially good for filling mochi or serving with fruit. Mung beans ferment quickly, so start checking the flavor a little earlier than with azuki beans.

White bean version
White beans, such as navy or cannellini beans, create a smooth and neutral base that lets the fermented sweetness shine. Their mild flavor makes them easy to use in both Japanese and everyday desserts. Cook the beans until very soft, then blend or mash well before adding the rice koji. This version is ideal if you want a light colored, gently sweet paste that works well in mochi or as a spread.

Each of these beans follows the same fermentation process. Cook until very soft, cool to below 60°C, then mix with rice koji and ferment until lightly sweet. Try one at a time to see which flavor you enjoy most.