Making Miso Paste at Home
This is a slow fermentation that transforms simple ingredients into a dense, umami-rich paste. By controlling the ratio of koji to beans, you decide the character of your miso, from sweet and light to dark and aggressive.
Cleanliness is the only non-negotiable rule.
Your greatest risk is unwanted mold growth. Sanitize every bowl, spoon, and the fermentation crock with high-proof alcohol or boiling water before they touch the ingredients.
- large stockpot
- heavy-duty potato masher or meat grinder
- stone crock or food-grade plastic bucket
- heavy weights (clean river stones or water jugs)
- cheesecloth and butcher paper
What goes in.
- 500gdried soybeans
- 500grice koji
- 200gsea salt
- 1 cupreserved bean cooking liquid
The Tight Pack
Oxygen is the enemy of a clean fermentation. When packing the mash, use your fist to press down with force, removing every air pocket to create a solid, uniform cake.
The method.
Soak the beans
Cover the soybeans in three times their volume of water and let them sit for 18 hours until they double in size.
Cook until soft
Drain the beans and simmer in fresh water for 3 to 4 hours. You should be able to crush a bean easily between your thumb and pinky finger.
Prepare the koji
In a large, sanitized bowl, crumble the koji rice by hand, then mix it thoroughly with the salt.
Mash the beans
Drain the beans, keeping one cup of the cooking water. Mash the beans into a uniform paste using a grinder or heavy masher. Add the reserved liquid if the paste is too stiff to handle.
Combine
Fold the bean paste into the salt-koji mixture. The resulting texture should be like wet sand or stiff dough.
Pack and weigh
Transfer to your crock in handfuls, pressing each layer down firmly. Cover the surface with plastic wrap pressed directly against the miso, then place your weights on top.
When it doesn't go to plan.
Use a light-colored rice koji for a milder, sweeter paste.
If white mold appears on the surface during fermentation, simply scrape it off; it is a harmless surface yeast.
The longer the miso ages, the deeper the color and the more complex the flavor becomes.
The ones that keep coming up.
How do I know if it has gone bad?
Miso is very forgiving due to the salt content. If the paste develops a foul, rotting smell or fuzzy, colored mold that penetrates deep into the paste, it should be discarded.
Can I use a glass jar?
You can, but avoid clear glass if possible as light can affect the fermentation. If you use clear glass, wrap the exterior in dark paper.
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