Large-Batch Homemade Miso Paste Recipe

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Serves kg

Vegan

Ready to take your homemade miso to the next level? This guide walks you through making a large batch of miso, including the tools and techniques you’ll need!

First time making miso? Start with my small-batch miso paste recipe!

Why You Will Love This Recipe

Makes about 4 kg of miso, perfect if you use it regularly.
You’ll learn the tools and techniques needed for making a larger batch.
The step-by-step video and tips help you feel confident throughout the process.

Learn more here: What Is Miso? A Simple Beginner’s Guide

Recipe Ingredients

You’ll need the following ingredients to make this Miso Paste Recipe:

Soybeans: Use dried soybeans, preferably larger ones if available. I use Toyomasari, a Japanese variety with a naturally rich flavor, but any good-quality dried soybeans will work.
Dried Rice Koji: Rice koji is an essential ingredient in miso. Its enzymes break down proteins and starches, helping develop the miso’s rich umami and subtle sweetness. It can be difficult to find outside Japan, but it is often available at Japanese grocery stores or online.
Salt: Any regular cooking salt you normally use will work. Choose a fine-grain salt, as very coarse salt may not dissolve or mix evenly throughout the miso.

Equipment

Here are the essential tools you’ll need to make a large batch of miso:

Pressure Cooker or Large Pot: A pressure cooker saves a lot of time when cooking soybeans. Depending on its size, you may need to cook them in a few batches. If you don’t have one, simply simmer the soybeans in a large pot, adding water as needed, until they are soft enough to crush easily between your fingers.
Something to Mash the Soybeans: I place the cooked soybeans in a large plastic bag and crush them with a rolling pin. Since the soybeans will still be hot, be sure to wear gloves or oven mitts. A potato masher or food processor also works well.
Large Mixing Bowl: Use a bowl or container large enough to mix the mashed soybeans, koji, and salt. If you don’t have one, a large, sturdy, food-grade plastic bag makes a good substitute.
Fermentation Container: Use a clean, food-grade plastic container or glass jar. For this recipe, I use a 5-liter plastic container.
Inner Lid: Place an inner lid on top of the covered miso before adding the weight. This helps spread the pressure evenly and keeps the surface flat. If you don’t have one, use a flat plate instead.
Weight: Placing a weight on top limits the miso’s exposure to air, helping reduce the risk of mold and oxidation. For this 4 kg batch, use a weight of about 2–3 kg. A water-filled bottle or an unopened bag of salt works well as a substitute.
Plastic Wrap: Press plastic wrap directly onto the surface of the miso to help keep air out during fermentation.

How To Make Miso Paste: STEP BY STEP

Here’s a quick visual guide! Check the recipe card below for the video and full details!

Soak the Soybeans

Place the soybeans in a large bowl. Cover with plenty of water and soak for 6-8 hours.

After soaking, the soybeans will become about 2.5 times larger.

Make the Miso

Step 1

Cook the soybeans in a pressure cooker.

Step 2

Reserve some of the cooking liquid for later.

Step 3

Mash the soybeans in a plastic bag using a rolling pin.

Step 4

Combine the rice koji and sea salt.

Step 5

Add the mashed soybeans and mix well.

Step 6

If the mixture feels too dry, add a little of the reserved cooking liquid at a time.

Step 7

Form the mixture into balls and pack them firmly into the container, pressing down with your fist.

Step 8

Flatten the surface and sprinkle salt around the edges, where mold is most likely to form.

Step 9

Cover the surface tightly with plastic wrap. Place an inner lid and a weight on top.

Step 10

Cover the container with a plastic bag, then store it in a cool, dark place out of direct sunlight for 6–12 months.

Recipe Tips

Mash in batches: There will be a large amount of soybeans, so don’t try to mash them all at once. Work in a few smaller batches to make the process easier and more even.
Adjust the moisture: If the mixture feels too dry or crumbly, add a little of the reserved soybean cooking liquid at a time until it comes together.
Remove air pockets: Air pockets can encourage unwanted mold during fermentation. Shape the mixture into miso balls, then pack them tightly into the container, pressing down well as you go.
Cover the surface tightly: Press plastic wrap directly onto the surface of the miso to limit its exposure to air.

