Natto, a traditional Japanese food made from fermented soybeans, is renowned for its unique texture and flavor. This nutritious delicacy has been enjoyed in Japan for centuries and is gaining popularity worldwide due to its health benefits. To ferment natto at home, soak dried soybeans overnight, cook them until tender, then inoculate with Bacillus subtilis bacteria and ferment at a consistent warm temperature for 24-48 hours.

The process of fermenting natto requires attention to detail and proper sanitation. Soaking the soybeans ensures even hydration, leading to more consistent cooking and fermentation. After cooking, the beans are mixed with a natto starter culture, which contains the necessary bacteria to initiate fermentation. Maintaining the right temperature during fermentation is crucial for developing natto’s characteristic sticky texture and umami flavor.

While the fermentation process may seem daunting, making natto at home allows for customization and ensures a fresh, probiotic-rich product. Home-fermented natto can be tailored to personal taste preferences by adjusting fermentation time and temperature. With just a few simple ingredients and proper technique, anyone can create this staple of Japanese cuisine in their own kitchen.

Understanding Natto and Its Origins

Natto is a traditional Japanese food with a rich history and unique nutritional profile. This fermented soybean dish has been a staple in Japanese cuisine for centuries, offering both cultural significance and health benefits.

Defining Natto

Natto is a fermented soybean product characterized by its sticky texture, strong flavor, and pungent aroma. It is made by fermenting cooked soybeans with Bacillus subtilis bacteria. The fermentation process creates a slimy, stringy coating around the beans.

Natto is typically served over rice and seasoned with soy sauce, mustard, or green onions. Its distinctive taste and texture can be polarizing, with some people loving it and others finding it challenging to enjoy.

Historical Significance in Japanese Culture

Natto has deep roots in Japanese culinary tradition. Historical records indicate its presence in Japan as early as the 11th century, though some theories suggest it may have existed even earlier.

One popular legend attributes natto’s discovery to a samurai who stored boiled soybeans in straw bags. The natural bacteria in the straw allegedly caused fermentation, leading to the creation of natto.

Natto has long been valued in Japanese culture for its perceived health benefits and as a practical, preserved food source. It remains an important part of Japanese cuisine, particularly as a breakfast food.

Nutritional Profile of Natto

Natto boasts an impressive nutritional profile, making it a powerhouse of health benefits:

• High in protein: Natto is an excellent plant-based protein source.
• Rich in vitamin K2: It contains one of the highest concentrations of this nutrient found in food.
• Probiotic properties: The fermentation process creates beneficial bacteria.
• Fiber content: Natto provides a good amount of dietary fiber.
• Mineral-rich: It contains iron, calcium, and magnesium.

The fermentation process also enhances the bioavailability of nutrients in the soybeans. This makes natto not only nutritious but also easier for the body to absorb its beneficial components.

Health Benefits of Natto

Natto offers numerous health advantages due to its unique nutritional profile and bioactive compounds. This fermented soybean product contains essential nutrients and beneficial bacteria that support various bodily functions.

Nattokinase and Heart Health

Nattokinase, an enzyme found in natto, plays a crucial role in cardiovascular health. This enzyme helps dissolve blood clots and may reduce the risk of heart disease. Nattokinase has shown potential in lowering blood pressure and improving circulation.

Research suggests that regular consumption of natto may contribute to a decreased risk of cardiovascular events. The enzyme’s ability to break down fibrin, a protein involved in blood clot formation, makes it valuable for maintaining healthy blood flow.

Natto’s high vitamin K2 content also supports heart health by helping to prevent calcium buildup in arteries. This nutrient directs calcium to bones and teeth, where it’s needed most.

Digestive Health Advantages

Natto’s fermentation process creates beneficial probiotics that support digestive health. These live bacteria help maintain a balanced gut microbiome, which is essential for proper digestion and nutrient absorption.

