Soy & legumes ferment
Tempeh
Cooked, acidified soybeans bound into a firm cake by white Rhizopus mycelium in 24–48 hours.
- Temperature
- 29–33 °C
- Overheating above about 35 °C kills the mould and favours bacteria.
- Time
- 24–48 hours
- Stop when bound into a firm white cake.
Timeline
Stage 1: Soak, dehull, cook, acidifystart · about 14 h
Hands-on
Stage 2: Incubatefrom 14 h · about 36 h
Fermenting / waiting — 30–32 °C
Stage 3: Refrigeratefrom 2 days · keeps about 7 days
Cold storage — Up to about a week; or freeze
Ingredients
- Dehulled soybeans
- Vinegar to acidify (follow the starter supplier's amount)
- Tempeh starter (commercial)
Equipment
- Pot
- Clean towels
- Perforated bags or containers
- Incubator holding 30–32 °C (e.g. oven with light, proofing box)
- Thermometer
Steps
- Soak, dehull and cook the beans until just tender, adding vinegar as the starter instructions say.
- Drain and dry the beans well; cool to body temperature.
- Mix in the starter thoroughly.
- Pack about 2–3 cm thick in perforated bags or trays.
- Incubate at 30–32 °C for 24–48 hours; it gets warm itself after ~12 hours — prevent overheating.
- When fully white and firm, refrigerate. Cook before eating.
Is it working?
- Solid white cake that holds together when sliced
- Mushroomy, nutty smell
Smell & texture: Mushroomy, nutty, a little yeasty. Small grey-black patches near air holes are spores (normal).
Signs tell you it's fermenting, not that it's safe: never rely on smell or appearance alone.
Safety, mould and discard rules
Mould or yeast?
Here the white mould IS the food: dense, white, even mycelium is right, and black-grey sporing near holes is normal. Any other colour, sliminess or a bad smell: discard.
Storage
Refrigerate or freeze. Always cook tempeh before eating.
Shelf life: About a week in the fridge; months frozen.
The science: what's happening
Spores of the mould Rhizopus grow white threads (mycelium) through cooked beans, knitting them into a cake and making them more digestible. Acidifying the beans first holds back harmful bacteria while the mould gets going.
Organisms
- Rhizopus oligosporus / Rhizopus microsporus (commercial starter)
Troubleshooting
- Didn't bind
- Too cool, too wet or too little starter.
- Wet and smelly
- Beans not dried or overheated: discard.
A dish (not a ferment) gone wrong? Try Recipe Rescue.
Cook with it
Learn more
Sources
- Critical Parameters for the Safe Production of Tempeh (P2-207) — International Association for Food Protection, 2015 annual meeting
- Potential Hazards with Fermented Foods — Association of Food and Drug Officials
Guidance changes: check the source for current wording. Original text; figures quoted from the sources where stated.