How to Make Tempeh
Tempeh is an Indonesian fermented soybean cake made by inoculating cooked soybeans with Rhizopus oligosporus mold. The mold binds the beans into a firm, sliceable cake with a nutty, earthy flavor and meaty texture.
Category: Legumes & Soy · Method: Fungal/Mold · Time: 24-48h · Difficulty: 3/5 · Yield: ~500g · Temp: 30-32°C
History
Tempeh originated in Java, Indonesia, several centuries ago. It became a staple protein source in Indonesian cuisine and has gained worldwide popularity as a nutritious plant-based protein. Traditional tempeh is wrapped in banana leaves.
Ingredients
- 500g Dried soybeans — Dehulled and split soybeans are recommended for beginners to ensure mycelium can easily access the bean interior.
- 1 tsp Tempeh starter — Rhizopus oligosporus spores
- 2 tbsp White vinegar — Lowers pH to favor the mold
Equipment
- Large pot for cooking beans
- Colander
- Clean towels for drying
- Perforated plastic bags or banana leaves
- Incubator or warm spot (30-32°C)
- Thermometer
Instructions
Soak soybeans
Cover soybeans with several inches of water. Soak for 12-24 hours. If using whole beans, they will double in size. For easier processing, use pre-split beans or roughly crack whole beans before soaking.
Time: 12-24 hours
Tip: Change water once or twice if soaking longer than 12 hours to prevent unwanted bacterial fermentation.
Dehull and split beans
Rub beans vigorously between hands or in a towel to loosen hulls and split the beans into halves. Float off hulls by adding water - hulls will rise to the surface. It is essential that the beans are split so the mold can penetrate the starch.
Time: 20-30 min
Tip: Removing hulls and splitting the beans is the most important step for a firm, successful cake.
Dry beans thoroughly
Drain beans well. Spread on clean towels and pat dry, or use a hair dryer on a cool setting. Let cool to below 35°C. Beans must be completely surface-dry to the touch before inoculation to prevent 'sweating' and bacterial spoilage in the bags.
Time: 30 min
Tip: If the beans feel tacky or wet, they are not ready. Excess moisture is the #1 cause of tempeh failure.
Fermentation Timeline
- Hour 0-12: Incubation begins — No visible changes. Spores are germinating.
- Hour 12-24: White spots appear — First signs of mycelium growth between beans.
- Hour 24-36: Mycelium spreads — White fuzz covers beans. Cake begins to hold together.
- Hour 36-48: Tempeh ready — Dense white mycelium completely binds beans. Cake is firm and sliceable.
Signs of Success & Spoilage
Good signs
- White, cotton-like mycelium covering
- Beans firmly bound together into a solid cake
- Pleasant mushroomy, nutty, or yeasty smell
- Slight warmth from the cake (active fermentation)
- Small patches of gray or black spores, especially near air holes (normal maturation)
Warning signs
- Brightly colored mold (green, orange, or yellow)
- Slimy, fuzzy black patches (distinct from flat gray/black Rhizopus spores)
- Strong ammonia or putrid, rotten smell
- Slimy or wet texture on the bean surface
- Beans falling apart easily after 48 hours
Troubleshooting
- Beans not binding
- Cause: Too wet, too cold, or dead starter Solution: Ensure beans are dry. Maintain 30-32°C. Use fresh starter.
- Black spots
- Cause: Rhizopus sporulation (usually OK) or contamination Solution: Black Rhizopus spores are safe. Other colors indicate contamination - discard.
- Ammonia smell
- Cause: Over-fermented or contaminated Solution: Reduce fermentation time. Ensure proper temperature control.
- Uneven growth
- Cause: Poor starter distribution or uneven temperature Solution: Mix starter more thoroughly. Ensure consistent incubator temperature.
Storage
Wrap tightly and refrigerate immediately after fermentation stops. Keeps 1 week refrigerated, 3 months frozen. Slice and freeze portions for longer storage. Thaw before cooking.
Health Benefits
- Complete plant-based protein source
- High in dietary fiber
- Rich in vitamins B2 and B6
- Contains trace B12 (Note: B12 levels vary by strain and should not be a primary source for vegans)
- Good source of iron and calcium
- Contains prebiotics and is easier to digest than unfermented soy
Serving Suggestions
- Slice and pan-fry until crispy
- Marinate and grill or bake
- Crumble into stir-fries
- Use in sandwiches and wraps
- Add to curries and stews
- Tempeh bacon
Related Legumes & Soy Ferments
Other Fungal/Mold Ferments
- Miso — Condiment
- Furu (tofu cubes) — Legumes & Soy
- Tempeh gembus — Legumes & Soy
- Stinky tofu — Legumes & Soy
- Blue cheese — Dairy
- Brie — Dairy
- Camembert — Dairy
- Roquefort — Dairy