How to Make Miso
Craft your own miso paste from soybeans, koji, and salt. A deeply savory fermented staple used in soups, marinades, and dressings.
Miso is a deeply savory Japanese fermented paste made from soybeans, koji (rice or barley inoculated with Aspergillus oryzae mold), and salt. The koji enzymes slowly break down the soybeans' proteins and starches over weeks to months, creating a complex, umami-rich paste used in soups, marinades, dressings, and glazes. White miso (shiro) is mild and sweet after just 1–3 months; red miso (aka) develops bold depth over 6–18 months or longer. Homemade miso is deeply satisfying — once packed, it requires little attention beyond monthly checks, rewarding your patience with extraordinary flavor.
Equipment
- Large pot (4+ quart)
- Large mixing bowl
- Kitchen scale (essential — ratio precision matters)
- Potato masher or food processor
- Fermentation crock, large glass jar, or food-grade container
- Plastic wrap or wax paper
- Weight (plate + heavy jar, or zip-lock bag filled with salt water)
- Clean cloth or towel
Ingredients
- Dried soybeans (1 cup / 200g)
- Rice koji (2 cups / 400g) — the enzyme-producing culture
- Sea salt or kosher salt (70g total — about ¼ cup + 1 tbsp)
- Soybean cooking liquid, reserved (up to 1 cup)
Workflow
Soak Soybeans
12–18 hoursRinse and soak
Rinse 1 cup of dried soybeans thoroughly. Place in a large bowl and cover with water by at least 3 inches — the beans will roughly triple in size.
Soak overnight
Let soak at room temperature for 12–18 hours. In hot weather (above 85°F / 29°C), soak in the refrigerator to prevent fermentation from starting prematurely.
Ready When
Cook Soybeans
3–4 hours (45–60 minutes in a pressure cooker)Drain and add fresh water
Drain soaked beans, place in your large pot, and cover with fresh water by 2 inches.
Bring to boil, then simmer
Bring to a boil, skim off the foam that rises, then reduce to a gentle simmer. Cook for 3–4 hours until beans are very soft.
Reserve cooking liquid
Before draining, scoop out and reserve 1 cup of the soybean cooking liquid. You may need it to adjust moisture when mixing.
Drain and cool
Drain beans and spread them out to cool. They must cool below 140°F (60°C) — ideally to room temperature — before mixing with koji.
Beans must cool below 140°F (60°C). Heat above this temperature kills koji enzymes and ruins the fermentation.
Ready When
Mix Koji, Salt & Beans
20–30 minutesMix koji and salt
In a large bowl, combine 2 cups of rice koji with the salt (reserving 1 tablespoon for the top later). Mix thoroughly with your hands, breaking up any clumps.
Mash the soybeans
Mash cooled soybeans with a potato masher until mostly smooth with some texture remaining. A food processor works too — pulse rather than puree to keep some texture.
Combine beans with koji mixture
Add mashed soybeans to the koji-salt mixture. Knead together thoroughly until uniform. If the mixture is too dry to hold together, add reserved cooking liquid a tablespoon at a time. The finished mixture should hold together like thick cookie dough.
Form into balls
Form the miso mixture into baseball-sized balls, squeezing firmly to compact them and remove air pockets.
Ready When
Pack & Begin Fermentation
15 minutesPack into container
Throw each miso ball forcefully into the clean, dry crock or jar — the impact helps eliminate air pockets. Press down firmly after each addition. Smooth the top surface flat.
Salt the surface
Sprinkle the reserved tablespoon of salt evenly over the entire top surface. This salt cap prevents mold from colonizing the exposed surface.
Cover and weight
Press plastic wrap directly onto the entire miso surface with no air gaps. Place a plate or lid on top, then add your weight (a jar of water, or a zip-lock bag filled with brine). The weight should equal roughly 20–30% of the miso weight.
Store in a cool, dark place
Cover the crock with a clean cloth and store at 60–75°F (15–24°C). A basement, pantry, or cool closet is ideal.
Ready When
Fermentation & Monthly Checks
1–3 months (white miso) to 6–18 months (red miso)Check monthly
Once a month, remove the weight and plastic wrap. Inspect the surface — scrape off any mold (white, blue, or green) with a clean spoon, taking a thin layer of miso with it. The miso below is fine. Press fresh plastic wrap back onto the surface and replace the weight.
Taste periodically
Starting at 4–6 weeks for white miso, taste a small sample from the center using a clean spoon. It should be salty, savory, and slightly sweet. The flavor deepens noticeably over time.
Ready When
Storage
Transfer and refrigerate
Once the miso reaches your desired depth of flavor, transfer to clean glass jars and refrigerate. Cold storage slows fermentation to nearly nothing while allowing flavor to continue developing gently.
Troubleshooting
Common issues and how to fix them. Something look off? Find your symptom below.
Food Safety
Hygiene
Apply a generous salt cap directly on the miso surface before sealing. This protective layer prevents mold from penetrating into the miso body. Do not skip this step.
Press plastic wrap or wax paper directly onto the entire miso surface after salting, eliminating all air pockets. Air exposure is the primary cause of surface mold.
Standard miso contains soy (a common allergen) and may contain gluten if made with barley or wheat koji. Check koji source if serving those with gluten sensitivity.
