How to make tempeh at home
Hulled, cooked soybeans, a bought culture and a day or two of warmth. What makes it work, what protects it, how to incubate it and how to tell it's right, with the figures from the guides.
8 min read Advanced Reviewed October 26, 2026 52 facts, each with its source
What tempeh is
Tempeh comes from Java, in Indonesia: it's first mentioned in a 17th-century manuscript1, and it's the only soy ferment that didn't originate in China or Japan2. It's a compact white cake of hulled, cooked soybeans, fermented with a mold, Rhizopus3. The mold's threads are what bind the beans into a cake4.
Unlike almost every other ferment, tempeh doesn't turn sour. Rhizopus releases ammonia into the beans5, and the pH rises from 4 to 76. At the end there's no acidity to protect it: the protection lies in what you do before and during.
Four rules that never change
- Always cooked before eating. Uncooked tempeh is handled as raw food7. In 2012, in the United States, a Salmonella outbreak came from unpasteurized tempeh and a contaminated culture8. That's why the guides ask for raw tempeh to be labeled as needing cooking9.
- Bought culture only. A Rhizopus culture from an approved supplier10, and never tempeh from another batch to get started11. Many wild Rhizopus strains carry bacteria that make toxins12.
- Never corn or coconut. In Indonesia, coconut tempeh, tempe bongkrek, caused many bongkrekic acid outbreaks13. The toxin isn't removed by washing or cooking14, and some outbreaks killed up to 60% of those affected15. Singapore's food agency says not to ferment corn or coconut at home16.
- A cold, acid soak. More than 4 to 6 hours of uncontrolled soaking lets bacteria with heat-resistant toxins grow, such as Bacillus cereus and Staphylococcus aureus17. Fervida soaks in the fridge and with vinegar, and adds vinegar to the cooking water too (our house rule).
Hulling and soaking
Use split, hulled soybeans: with the hull on, the mold can't get into the bean18. If yours are whole, the hulls float during soaking and come off more easily19.
The soak lasts 6 to 24 hours20, and it has to be acid or in the fridge21. For small batches, the guide accepts the fridge alone22, but Fervida does both: a soak in the fridge with 0.25% acetic acid in the water23, about 50 ml (3½ tablespoons) of store-bought 5% vinegar per liter, which is our own calculation. With a meter, the water should read between pH 3.5 and 4.624.
The reason is what happens after the soak. Without acid, Bacillus cereus can reach millions per gram in 40 hours of fermentation25, and cooking the tempeh afterward doesn't remove one of its toxins, cereulide26. And it isn't just soybeans: the same pathogens grow without acid in chickpea, pea or fava bean tempeh27.
Cooking, drying and cooling
Throw out the soaking water and boil the soybeans for 20 to 30 minutes28. Fervida adds vinegar to the cooking water too, in the same proportion as the soak (our house rule): in one study, the acid cut down Bacillus spores29.
Drain them well and dry the outside with clean towels30. If they stay too wet, spoilage microbes and harmful bacteria grow31.
Then spread them out to cool to 25–37 °C (77–99 °F)32. Once they drop below 60 °C (140 °F), they need to get there within 2 hours33, and the limit is 634. If it takes longer, they go (a house rule).
Incubating: heat, air and humidity
Sprinkle on the culture at the dose on the package and mix well. Spread the beans in perforated plastic bags, or in trays covered with perforated plastic35. They have to drain: the beans can't sit in water36.
The mold needs air, but not too much: with lots of oxygen it forms spores37. The right humidity is between 75 and 85%38, and closed, perforated bags hold it.
The guides give 1 to 3 days at 20–37 °C (68–99 °F)39. The warmer it is, the shorter the time40:
| Temperature | Time |
|---|---|
| 25 °C (77 °F) | About 80 hours: it's slow, which is why Fervida incubates at 30–32 °C (86–90 °F) |
| 32 °C (90 °F) | About 22 hours |
| 35 °C (95 °F) | About 18 hours |
Fervida incubates at 30–32 °C (86–90 °F). As the mold grows, the cake warms itself by 5 to 7 °C (9 to 13 °F), so the spot shouldn't go above 37 °C (99 °F)41. Inside, never above 42 °C (108 °F): the mold dies and others grow42. If it reaches 40 °C (104 °F), separate the bags and give them air; if it went above 42 °C for more than an hour, throw it out; and if there's no cake at 48 hours at 30–32 °C (86–90 °F), the same. Those are house rules.
