Natto is a traditional Japanese fermented soybean food. It is made by fermenting cooked soybeans with Bacillus subtilis var. natto. The result is famous for its sticky, stringy texture, distinctive aroma and savoury flavour.
If you are in India and want to make natto yourself, the basic idea is straightforward: cook soybeans thoroughly, inoculate them with a natto starter culture, keep them warm and oxygen-accessible during fermentation, then chill the finished natto.
What exactly is natto?
Natto is not a sauce, seasoning or capsule. It is a whole-food fermentation made from soybeans. During fermentation, the starter microorganism grows on the cooked beans and produces the characteristic extracellular polymers that make good natto stretch into fine strings when stirred.
That texture is not a defect. If your finished beans are sticky and stringy, you have one of the classic visual signs of a successful natto fermentation.
What is natto starter culture?
Natto starter culture is the microorganism used to start the fermentation. For this product, the culture is Bacillus subtilis var. natto.
A starter is useful because it gives you a defined organism to inoculate the cooked soybeans rather than relying on whatever microorganisms happen to be present in the environment. That makes the process much more repeatable for home fermentation.
See the Zoh Probiotics Natto Starter Culture.
How is natto made?
The home process can be thought of as six stages:
- Soak: hydrate the dry soybeans thoroughly.
- Cook: cook until the beans are tender enough for fermentation.
- Inoculate: introduce the natto starter to the cooked beans using a clean process.
- Ferment: hold the inoculated beans at a warm fermentation temperature, typically around 40–43°C.
- Chill: refrigerate the fermented beans so the process slows and the flavour develops.
- Eat: stir and serve the natto in the way you prefer.
How long does natto fermentation take?
A typical home fermentation takes roughly 22–24 hours when the beans are held around 40–43°C. Actual results can vary with starter amount, bean preparation, vessel design, temperature stability and other process variables.
The important point is consistency. A fermentation chamber that fluctuates significantly can produce different results from batch to batch, even when you use the same starter.
Why is natto sticky?
The characteristic strings are part of the fermentation. When properly fermented, natto develops a noticeably viscous, stringy matrix that becomes especially obvious when you stir the beans.
So: sticky is expected. A little strange-looking is expected. Natto is not supposed to behave like ordinary boiled soybeans.
What does natto taste and smell like?
Natto has a distinctive fermented aroma that some people find nutty, earthy or savoury and others find intense at first. The flavour is generally savoury and fermented rather than sweet.
There is a learning curve. If you are trying natto for the first time, start with a small serving and pair it with familiar foods such as rice, spring onion, mustard, soy sauce or other savoury toppings.
Natto vs tempeh: are they the same?
No. Both are fermented soybean foods, but they use different microorganisms and produce very different finished foods.
- Natto: fermented with Bacillus subtilis var. natto; soft beans; characteristic sticky strings.
- Tempeh: commonly fermented with Rhizopus species; beans become bound into a firm cake.
Natto is therefore not simply a Japanese version of tempeh. The fermentation organism, texture and eating experience are different.
Can you make natto at home in India?
Yes. The core requirement is not a special country-specific ingredient; it is a reliable fermentation process. You need soybeans, a suitable natto starter culture, clean equipment and a way to maintain the fermentation temperature consistently.
In India, ambient temperatures can be useful during some parts of the year, but they are not necessarily stable enough for repeatable results. A controlled warm environment can make the process easier to reproduce.
What can make a batch fail?
Common problems include temperatures that are too low or unstable, poor hygiene, overfilling the fermentation vessel, unsuitable containers, insufficient aeration, or using a process that does not give the culture the conditions it needs.
If the beans remain completely non-sticky, show no expected fermentation characteristics, or develop an unusual appearance or odour that concerns you, do not assume the batch is successful simply because time has passed. Fermentation is a process, not a timer.
Natto starter culture: how much do you need?
The Zoh Probiotics starter is supplied as 5 sachets × 5g. Following the recommended process, each sachet is intended for up to approximately 500g of soybeans, giving up to about 2.5kg of soybeans across the five sachets.
Those are process capacities, not guarantees of finished yield. Your actual finished batch depends on the beans and fermentation method you use.
Is natto the same thing as nattokinase?
No. Natto is the fermented food. Nattokinase is an enzyme associated with natto and has been studied separately in scientific research. They should not be treated as interchangeable product categories.
That distinction matters when buying a starter culture: you are buying a fermentation ingredient intended to help you make food, not a nattokinase supplement.
What about vitamin K2?
Natto is well known in nutrition research for its vitamin K content, including forms of vitamin K2. The amount present in a finished batch can depend on the fermentation process and other factors.
For a home ferment, it is better to think of this as a food-quality and nutrition topic rather than making medical promises about what natto will do for you.
How should beginners approach their first batch?
Keep the first batch simple. Follow one consistent process, record the soybean quantity and fermentation temperature, and change only one variable at a time when you experiment.
Once you have a reliable baseline, you can start testing different soybean varieties, batch sizes, fermentation vessels and serving styles.
Ready to make your own?
If you want to start with a defined natto culture rather than trying to capture a microorganism from an existing batch, shop the Zoh Probiotics Natto Starter Culture.
It contains Bacillus subtilis var. natto and comes as five 5g sachets, with each sachet intended for up to 500g of soybeans when the recommended process is followed.