The probiotics in natto may:

• Improve bowel regularity
• Reduce inflammation in the digestive tract
• Enhance the immune system
• Aid in the breakdown of food particles

Consuming natto regularly can contribute to a healthier gut environment, potentially alleviating digestive issues and promoting overall well-being.

Protein and Vitamin Content

Natto is a nutrient-dense food, rich in high-quality plant-based protein. It provides all essential amino acids, making it a complete protein source for vegetarians and vegans.

Key nutrients found in natto include:

• Vitamin K2 (menaquinone)
• Vitamin C
• Iron
• Manganese
• Copper

Vitamin K2 is particularly abundant in natto and plays a vital role in bone health and blood clotting. This nutrient is not commonly found in many foods, making natto a valuable dietary addition.

The protein content in natto supports muscle growth and repair, while its vitamin and mineral profile contributes to overall health and bodily functions.

The Fermentation Process

Natto fermentation transforms soybeans into a nutritious, probiotic-rich food through the action of Bacillus subtilis. This process involves specific stages and conditions that promote bacterial growth and enzymatic activity.

Role of Bacillus subtilis Natto

Bacillus subtilis Natto is the key microorganism responsible for natto fermentation. This beneficial bacterium produces enzymes that break down soybean proteins and carbohydrates. During fermentation, B. subtilis creates nattokinase, an enzyme with potential health benefits.

The bacteria also synthesize vitamin K2, which may support bone and cardiovascular health. As B. subtilis multiplies, it forms a characteristic sticky biofilm on the soybeans. This gives natto its unique texture and appearance.

To ensure successful fermentation, it’s crucial to use a pure culture of B. subtilis Natto. Commercial starters or a small amount of existing natto can provide the necessary bacterial inoculum.

Stages of Fermenting Natto

The natto fermentation process consists of several distinct stages:

1. Inoculation: Cooked soybeans are mixed with B. subtilis culture.
2. Initial growth: Bacteria begin to multiply rapidly.
3. Enzyme production: B. subtilis secretes various enzymes.
4. Protein breakdown: Soybean proteins are partially digested.
5. Biofilm formation: Bacteria create a sticky layer around the beans.
6. Aroma development: Characteristic natto smell develops.

Throughout these stages, the appearance, texture, and flavor of the soybeans change dramatically. The beans soften and develop a slippery coating. Their color may darken slightly.

Fermentation Time and Conditions

Proper fermentation conditions are essential for producing high-quality natto. The optimal temperature range is 37-40°C (98.6-104°F). This warm environment promotes rapid bacterial growth and enzyme activity.

Fermentation typically takes 18-24 hours. Shorter times may result in incomplete fermentation, while longer periods can lead to over-fermentation and undesirable flavors.

Humidity is another crucial factor. Natto requires high humidity (around 80-90%) to prevent the beans from drying out. Covering fermentation containers with breathable material like cloth or paper towels helps maintain moisture while allowing air circulation.

Oxygen is necessary for B. subtilis growth, so shallow containers are preferable to deep ones. This ensures adequate air exposure for the fermenting beans.

Preparing Soybeans for Natto

Proper soybean preparation is crucial for successful natto fermentation. The process involves careful selection, thorough cleaning, and precise cooking of the soybeans to create an ideal environment for fermentation.

Selecting the Right Soybeans

Choose high-quality, organic soybeans for optimal natto production. Small to medium-sized soybeans work best, as they ferment more evenly. Look for soybeans with a uniform color and smooth skin.

Avoid damaged or discolored beans, as they may affect the fermentation process. Some natto enthusiasts prefer using non-GMO soybeans to ensure a pure, traditional product.

Store dried soybeans in a cool, dry place to maintain their quality until use. Fresh soybeans are not suitable for natto production, so stick to dried varieties.

Washing and Soaking Techniques

Start by rinsing the dried soybeans under cold water to remove any debris or dust. Place the clean soybeans in a large bowl and cover them with water, using a 3:1 ratio of water to beans.

