Natto (納豆) is one of Japan's most distinctive and nutritious traditional foods. Made by fermenting cooked soybeans with the beneficial bacterium Bacillus subtilis var. natto, it is famous for its sticky texture, stringy consistency, and strong, earthy aroma. Although its appearance and flavor may surprise first-time eaters, Natto is highly valued in Japan for its rich nutritional profile and has been enjoyed for over a thousand years.

A staple breakfast food throughout Japan, Natto is commonly served over steaming rice with soy sauce, mustard, and chopped green onions. It is also used in sushi rolls, noodles, rice bowls, salads, and even modern fusion dishes. Rich in protein, dietary fiber, probiotics, vitamin K₂, and other essential nutrients, Natto is considered one of Japan's most celebrated fermented foods.

What is Natto?

Natto is prepared by soaking and steaming soybeans before inoculating them with Bacillus subtilis var. natto. During fermentation, the bacteria produce enzymes and natural compounds that create Natto's characteristic sticky threads and savory umami flavor.

The fermentation process also enhances the nutritional value of soybeans, making Natto easier to digest while increasing beneficial compounds such as vitamin K₂ and the enzyme nattokinase.

Cuisine: Japanese

Category: Fermented Food

Origin: Japan

Preparation Time: 30 minutes (active)

Soaking Time: 12–18 hours

Cooking Time: 4–6 hours (or 45–60 minutes in a pressure cooker)

Fermentation Time: 20–24 hours

Aging Time: 1–2 days (recommended)

Total Time: Approximately 2–3 days

Servings: 8

Difficulty: Moderate

Ingredients

Main Ingredients

  • 500 g dried soybeans
  • 1 teaspoon Natto starter culture (Bacillus subtilis var. natto) or a small amount of fresh Natto as a starter
  • 1–2 tablespoons sterile warm water (to dissolve the starter if needed)

For Serving

  • Soy sauce
  • Japanese mustard (karashi)
  • Chopped green onions
  • Steamed Japanese rice

Optional Toppings

  • Raw egg yolk (where appropriate and safe to consume)
  • Nori strips
  • Sesame seeds
  • Kimchi
  • Grated daikon radish
  • Shiso leaves
  • Bonito flakes
  • Avocado
  • Chopped okra

Equipment Needed

  • Large bowl
  • Pressure cooker or heavy stockpot
  • Sterilized spoon
  • Fermentation containers or shallow trays
  • Clean cloth or perforated lid
  • Incubator, yogurt maker, or warm oven capable of maintaining 40°C (104°F)

Step 1: Soak the Soybeans

Rinse the dried soybeans thoroughly.

Place them in a large bowl and cover with plenty of water.

Soak for 12–18 hours at room temperature.

The beans will nearly double in size.

Step 2: Cook the Soybeans

Drain the soaked beans.

Cook until very soft:

Pressure Cooker

Cook for 45–60 minutes.

Stovetop

Simmer for 4–6 hours, adding water as needed.

The beans should mash easily between your fingers.

Drain well.

Step 3: Prepare the Starter

Sterilize all utensils and containers.

Dissolve the Natto starter culture in a small amount of sterile warm water, following the manufacturer's instructions if using a powdered culture.

If using fresh Natto as a starter, mix a small amount with warm sterile water until evenly dispersed.

Step 4: Inoculate the Soybeans

While the beans are still hot (around 80–90°C / 176–194°F), gently mix in the starter culture.

Ensure all beans are evenly coated without crushing them.

Transfer the beans into shallow sterilized containers in a layer approximately 3–5 cm (1–2 inches) deep.

Step 5: Ferment

Cover the containers with a clean cloth or perforated lid to allow airflow while protecting the beans.

Maintain a temperature of 40°C (104°F) for 20–24 hours.

During fermentation:

  • Fine white bacterial growth develops.
  • Sticky threads begin to form.
  • The aroma becomes stronger.
  • The beans develop their characteristic texture.

Step 6: Age the Natto

After fermentation, cool the Natto to room temperature.

