Tempeh

Tempeh

Tempeh (in Hebrew “טמפה”) comes from the island of Java in Indonesia, where it has been a staple food for hundreds of years.

Tempeh is partially cooked soybeans fermented with the mold Rhizopus oligosporus. The mold sends out white threads of mycelium that grow between the beans and bind them into a solid “cake” that can be sliced. This is the structural difference from tofu, and it explains nearly all of the nutritional differences between them.

The key distinction: tofu is made much like cheese — the soybeans are ground into a drink, the liquid is curdled, and the solids are pressed into a mold. Along the way, the fiber and hulls are filtered out. In tempeh, by contrast, the bean stays whole. Nothing has been taken out of it — something has only been added.

Nutrition facts

*Depends entirely on the coagulant — see tofu.

The standout figures: tempeh provides more protein than tofu (20.3 vs. 15-17 grams) and six to twenty times as much fiber — because the bean stays whole.

What fermentation does — the real advantage

This is the heart of the matter, and it is usually presented vaguely (“fermentation is healthy”). The mechanism is specific and can be explained:

• Breaking down phytic acid. The Rhizopus mold secretes the enzyme phytase, which breaks down the phytic acid in the bean. Phytic acid binds iron, zinc and magnesium and prevents their absorption. Measurements have found a significant drop in phytate content during fermentation — meaning the minerals in the table above are more available to the body than in the same amount of unfermented soy. This is tempeh’s clearest nutritional advantage.

• Partial breakdown of proteins and fats. The mold’s protease and lipase enzymes break some of the protein down into peptides and free amino acids. The result: better digestibility and a contribution to umami flavor.

• Breaking down oligosaccharides. Fermentation breaks down some of the raffinose and stachyose — the sugars responsible for gas and bloating from legumes. That is why many people describe tempeh as easier to digest than whole soybeans.

• Isoflavones in free form. Fermentation converts isoflavones from the glucoside form (bound to sugar) into the aglycone — the free form, which is absorbed faster and more efficiently.

Vitamin B12 in tempeh — the most important warning

This is the critical point on this page, and it is a widespread mistake online: do not rely on tempeh as a source of vitamin B12.

The background: old measurements found B12 in traditional tempeh. But the Rhizopus mold does not produce B12 at all — only bacteria produce it. The B12 that was found came from random bacterial contamination during village-scale production (strains of Klebsiella and Citrobacter).

That leads to three problems:

1. Complete inconsistency. The amount depends on chance contamination and varies by orders of magnitude from batch to batch.
2. Commercial tempeh is made under controlled hygienic conditions — and therefore usually contains negligible to zero amounts.
3. Inactive analogs. Some of what was measured with old microbiological methods is B12-like corrinoids that are inactive in the human body and may even compete for binding sites.

The practical conclusion: vegans need a reliable source of B12 — a supplement or fortified food. Tempeh, natto, miso, seaweed and spirulina are not a substitute. B12 deficiency causes neurological damage that may be irreversible.

More benefits

• High-quality complete protein. 20.3 grams per 100 grams, with all nine essential amino acids. The PDCAAS score of soy protein is about 0.9-1.0 — on par with egg and milk.

• The highest protein density among whole soy products — more than tofu, edamame and soy milk.

• Dietary fiber — about 6 grams per 100 grams. An advantage almost absent from tofu. It contributes to satiety, the microbiome and blood sugar regulation.

• Manganese — 57% of the daily value in 100 grams, and phosphorus — 38%.

• Riboflavin (B2): fermentation raises its content — about 0.36 mg per 100 grams, three times as much as tofu.

• Minimally processed. Good tempeh contains two ingredients: soybeans and a culture. Unlike industrial “meat substitutes” with a long ingredient list.

• Almost no sodium in the basic product — 9 mg per 100 grams.

• Soy and hormones: as with tofu — meta-analyses of controlled trials found no effect on testosterone or estrogen in men at dietary amounts. Isoflavones bind mainly to the estrogen receptor beta, with a potency orders of magnitude lower than human estrogen.

Downsides and considerations

• A bitter taste — the main practical downside. Tempeh has a characteristic bitterness, a byproduct of fermentation. It is the number-one reason people try it once and never come back. The fix is simple and effective: steam or gently simmer it for 10 minutes before cooking. This removes most of the bitterness and opens up the texture to absorb a marinade. It is the single step that makes the biggest difference, and it is almost always left out of recipes.

• Soy allergy: one of the leading allergens in children, and it requires complete avoidance.

• Relatively low calcium compared with tofu: 111 mg per 100 grams, versus 200-350 mg in tofu coagulated with calcium sulfate. If you rely on soy products as a calcium source, tofu is the better choice.

• Purines: a medium-to-high content. Relevant for people with gout.

• Thyroid and medications: soy may interfere with the absorption of thyroxine. Leave at least 4 hours between taking the medication and eating soy products. With normal thyroid function and adequate iodine intake there is no effect.

• Higher calorie density than tofu: 192 vs. 144 calories per 100 grams. Still entirely reasonable for the protein it provides.

• Flavored and ready-made tempeh products: “flavored,” smoked or pre-fried versions usually contain significant amounts of sodium, oils and sugar — a different product from basic tempeh.

• Availability and price in Israel: less common than tofu and usually more expensive.

How to tell if tempeh is good

This question comes up almost every time someone buys it for the first time:

The black spots are the most common point of confusion — they are completely normal and are not harmful mold.

Practical use

• Steam or simmer for 10 minutes before anything else. It removes bitterness and opens it up to absorb a marinade. The most important step.
• A generous marinade — coconut aminos or soy sauce, garlic, ginger, maple syrup and apple cider vinegar. At least 30 minutes after steaming.
• Slice thin or crumble — thin fried slices are reminiscent of bacon; crumbled tempeh is excellent in tomato sauce, tacos or Bolognese.
• Fry until crunchy — tempeh absorbs less oil than tofu and browns nicely.
• A typical serving: 100 grams — 20 grams of protein and 6 grams of fiber for 192 calories.
• Pair it with vitamin C — lemon, red pepper or tomato — to improve absorption of non-heme iron.
• Take a B12 supplement separately — tempeh is not a source, period.
• Storage: in the fridge until the expiration date; in the freezer for up to several months. Freezing does not harm the texture.

Summary

Tempeh is the most whole and nutrient-dense soy product: 20.3 grams of protein per 100 grams — more than tofu — along with about 6 grams of fiber that is almost absent from tofu, because the bean stays whole rather than being filtered. Fermentation adds a real, measurable advantage: the mold secretes phytase, which breaks down phytic acid, so the iron, zinc and magnesium are more available to the body than in unfermented soy.

Two practical points are worth more than everything else: steam it for 10 minutes before cooking — this removes the bitterness that makes most people give up on it after one try — and do not rely on it as a source of B12. The mold does not produce B12; what was measured in the past came from random bacterial contamination, and hygienically made commercial tempeh contains negligible amounts. Vegans need a supplement or fortified food, without exception.