When it's done
Good tempeh is white, covered in abundant mold43, compact, and doesn't crumble when cut44. It tastes nutty, meaty and like mushrooms45, and smells of fresh tempeh, with no ammonia46.
A few black or gray spots by the holes are the mold's spores. If fermentation goes on too long, the surface turns black and the ammonia smell rises47. BCCDC treats it as a quality defect48; even so, if the ammonia smell is strong, see "It smells like ammonia" before eating it.
Yellow, pink, orange, green or blue; wet, soft or slimy patches; a sour or rotten smell: it all goes, and that's a house rule. It's explained in "Black spots on tempeh" and "It smells like ammonia."
Storing and cooking
Take the tempeh out of the bags and let it lose its heat on a rack. Fresh tempeh keeps 24 to 72 hours49; at Fervida, raw and in the fridge, 3 days at most (a house rule). Kept raw for a long time, it smells of ammonia and turns black50.
To keep it longer, steam, boil or fry it51, then refrigerate or freeze it. Cooking stops the mold: no more spores, no more ammonia smell52.
It's always eaten cooked: seared, fried, baked or steamed.
The recipes
- Homemade tempeh: hulled soybeans and a bought culture. The starting point.
- Chickpea tempeh: the same method, with the same soak, cooking and cooling.
Don't mix grains such as rice or barley in with the beans: they bring their own bacteria, and there are no figures for doing it at home (a house rule).
Where every number comes from
Every number in the text leads to its figure: the exact sentence from the official guide it comes from, in its own language.
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1
Tempeh is first mentioned in a 17th-century manuscript from Java
“The earliest mention of tempeh was in a manuscript dating back to the 1600’s in Java, Indonesia.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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2
It's the only soy ferment that didn't originate in China or Japan
“Tempeh is the only fermented soy product that did not originate in either China or Japan.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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3
A compact white cake of hulled, cooked soybeans fermented with Rhizopus
“Tempe is a compact, white, cake-form product, prepared from dehulled boiled soybeans through solid state fermentation with Rhizopus spp.”
Codex Alimentarius Commission (FAO/WHO) · Regional Standard for Tempe (CODEX STAN 313R-2013, amended 2015) · read on October 25, 2026
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4
The mold's threads bind the beans into the cake
“Mould strands (or fungal hyphae or mycelia) are the binding agent that holds the digested soybeans in the tempeh cake together.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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5
Rhizopus releases ammonia into the beans
“Tempeh is described as an alkaline fermentation because the main fermenting agents are Rhizopus spp. that release ammonia into the soybeans.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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6
pH rises from 4 to 7
“This is an alkaline fermentation, pH increases from pH 4 to pH 7 during the process.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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7
Uncooked tempeh is handled as raw food
“Safe handling of uncooked, unpasteurized tempeh should be emphasized for prevention of foodborne illnesses.”
CDC, Emerging Infectious Diseases (Griese S.E. et al.) · Gastroenteritis Outbreak Associated with Unpasteurized Tempeh, North Carolina, USA (2013) · read on October 25, 2026
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8
An outbreak from unpasteurized tempeh and a contaminated culture
“we identified unpasteurized tempeh as a novel food vehicle and Rhizopus spp. starter culture as the source of the contamination”
CDC, Emerging Infectious Diseases (Griese S.E. et al.) · Gastroenteritis Outbreak Associated with Unpasteurized Tempeh, North Carolina, USA (2013) · read on October 25, 2026
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9
If it's raw, the label must say it needs cooking
“If the product is raw, labelling on packaging should indicate a cook step is required,”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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10
Rhizopus culture from an approved supplier
“Use of commercial Rhizopus culture from an approved supplier.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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11
No starting from an earlier batch of tempeh
“Backslopping using previous tempeh and Rhizopus mould is not”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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12
Many wild Rhizopus strains carry bacteria that make toxins
“Many wild strains of Rhizopus species can harbour species of bacteria that produce toxins.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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13
In Indonesia, coconut tempeh caused bongkrekic acid outbreaks
“In Indonesia, tempeh made with coconut milk and coconut cake contaminated with a mitochondrial toxin, bongkrekic acid caused”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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14
Bongkrekic acid isn't removed by washing or cooking
“Bongkrekic acid cannot be destroyed by washing or cooking.”