Allow the soybeans to soak for 12-24 hours at room temperature. This softens the beans and reduces cooking time. Change the water every 8 hours to prevent bacterial growth.

After soaking, drain and rinse the beans thoroughly. They should appear plump and slightly larger than their original size.

Cooking Soybeans for Fermentation

Cook the soaked soybeans until they’re soft enough to be easily squished between your fingers. Use one of these methods:

1. Stovetop: Boil the beans for 3-4 hours, adding water as needed.
2. Pressure cooker: Cook for 30-40 minutes at high pressure.
3. Slow cooker: Simmer on low for 6-8 hours.

Ensure the beans are fully cooked but not mushy. Overcooking can lead to a slimy texture in the final product.

Drain the cooked soybeans and let them cool slightly. They should be warm, not hot, when adding the natto starter culture.

Creating Homemade Natto

Fermenting natto at home requires specific equipment, careful preparation, and attention to detail. The process involves sterilizing tools, selecting the right ingredients, and creating an ideal environment for fermentation.

Gathering Necessary Equipment

A pressure cooker or large pot is essential for cooking soybeans. A yogurt maker or warm environment maintains the proper temperature for fermentation. Thermometers help monitor temperatures accurately. Sterilized containers, preferably glass or food-grade plastic, store the fermenting natto. Wooden or plastic spoons for stirring avoid metal contamination. A kitchen scale measures ingredients precisely. Clean cloths or paper towels cover containers during fermentation.

Sterilization and Cleanliness

Proper sterilization prevents unwanted bacteria growth. Boil all utensils, containers, and lids for 10 minutes. Allow them to air dry on clean towels. Wash hands thoroughly before handling ingredients. Use food-safe sanitizers on work surfaces. Avoid touching the natto mixture directly during fermentation.

Using a Natto Starter

Natto starter spores initiate fermentation. Commercial starters are available online or in specialty stores. Mix the starter with cooked soybeans according to package instructions. For a natural option, use a small amount of store-bought natto as a starter culture. Spread it evenly over the cooked beans. Some recipes suggest using bacillus subtilis spores directly.

The Fermentation Container

Choose a shallow, wide container for optimal fermentation. Glass or food-grade plastic work well. Avoid metal containers that may react with bacteria. Cover the container with a clean cloth or paper towel. Secure with a rubber band to allow air circulation while keeping contaminants out. Some prefer using aluminum foil with small holes poked for ventilation.

Place the container in a warm spot, ideally around 100-110°F (38-43°C). A yogurt maker or low-temperature oven maintains consistent warmth. Ferment for 24-48 hours, checking periodically for a sticky texture and characteristic aroma. Once fermented, refrigerate the natto to stop the process and enjoy.

Finishing and Serving Natto

Properly fermented natto develops a distinct sticky texture and stringiness. These characteristics, along with appropriate seasoning, contribute to the unique eating experience of this traditional Japanese food.

Assessing Fermentation and Stringiness

After the fermentation period, examine the natto for signs of successful fermentation. Well-fermented natto has a glossy appearance and a pungent aroma. Gently stir the natto with chopsticks to check for stringiness. The beans should form sticky, web-like strands when lifted.

If the natto lacks stringiness, it may need additional fermentation time. Continue fermenting for 4-6 more hours, checking periodically. Once the desired texture is achieved, refrigerate the natto to halt fermentation.

Store natto in an airtight container in the refrigerator. It typically keeps for up to a week.

How to Eat Natto

Natto is traditionally enjoyed over steamed rice. Place a serving of natto (about 2-3 tablespoons) on top of a bowl of rice. Mix thoroughly to distribute the sticky strands throughout the rice.

Some people prefer to eat natto on its own or with other accompaniments. Try spreading it on toast or adding it to salads for a protein boost.

Natto can be an acquired taste due to its strong flavor and unique texture. Start with small portions to acclimate to its distinctive qualities.

