Tofu

Tofu

Tofu (in Hebrew “טופו”) is made from just three ingredients: soybeans, water and a coagulant. It is produced in a process reminiscent of cheese making: soybeans are soaked and ground into a drink, which is curdled with a coagulant, and the curds are pressed into molds. It originated in China about two thousand years ago, and it is a major source of protein in East Asian cuisines.

100 grams of firm tofu provide about 144 calories, 15-17 grams of protein, 8 grams of fat and 2-3 grams of carbohydrates. Silken tofu contains less protein (about 5-8 grams) and more water.

The coagulant determines the calcium content

This is the most important practical point about tofu, and it is almost always missing from the discussion.

There are two main coagulants:

• Calcium sulfate (gypsum) — used in most Western industrial tofu. It adds a large amount of calcium — 200-350 mg per 100 grams, an amount comparable to cheese and even higher than milk by weight.
• Nigari (magnesium chloride) — used in traditional Japanese tofu. It gives a more delicate texture and flavor, but contributes almost no calcium — usually less than 50 mg per 100 grams.

The difference is five- to sevenfold. Tofu is not automatically a “calcium source” — it depends entirely on the ingredient list. If you rely on tofu as a calcium source on a vegan diet, you must check that calcium sulfate is listed.

Another advantage: the calcium in tofu is well absorbed — about 30%, a rate similar to milk — because the oxalate content of soy is low, unlike spinach.

Health benefits

• High-quality complete protein: soy protein is one of the few plant proteins that supplies all nine essential amino acids in sufficient amounts. Its PDCAAS score reaches about 0.9-1.0 — on par with egg and milk protein, and significantly higher than most plant protein sources. For vegetarians and vegans it is one of the most important sources.

• Protein for building muscle: trials comparing soy protein with whey protein found that both support muscle building, although milk protein has a slight edge because of its higher leucine content. The gap closes almost completely when total protein intake is sufficient.

• Fat profile: most of the fat in tofu is unsaturated, and it is cholesterol-free. The FDA has approved a health claim that 25 grams of soy protein a day, in a diet low in saturated fat, may reduce the risk of heart disease.

• Isoflavones: as described under soy milk — phytoestrogens that bind mainly to the estrogen receptor beta, with a potency thousands of times lower than human estrogen. Meta-analyses of controlled trials found no effect on testosterone or estrogen in men at dietary amounts. Regarding breast cancer, cohort studies lean toward a protective or neutral effect, and leading organizations do not recommend avoiding it.

• Iron and minerals: a good source of iron (though it is non-heme and less well absorbed — pairing it with vitamin C improves absorption), manganese, phosphorus and selenium.

• Moderate calorie density: 144 calories per 100 grams with 15-17 grams of protein — a very good protein-to-calorie ratio, suitable for weight management.

• Minimally processed food: unlike industrial “meat substitutes,” traditional tofu contains just three ingredients: soy, water and a coagulant.

Downsides and considerations

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

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

• Phytate: reduces the absorption of iron and zinc. The production process removes some of it, and including vitamin C in the meal offsets it.

• Neutral texture and flavor: tofu on its own is almost tasteless — a culinary advantage (it absorbs flavors) that is often experienced as a downside. Most failures with tofu come from poor preparation, not from the product.

• Processed tofu products: tofu sausages, schnitzels and “flavored” products usually contain significant amounts of sodium, oils and additives. These are entirely different products from plain tofu.

• Unpredictable calcium content: as described above — it depends entirely on the coagulant.

Types of tofu

Practical preparation — what changes the result

Pressing: firm tofu holds a lot of water. Pressing it — between two plates with a weight on top for 20-30 minutes, or in a tofu press — concentrates the protein, improves the texture, and allows much better marinade absorption. It is the single step that makes the biggest difference.

Freezing and thawing: a lesser-known and very effective trick. Freezing creates ice crystals that tear the tofu’s structure; after thawing you get a much spongier, chewier texture that soaks up marinade beautifully and is reminiscent of a meaty texture.

Starch for crispness: coating pressed cubes with a tablespoon of cornstarch before frying or baking creates a crisp crust.

Marinade: because it is so neutral, tofu needs aggressive seasoning. Coconut aminos or soy sauce, garlic, ginger and sesame oil are a classic base. Give it at least 30 minutes.

Silken tofu is not interchangeable with firm — it is meant for smooth textures, not for roasting.

Summary

Tofu is one of the best plant protein sources there is — complete protein of a quality comparable to egg and milk, at a reasonable calorie density and with minimal processing. Concerns about isoflavones are not supported by the evidence. Two practical points to take away: check the coagulant in the ingredient list if calcium matters to you, and press or freeze it before cooking — that is where the difference between good and failed tofu lies.