Tofu

Tofu is a food prepared by coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness: silken, soft, firm, extra firm. (Bean curds).

Tofu is a traditional food product made primarily from soybeans, produced by coagulating soy milk, which is derived from soaked, ground, and boiled soybeans.

The coagulation process typically involves the addition of coagulants such as calcium sulfate or magnesium chloride, which cause the soy proteins and lipids to form a curd.

This curd is then pressed into solid blocks to form tofu.

Tofu is translated as bean curd.

Tofu is a traditional component of many East Asian and Southeast Asian cuisines; in modern Western cooking, it is often used as a meat substitute.

Nutritionally, tofu is low in calories, while containing a relatively large amount of protein.

It is high and reliable source of iron, and can have a high calcium or magnesium content depending on the coagulants (calcium chloride, calcium sulphate, magnesium sulphate) used in manufacturing.

Cultivation of tofu, as a protein-rich food source, has one of the lowest needs for land use (1.3 m²/ 1000 kcal).

Tofu emits some of the lowest amount of greenhouse gas emissions (1.6 kg CO2/ 100 g protein).

The production of tofu essentially consists of:

The coagulation of the soy milk to form curds.

The pressing of the soybean curds to form tofu cakes.

It is similar to the production of dairy cheese by coagulating the milk of dairy animals to form curds and pressing and aging the curds to form cheese.

It is known for its high-quality plant protein content and is a staple in many vegetarian and vegan diets due to its nutritional benefits.

The texture and quality of tofu can vary significantly based on the processing parameters, including the type of coagulant used, the solid content of the soy milk, and the pressing conditions.

Typical tofu-making procedures are cleaning, soaking, grinding beans in water, filtering, boiling, coagulation, and pressing.

Japanese raw silken tofu the curds are not pressed.

Coagulation of the protein and emulsion suspended in boiled soy milk is the most important step in the production of tofu.

There are many variations including the variety and percentage of protein in the soybeans used, slurry cooking temperature, and coagulation temperature.

Soybean proteins are mainly composed of 7S and 11S proteins.

The negative surface charges on these globulins usually cause them to repel each other.

Heating soy milk denatures the proteins and exposes hydrophobic groups.

As the net charges of the protein molecules are neutralized, attractive hydrophobic interactions dominate over repulsive electrostatic charges: as a result protein aggregates are formed.

The coagulant itself is tasteless.

Gypsum, calcium sulfate, is quarried from geological deposits, and no chemical processing or refining is needed, making it the cheapest coagulant used in tofu production.

Use of this coagulant also makes tofu that is rich in calcium.

Other coagulants include nigiri which consists primarily of magnesium chloride, is produced from seawater after the sodium chloride is removed and the water evaporated.

Fresh clean seawater itself can also be used as a coagulant.

Acid coagulants: Glucono delta-lactone (GDL): A naturally occurring organic acid also used in cheesemaking, this coagulant produces a very fine textured tofu that is almost jelly-like. It is used especially for “silken” and softer tofus and confers a faint sour taste to the finished product.

This acid coagulant is also commonly used together with calcium sulfate to give soft tofu a smooth, tender texture.

Other edible acids can affect the taste of the tofu more, and vary in density and texture, acids such as acetic acid (vinegar) and citric acid (such as lemon juice), can also be used to coagulate soy milk and produce tofu.

Among enzymes that have been shown to produce tofu are papain, and alkaline and neutral proteases from microorganisms.

One or more coagulants produce the desired texture in the finished tofu.

The coagulant mixture is dissolved in water, and the solution is then stirred into boiled soy milk until the mixture curdles into a soft gel.

Coagulants are typically added at concentrations between 1.5 and 5.0 g/kg.

In all coagulants consisting of calcium or magnesium salts, the positive double-bonded ions of the calcium or magnesium are responsible for the coagulation of the soy proteins which become part of the tof enhancing its nutritional value.

Only 1 part per 1000 of the tofu eaten is coagulant.

Most of the coagulant reacts with soy protein and is broken down into ions.

The finished tofu can then be cut into pieces, flavored or further processed.

The whiteness of tofu is ultimately determined by the soybean variety, soybean protein composition, and degree of aggregation of the tofu gel network.

The yellowish-beige color of soybeans is due to the color compounds including anthocyanin, isoflavones, and polyphenol compounds; therefore the soybean variety used will predicate the color of the final tofu product.

Tofu flavor is generally described as bland.

Tofu products can be split into two main categories: fresh tofu which is produced directly from soy milk, and processed tofu, which is produced from fresh tofu.

Tofu can be categorized into different types based on its texture, such as silken, soft, firm, and extra-firm tofu, each suitable for differing culinary applications.

The nutritional profile of tofu includes essential amino acids, making it a complete protein source, and it is also rich in iron, calcium, and other micronutrients.

Unpressed fresh tofu is gelled soy milk with curd that has not been cut and pressed of its liquid.

Unpressed tofu is so soft that it is directly ladled out for serving or sold with its gelling container.

Overall, tofu is a versatile and nutritious food.

Generally, the firmer styles of tofu are used for kebabs, mock meats, and dishes requiring a consistency that holds together, while the softer styles can be used for desserts, soups, shakes, and sauces.

Some people enjoy tofu made and prepared with chocolate and making it into pies and mousse along with other tofu desserts.

This came about due to vegans and vegetarians avoiding the usage of items such as milk and eggs.

Western tofu types can be barbecued since they hold together on a barbecue grill.

Silken tofu may be used to replace cheese in certain dishes.

Tofu and soy protein can be industrially processed to match the textures and flavors of cheese, pudding, eggs, bacon, and similar products.

Tofu’s texture can also be altered by freezing, puréeing, and cooking.

Tofu (Nutritional value per 100 g (3.5 oz)

Energy 317 kJ (76 kcal) Carbohydrates 1.9 g Fat 4.8 g Protein 8 g Vitamins and minerals Other constituents Quantity Water 85 g

Raw regular tofu is 85% water, 8% protein, 2% carbohydrates, and 5% fat.

100 g (3.5 oz), tofu supplies 76 calories, and is a rich source (20% or more of the Daily Value) of calcium, copper, iron, and manganese.

The two main components of the soybean important in tofu contain glycinin, and hemagglutinins, lipoxygenases, b-amylase, and β-conglycinin.