Equipment
Use only food-grade Aspergillus oryzae koji from reputable suppliers. Never use wild mold or improvise. Other Aspergillus species can produce aflatoxins, which are carcinogenic.
Apply significant weight (equal to 20–30% of the miso weight) on top of the pressed surface. This forces out air pockets and helps the miso form its protective acidic environment.
Temperature
Ferment in a cool, dark place at 59–72°F (15–22°C). Avoid temperature fluctuations. A basement, cool pantry, or closet is ideal.
Storage
Check miso every 2–4 weeks. Scrape off any surface mold, redistribute the weight, and re-seal. Regular inspection is the key to a successful long ferment.
Miso is very high in sodium — a tablespoon contains 600–1000mg. Use sparingly if managing sodium intake. Never add miso to boiling liquid; add it off the heat to preserve probiotics and enzymes.
When to Discard
Mold penetrating below the surface salt cap
Surface mold on the protective salt cap is common and can be scraped away safely — the miso beneath is typically fine. However, if mold has grown into the miso body itself (below 1 inch from the surface), assess the rest carefully. Miso that smells and tastes correct below the mold line is usually still safe.
Strong, persistent ammonia or rotten smell
Miso should smell earthy, savory, and intensely umami. A faint ammonia whiff that quickly dissipates can be normal in very aged miso. A strong, persistent ammonia smell or a clearly rotten, putrid odor indicates bacterial contamination — discard the affected area or the whole batch.
Storage Guidelines
Room Temperature
Ferment in a cool, dark location: 1–3 months for white/shiro miso, 6–18 months for standard miso, 2–3 years for dark red/hatcho style.
Refrigerated
Finished miso keeps refrigerated for 1–2 years. Flavor continues to slowly and gently develop even in the cold.
Frozen
Miso can be frozen to halt fermentation completely. Thaw in the refrigerator before use. Freezing does not damage miso but stops all further flavor development.
Shelf Life
Refrigerated: 1–2 years. High-salt miso (10%+ salt) may last even longer. Quality slowly declines after 2 years but miso remains safe.
Flavor Variations
Once you have mastered the basics, try these flavor combinations to take your ferments to the next level.
Shiro (White/Mellow) Miso
Sweet, mild, and creamy — fermented for just 2–8 weeks with a high ratio of rice koji to soybeans. The most versatile style: excellent in dressings, light soups, marinades, butter, and even desserts.
Ingredients
- 500g soybeans, soaked and cooked until very soft
- 500g rice koji (equal weight to beans)
- 130g sea salt (approximately 11% of total weight)
Short fermentation at room temperature (70–75°F) for 3–8 weeks.
The high koji ratio produces significant sweetness — this is the style to use in sweet glazes and dessert applications.
Mugi (Barley) Miso
Fermented with barley koji instead of rice koji, mugi miso has a distinctive earthy, robust, slightly grainy flavor — the traditional farmhouse style of Kyushu, Japan.
Ingredients
- 500g soybeans, soaked and cooked
- 500g barley koji
- 130g sea salt
Barley koji produces a slightly denser, earthier flavor than rice koji.
Ferment for 3–12 months for medium to full flavor development.
Chickpea Miso
A lighter, slightly nutty and sweet miso made from chickpeas instead of soybeans — less intense, faster-fermenting, and excellent for those avoiding soy. A wonderful introduction to miso-making.
Ingredients
- 500g dried chickpeas, soaked and cooked until very soft
- 400g rice koji
- 115g sea salt
Chickpea miso ferments faster than soybean miso — start tasting at 6 weeks.
The finished color tends toward a warm caramel-tan rather than the deeper brown of soybean miso.
Yuzu Citrus Miso
Finished white miso blended with yuzu zest and juice — bright, floral, and citrusy. A finishing technique that transforms mild shiro miso into a special condiment for fish, vegetables, and grilled tofu.
Ingredients
- 250g finished white miso
- Zest of 2 yuzu (or Meyer lemon as a substitute)
- 1 tbsp yuzu juice
- 1 tsp mirin
This is a finishing blend — only add yuzu to fully fermented and cooled miso.
Store in the refrigerator and use within 3 months for best flavor.
Walnut & Sesame Dengaku Miso
A classic dengaku-style miso glaze for grilling — toasted walnuts and sesame seeds blended into sweet white miso create an extraordinary savory-sweet glaze for eggplant, tofu, and root vegetables.
Ingredients
- 200g shiro (white) miso
- 50g toasted walnuts, finely chopped
- 2 tbsp toasted sesame seeds
- 2 tbsp mirin
- 1 tbsp sake
- 1 tbsp sugar
Combine all ingredients and cook over low heat, stirring constantly, for 3–5 minutes until slightly thickened.
Exceptional spread on grilled eggplant, roasted root vegetables, or fried tofu.
Black Bean Miso
Rich, deeply colored miso made from black beans — the anthocyanins produce an almost purple-brown paste with a slightly sweeter, earthier flavor than standard soybean miso.
Ingredients
- 500g dried black beans, soaked and cooked
- 400g rice koji
- 120g sea salt
Black bean miso can ferment to good depth in 3–6 months.
Excellent in dark stews, black bean soups, and BBQ-style glazes.
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