Where To Ferment Miso Paste

Miso fermentation takes place at room temperature, not in the refrigerator. Find a cool, dark place out of direct sunlight for your container. Suitable spots include a storeroom, basement, pantry, entrance area, or under-floor storage. In my case, I like to keep mine in a pantry under the stairs.

One-Month Fermentation Check

Once the miso has been fermenting for about one month, check its progress.

You may notice some liquid rising to the surface. This is called miso tamari, a rich liquid that naturally separates from the miso as it ages. A little miso tamari has started to appear, and the miso looks moist with no mold, which is a good sign.

Mix the miso from top to bottom, including the miso tamari. Then flatten the surface again, cover, and return the container to its fermentation spot.

Six-Month Fermentation Check

After about six months, check the miso again. By this time, the color should be deeper, and the aroma should be richer than before.

You may notice more miso tamari on the surface. This is normal and can be mixed back into the miso.

Take a small amount from about 1 cm below the surface and taste it. If it has a balanced salty, savory flavor, your miso is ready to use. If you prefer a deeper and richer flavor, cover it again and let it age longer.

Tips for the Aging Period

Homemade miso usually takes 6 to 12 months to be ready, depending on your taste preference and environment.
A longer aging period produces a richer taste, while a shorter period gives a lighter flavor.
Miso is often prepared in winter because the cold temperatures reduce bacteria and mold, allowing fermentation to progress slowly and steadily. It starts fermenting slowly in spring, accelerates in summer, and then slows down again in autumn, deepening the flavors.
If miso over-ferments, the aroma can become too strong, occasionally developing a sour taste or an ammonia-like odor.

Signs of Properly Aged Miso: What To Look For

Here are things to look for to know if your miso is aged and ready to eat:

Color: Soybeans start off light brown, but as they age in fermentation, they gradually darken. When they reach a miso-like color, it’s a sign that it’s aging correctly.
Aroma: At the beginning of preparation, there isn’t much smell. However, as it ages, it develops a distinct miso-like aroma; then you’ll know it has been properly aged.
Taste: As miso ages, its taste becomes more profound and complex. Be sure to taste it. Take a piece of miso from about 1cm below the surface, mix it with hot water, and taste. Based on the taste, decide whether to extend or stop the fermentation.

Dealing with Mold During Fermentation

If mold appears, remove the surrounding area with a spoon. If you see a fluffy white ring on the edge of the container, it is also mold. Be sure to remove all of it, and wrap the miso tightly to prevent air contact during fermentation.

Storage

Once the miso reaches your preferred flavor, transfer it to the refrigerator to slow down further fermentation. I recommend keeping the portion you plan to use soon in an airtight container and storing the rest in freezer bags in the refrigerator.

You can also store miso in the freezer. It doesn’t freeze solid; it may become slightly stiff, but you can still easily scoop it out and use it.

How To Use Miso Paste

Homemade miso paste can be used in many different dishes, not just miso soup. Check out my collection of recipes using miso paste.

Your Questions Answered

How long does homemade miso take to ferment?

Homemade miso usually takes about 6 months to 1 year to ferment. The longer it ages, the deeper and richer the flavor becomes.

Where should I keep the container while the miso ferments?

Keep the miso container in a cool, dark place at room temperature, away from direct sunlight and heat. A pantry, cupboard, or storage area works well.

What should I do if mold appears?

If you see a small amount of mold on the surface, don’t panic. Carefully remove the mold and a little of the miso around it with a clean spoon. Then wipe the container, cover the surface tightly again, and continue fermenting.

How do I know when miso is ready?

Miso is ready when it has a rich aroma, deep color, and a balanced, salty, savory flavor. To taste it, take a small amount from about 1 cm below the surface, mix it with hot water, and check the flavor.

I found liquid on top of the miso. What should I do?

The liquid on top is called tamari, and it’s a natural part of the aging process. It has a rich, concentrated miso flavor, so don’t discard it. Simply mix it back into the miso before using.

Does homemade miso need to be refrigerated after fermentation?

Yes, once the miso has fermented to your liking, store it in the refrigerator. This slows down the fermentation and helps keep the flavor stable for longer.

If you have more questions, feel free to leave a comment below!

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