Seasoning and Adding Flavors

Natto is often seasoned to enhance its flavor profile. Common additions include:

• Soy sauce
• Mustard
• Chopped green onions
• Dried bonito flakes (katsuobushi)

Mix these ingredients with the natto before eating. Some commercial natto packages come with small packets of soy sauce and mustard.

For a modern twist, try adding natto to pasta dishes or using it as a topping for avocado toast. Experiment with different seasonings to find your preferred combination.

Natto powder, made from dried and ground natto, can be used as a seasoning or nutritional supplement. Sprinkle it on dishes or mix it into smoothies for added nutrients.

Preservation and Storage

Proper storage is crucial for maintaining natto’s quality and safety. Careful preservation techniques help extend shelf life while retaining flavor and nutritional benefits.

Storing Fresh Natto

Fresh natto requires refrigeration to slow bacterial growth and preserve its taste. Store natto in an airtight container between 35°F (2°C) and 41°F (5°C). At these temperatures, natto typically remains good for 1-2 weeks.

Keep natto away from strong-smelling foods to prevent odor absorption. Before consuming, allow refrigerated natto to sit at room temperature for 10-15 minutes to enhance its flavor and aroma.

For optimal freshness, consume natto within a few days of opening the package. Stir the beans thoroughly before eating to distribute the sticky strings evenly.

Freezing and Long-Term Preservation

Freezing is an effective method for long-term natto storage. Place natto in freezer-safe containers or bags, removing as much air as possible to prevent freezer burn.

Frozen natto can last several months without significant quality loss. Thaw frozen natto in the refrigerator overnight before use. Avoid refreezing thawed natto to maintain food safety.

For extended preservation, some natto enthusiasts dehydrate the fermented beans. Spread natto thinly on dehydrator trays and dry at 115°F (46°C) for 8-12 hours. Store dried natto in airtight containers in a cool, dark place for up to 6 months.

Alternatives and Variations

Natto fermentation offers room for creativity and experimentation. Innovative approaches allow for making natto without specialized equipment, using different legumes, and incorporating natto into various recipes.

Making Natto without Specialized Equipment

Homemade natto can be produced using common household items. A large glass jar or plastic container can substitute for specialized fermentation equipment. To maintain the required temperature of 95-108°F (34-42°C), wrap the container in a heating pad or place it in a warm spot like near a radiator.

For those without natto starter, backslopping is an option. This involves using a small amount of store-bought natto to inoculate the next batch. Simply mix a teaspoon of prepared natto with cooked soybeans before fermentation.

A DIY incubator can be created using a cooler or insulated box. Place a hot water bottle inside to maintain warmth. Monitor the temperature with a thermometer to ensure optimal conditions for natto-kin growth.

Trying Different Beans and Peas

While soybeans are traditional, natto can be made with other legumes. Black beans, chickpeas, and adzuki beans offer unique flavors and textures. These alternatives may require adjusted cooking and fermentation times.

Experiment with lentils for a quicker-cooking option. Green or brown lentils work well and typically ferment faster than larger beans. Split peas are another interesting choice, producing a softer texture.

For a protein-packed variation, try using lupini beans. These require thorough soaking and cooking before fermentation. Mung beans create a milder-tasting natto that’s less sticky than soybean versions.

Alternative Natto-Based Recipes

Natto’s versatility extends beyond traditional serving methods. Blend it into smoothies for a probiotic boost. Mix with avocado for a nutrient-rich spread on toast or crackers.

Create a savory natto dip by combining it with Greek yogurt, garlic, and herbs. This makes an excellent accompaniment for vegetables or chips. For a twist on hummus, blend natto with chickpeas, tahini, and lemon juice.

Incorporate natto into baked goods for added nutrition. Mix it into bread dough or muffin batter. The fermentation process helps break down anti-nutrients, making the beans more digestible.

Try natto fried rice by stirring it into cooked rice with vegetables and seasonings. For a cold dish, toss natto with chilled soba noodles, green onions, and a soy-based dressing.