Cover tightly and refrigerate for 24–48 hours.

This aging period allows the flavor to mellow and the texture to improve.

Step 7: Serve

Before eating, stir the Natto vigorously for 30–60 seconds.

This increases the sticky threads and creates a creamier texture.

Season with:

  • Soy sauce
  • Karashi (Japanese mustard)
  • Green onions

Serve over hot steamed rice.

Traditional Variations

Classic Breakfast Natto

Served with steamed rice, soy sauce, karashi, and chopped green onions.

Hikiwari Natto

Made from soybeans that are chopped before fermentation, resulting in a smoother texture and making it popular for sushi rolls and rice dishes.

Natto Maki

Natto wrapped in sushi rice and nori, offering a convenient and flavorful sushi variation.

Kimchi Natto

Combines spicy kimchi with Natto for a balance of tangy, spicy, and umami flavors.

Vegetarian Natto Bowl

Served with:

  • Avocado
  • Okra
  • Seaweed
  • Sesame seeds
  • Soft tofu
  • Brown rice

Chef's Tips

  • Use fresh, high-quality soybeans for the best texture.
  • Sterilize all equipment carefully to encourage proper fermentation.
  • Keep the fermentation temperature stable at around 40°C (104°F).
  • Avoid sealing the containers airtight during fermentation, as the bacteria require oxygen.
  • Stir thoroughly before eating to develop the characteristic sticky consistency.
  • Refrigerate for at least one day after fermentation to improve the flavor.

Common Mistakes

  • Using undercooked soybeans
  • Fermenting at the wrong temperature
  • Poor sanitation, leading to contamination
  • Sealing the container completely during fermentation
  • Skipping the refrigeration aging period
  • Using expired or inactive starter culture

Nutritional Information (Per Serving)

  • Calories: 200 kcal
  • Protein: 18 g
  • Carbohydrates: 14 g
  • Fat: 10 g
  • Fiber: 6 g
  • Sugar: 2 g
  • Sodium: 15 mg (before seasoning)

Values vary depending on serving size and toppings.

Serving Suggestions

Natto pairs wonderfully with:

  • Steamed Japanese rice
  • Miso soup
  • Tamagoyaki (Japanese rolled omelet)
  • Grilled salmon
  • Pickled vegetables (Tsukemono)
  • Nori sheets
  • Green tea
  • Brown rice
  • Udon or soba noodles

Storage

  • Refrigerate homemade Natto in an airtight container for up to 1 week.
  • Freeze for up to 2 months if needed; thaw overnight in the refrigerator before serving.
  • Stir before eating to restore its creamy, stringy texture.
  • Keep refrigerated at all times after fermentation.

Frequently Asked Questions

What gives Natto its sticky texture?

The fermentation bacteria produce natural polymers that create the characteristic sticky threads and creamy consistency when the beans are stirred.

Why does Natto have such a strong smell?

The fermentation process produces aromatic compounds that give Natto its distinctive earthy aroma, which becomes milder after refrigeration and when mixed with seasonings.

Is Natto healthy?

Yes. Natto is rich in protein, dietary fiber, probiotics, vitamin K₂, iron, and other nutrients. It also contains nattokinase, an enzyme formed during fermentation.

Can I make Natto without a starter?

A starter culture is strongly recommended for consistent and safe fermentation. A small amount of fresh Natto can also be used to inoculate a new batch.

Why should Natto be stirred before eating?

Stirring incorporates air and enhances the sticky threads, creating a smoother texture and helping distribute the flavors of the seasonings evenly.

Final Thoughts

Natto is one of Japan's most unique and nutritious traditional foods, combining centuries-old fermentation techniques with exceptional health benefits and rich umami flavor. Although its sticky texture and distinctive aroma may take some getting used to, it has earned a treasured place in Japanese cuisine as a wholesome everyday staple. Whether served simply over steaming rice, rolled into sushi, or incorporated into modern dishes, Natto offers an authentic taste of Japan's fermentation heritage and demonstrates how simple ingredients can be transformed into something truly remarkable.