Singapore Food Agency · Bongkrekic Acid: Safety of Fermented Corn and Coconut Products · read on October 25, 2026
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15
Some outbreaks killed up to 60% of those affected
“previous outbreaks have resulted in a high mortality rate of up to 60 percent.”
Centre for Food Safety, Food and Environmental Hygiene Department, Hong Kong · Food Safety Focus (213rd Issue, April 2024): Bongkrekic Acid – Uncommon but Fatal Toxin in Certain Foods · read on October 25, 2026
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16
Don't ferment corn or coconut at home
“Avoid fermenting corn or coconut milk/pulp products at home as dedicated facilities and/or processes under strict hygiene practices are required to mitigate the risk of Bongkrekic acid contamination.”
Singapore Food Agency · Bongkrekic Acid: Safety of Fermented Corn and Coconut Products · read on October 25, 2026
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17
Over 4 to 6 hours of uncontrolled soaking lets bacteria with heat-resistant toxins grow, such as Bacillus cereus and Staphylococcus aureus
“When soybeans or other substrates are soaked for longer than 4 to 6 hours, bacteria capable of producing heat resistant toxins have the opportunity to grow, such as Bacillus cereus and Staphylococcus aureus.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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18
Hulled, so the mold can get into the bean
“The removal of the husks from soybeans is required for mould culture to penetrate the bean.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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19
When soaking, the hulls float and come off more easily
“Soaking can make it easier to remove husks that float to the top of water”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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20
Soak 6 to 24 hours
“Once beans are de-hulled, the next step is to soak the soybeans for 6 to 24 hours.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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21
An acid soak or one in the fridge
“CHECK: Soaking step must be done in acidified or refrigerated”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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22
For small batches, soaking in the fridge works
“Refrigeration during soaking is also acceptable when small batches of tempeh are made.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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23
0.25% acetic acid in the soaking water
“Acidulants, such as 0.5% to 0.85% lactic acid or 0.25% acetic acid per litre of water are recommended”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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24
Soaking water between pH 3.5 and 4.6
“Acidification of water with acetic or lactic acids to pH of 4.6 or lower, but not below pH of 3.5”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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25
Without acid, Bacillus cereus reaches millions per gram in 40 hours
“However, if no acidification occurs during soaking, pathogens, e.g., Bacillus cereus, can grow to log 6 to log 7 CFU/g after 40 hr fermentation.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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26
Cereulide, a Bacillus cereus toxin, isn't destroyed by boiling
“if heat stabile toxin is formed (e.g., cereulide toxin formed from Bacillus cereus) these are not destroyed by boiling.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.10: Koji foods: miso, soy sauce and amazake (September 2023, updated December 2024) · read on October 25, 2026
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27
Without acid, the same pathogens grow on soybeans, chickpeas, peas or fava beans
“Other pathogens modelled in tempeh that also grow in unacidified tempeh substrates (soybean, chickpea, pea, fava bean tempeh) include E. coli, L. monocytogenes and S. aureus.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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28
Boiled 20 to 30 minutes, the soaking water thrown away
“Soak water is discarded and soybeans are boiled for 20 to 30 minutes, ranging from 10 min to 3 hrs.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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29
Acid in the cooking water, fewer Bacillus spores
“One study suggests adding acid to the boiling water also appears to reduce occurrence of Bacillus spores during the cook step.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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30
The surface of the beans dried with towels
“surface drying of soybeans (e.g., coating beans with wheat flour or drying with towels)”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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31
Too wet, spoilage microbes and harmful bacteria grow
“If conditions during fermentation are too wet, spoilage microbes and/ or harmful bacteria may grow.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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32
Cooled to 25–37 °C before the culture goes in
“cooled to between 25oC and 37oC prior to”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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33
Cooled within 2 hours
“Cooling to the target mould inoculation temperature (e.g., <38oC) should occur within 2 hrs”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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34
