Make authentic Japanese natto at home.
This starter culture contains Bacillus subtilis var. natto, the microorganism used to ferment cooked soybeans into natto. The freeze-dried culture is supplied as 5 sachets × 5g; each sachet is intended for up to 500g of soybeans when following the recommended process.
How to make natto
- Soak and cook the soybeans until they are thoroughly tender.
- Work with clean, sanitised equipment and handle the cooked beans while they are still warm.
- Inoculate the beans using one sachet according to the included instructions.
- Ferment at approximately 40–43°C for 22–24 hours, using a setup that maintains stable temperature and allows appropriate airflow.
- After fermentation, refrigerate the natto before eating. Chilling helps develop the characteristic texture and flavour.
What successful natto looks like
Properly fermented natto develops the characteristic sticky, stringy texture associated with the food and a distinctive fermented aroma. Fermentation speed can vary with bean preparation, temperature, inoculum and equipment.
Troubleshooting
- No stringiness: check fermentation temperature, bean tenderness, inoculation and whether the culture was handled according to instructions.
- Beans are still hard: the substrate was not cooked sufficiently. Cooking is part of the fermentation process, not a step to shortcut.
- Strongly abnormal colour, mould or putrid odour: discard the batch rather than tasting or trying to rescue it.
- Temperature fluctuated: use a thermometer and a more stable fermentation setup on the next batch.
Learn more
Read our complete guide to natto and home fermentation. For the wider fermentation context, see the Fermentation Cultures hub. For Zoh's evidence-led approach to live cultures, see The Science of Live Cultures.
Important
Natto is a fermented food, not a medicine. This page focuses on fermentation technique and product information rather than making disease-treatment claims.
