Tempeh is a firm cake of cooked soybeans bound together by the white, cottony growth of a mold, usually Rhizopus (often sold as R. oligosporus). It comes from Java, Indonesia. As the mold grows through the beans over a day or two, its enzymes break down soybean proteins, fats and starches, giving tempeh its nutty, mushroomy flavor and firm, sliceable texture, and reducing some of the beans’ antinutrients (Hachmeister & Fung, 1993). It’s always eaten cooked – fried, baked, steamed or crumbled.
What’s in Tempeh
Per 100 g, Japan’s food tables list tempeh at 15.8 g protein, 70 mg calcium, 2.4 mg iron and just 11 µg vitamin K – far less vitamin K than natto – and no vitamin B12 was found (MEXT). So tempeh is a good plant protein, but not a B12 source. Because it’s cooked, it isn’t a probiotic food either. Compare it with other soy ferments in our fermented soybean guide. Indonesia’s oncom applies mould fermentation to okara and peanut press cake.
The Method in Brief
- Soak soybeans 8–24 hours, then dehull them by rubbing in water and skimming off the skins – hulls block the mold.
- Cook the split beans until tender but not mushy (45–60 minutes). Many makers add a splash of vinegar to the cooking water to acidify the beans slightly.
- Dry and cool thoroughly: wet beans are the main cause of slimy, failed tempeh. Cool to below 35°C.
- Inoculate with tempeh starter and mix well.
- Pack 2–3 cm thick into perforated bags or banana leaves – the mold needs air.
- Incubate at 29–32°C for 24–48 hours. The tempeh starts making its own heat after about a day, so keep it from going above about 38°C.
The recipe card below has quantities. Tempeh can also be made from other beans or with grains – a review of tempeh-like products found that red sorghum worked well with Rhizopus while some grains crumbled (Hachmeister & Fung, 1993) – add a spoonful of rice flour for low-starch beans such as black beans or chickpeas.
Is It Safe?
- Use a reputable starter and cook your tempeh. In 2012, an outbreak of Salmonella Paratyphi B infections in North Carolina was traced to unpasteurized tempeh, and the contamination came from the Rhizopus starter culture itself (Griese et al., 2013). Homemade tempeh is raw until you cook it.
- Know the good and bad colors. White mycelium is the tempeh; grey or black patches near air holes are the mold making spores and are normal. Green, blue, pink, orange or yellow growth, sliminess, or a sour, rotten or strong chemical smell mean discard it.
- Never make tempe bongkrek. Tempe bongkrek, made with coconut, can be contaminated by Burkholderia gladioli pv. cocovenenans, whose heat-stable toxin, bongkrekic acid, has also been linked to fermented corn products and rice noodles; case fatality in outbreaks has ranged from 30% to 100% (Yang et al., 2026). Stick to beans and grains.
More bean ferments, and which ones are risky at home: fermented beans; for the bacterial soybean ferment, natto.