Once below 60 °C, 6 hours as the limit
“after temperatures fall below 60oC (ideal) with critical limits of up to a maximum of 6 hrs.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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35
Perforated plastic bags, or trays covered with perforated plastic
“Commonly, perforated polyethylene plastic pouches are used, however perforated plastic can also be used to cover the tops of wooden, plastic, or stainless steel containers.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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36
It must drain: the beans can't sit in water
“Containers should drain as tempeh soybeans should not be held in standing water”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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37
Enough oxygen, but not too much, or it forms spores
“The fermentation conditions and packaging should allow for sufficient oxygen, but not too much oxygen, otherwise sporulation will occur.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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38
The right humidity is 75 to 85%
“Optimal humidity is between 75 and 85%.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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39
1 to 3 days at 20–37 °C
“conditions may vary from 1 to 3 days at temperatures between 20oC to 37oC.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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40
About 80 hours at 25 °C, 22 at 32 °C and 18 at 35 °C
“Example conditions are 25oC for 80 hrs; 35oC for 18 hr; 32oC for 22 hr and others.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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41
The cake warms up 5 to 7 °C: incubate at 37 °C or below
“As temperature may rise between 5oC to 7oC, fermentation temperatures at or below 37oC or lower is”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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42
Above 42 °C the mold dies and others grow
“Temperatures should not go above 42oC as Rhizopus mould may die off, permitting growth of spoilage organisms.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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43
White, covered in abundant mold
“(b) Colour: White colour of luxurious growth of mycellium of Rhizopus spp.”
Codex Alimentarius Commission (FAO/WHO) · Regional Standard for Tempe (CODEX STAN 313R-2013, amended 2015) · read on October 25, 2026
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44
Compact, doesn't crumble when cut
“(a) Texture: Compact and not easily disintegrated upon cutting with knife.”
Codex Alimentarius Commission (FAO/WHO) · Regional Standard for Tempe (CODEX STAN 313R-2013, amended 2015) · read on October 25, 2026
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45
Tastes nutty, meaty and like mushrooms
“(c) Flavour: Characteristic of tempe flavour, nutty, meaty, and mushroom-like.”
Codex Alimentarius Commission (FAO/WHO) · Regional Standard for Tempe (CODEX STAN 313R-2013, amended 2015) · read on October 25, 2026
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46
Smells of fresh tempeh, with no ammonia
“(d) Odour: Characteristic of fresh tempe odour without ammonia smell.”
Codex Alimentarius Commission (FAO/WHO) · Regional Standard for Tempe (CODEX STAN 313R-2013, amended 2015) · read on October 25, 2026
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47
Left too long, it turns black and the ammonia smell rises
“If the alkaline fermentation goes too long, surface discolouration will result from the white mould on the surface turning black due to formation of spores, and an over-production of ammonia odour.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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48
BCCDC treats it as a quality defect
“If the alkaline fermentation goes too long, surface discolouration will result from the white mould on the surface turning black due to formation of spores, and an over-production of ammonia odour. While this is not a safety issue, it is an undesirable food quality issue.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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49
Fresh tempeh keeps 24 to 72 hours
“Fresh tempeh has a shelf life of 24 to 72 hrs.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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50
A long time in the fridge brings an ammonia smell and black spores
“Prolonged refrigerated storage of fresh tempeh can result in undesirable odour from the ammonia smell and growth of black coloured Rhizopus mould when it sporulates.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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51
Steamed, boiled or fried, it keeps longer
“Shelf life can be extended by steaming, boiling, or frying.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.9: Tempeh (November 2023, updated December 2024) · read on October 25, 2026
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52
Cooking stops the mold, the ammonia smell and the spores
“These processes will inactivate the mould hyphal strands from growing to excess and producing an ammonia-like odour, and stop the mould from sporulating and forming black-coloured spores unsightly to consumers.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 2: Starter cultures and fermented food standards (August 2024, updated December 2024) · read on October 25, 2026