Tofu is a highly versatile and nutritious food made from soybean curd. Although the word “tofu” is Japanese, the food seems to have originated in ancient China, where the Mandarin word is “dofu”.
The creation of tofu is generally attributed to Liu An, the ruler of Huai-Nan during the 2nd century BCE. The creation of tofu was probably accidental. Although soybeans are not technically a grain, the Chinese considered soybeans as one of their essential five sacred grains, along with rice, wheat, barley, and millet.
It is likely that Liu An prepared soybeans by drying, mashing, and boiling them like grains. Adding sea salt will not only season the puree, it will also act as a solidifying agent for curdling. Another theory suggests that the curd-making process was imported only from neighboring regions. Regardless, soybeans appear to have been processed into tofu as far back as the 2nd century BCE using sea water precipitates to solidify the tofu, a process still used by many manufacturers.
According to ancient text, soybeans were cultivated in northern China during the Chang period at least in the 15th century BC. A sixth-century Chinese encyclopedia, the first of its kind, states that the explorer Chocán brought soybeans back to China from his expeditions to Greece, Rome, and India. However, according to legend, the soy plant was cultivated centuries earlier. In 2838 BCE, Emperor Sheng-nung wrote a treatise on plants that described the soy plant in detail.
In 2207 BC, Chinese agricultural expert also wrote about soybean cultivation. Clearly, soybeans were an important staple crop in China for a long time. Soybean was also recognized for its regenerative properties: soybean roots have nodules, which discharge nitrogen, and thus enrich the soil. This important quality left its mark on the old school of thought for the soy plant “su”, which had short lines to symbolize the roots.
During the eighth century, Chinese Buddhist missionaries introduced the soy plant to Japan and Korea, although they may have been used there much earlier. Buddhist monks believed that a vegetarian diet was healthier for the soul, so they advocated eating protein-rich tofu as a substitute for meat. The upper classes of Japan first adopted tofu in their diet and by 1400, during the Muromachi period, tofu was popular among all classes in Japan.
Until World War II most Japanese and Chinese tofu was made in small family-run shops, each of them using similar ingredients, methods, and equipment. In the 1960s, the Japanese Food Research Institute made recommendations for the modernization and standardization of tofu production throughout the country. His suggestions included the use of calcium sulfate as a thickening agent instead of the natural seawater precipitate, nigari.
He also recommends using a pressure cooker to speed up the process. Hydraulic presses and centrifuges replaced manual lever presses and hand-held screw presses. High-speed grinders and aluminum boxes replaced the original wooden boxes. Despite improvements in efficiency and productivity, many believed that the new methods compromised the taste of tofu. Traditionalist producers still retain the old-fashioned tofu production.
In America, Americans did not readily adopt soybeans in their diet. They were available as far back as the mid-1700s and were popularized by Chinese immigrants traveling to California during the Gold Rush in the mid-1800s. As Chinese immigrants later traveled to other parts of the country, they spread the recipe for tofu.
The demand for tofu and other Asian foods also increased after World War II as military personnel returned from Asia, with some Asian spouses. Until the 1900s soybeans were grown as a cash crop – primarily to regenerate soils during crop rotation – as animal feed, and for the production of oil and oilseed residues for manufacturing purposes. By the 1950s, the US competed with Asia in soybean production. Forty years later, the U.S.
During the 1970s, with the increasing popularity of ethnic foods in America, mainstream grocers began offering products such as tofu. At the same time, the price of meat soared, and tofu eventually caught on as a popular substitute for meat, as tofu is high in protein and low in saturated fat. The growing health-awareness of the American population also contributed to the popularity of tofu. Twenty years later the tofu industry grew to over £4 million.
Soybeans are perfectly balanced in the major food categories of proteins, fats, and carbohydrates, as well as vitamins, and minerals. Soybeans also contain an ideal amount and combination of amino acids which are essential for the assimilation of nutrients by the human body.
The scientific name of soybean is Glycine max, and it is part of the botanical family Leguminaceae. The soy plant has a slightly woody stalk and reaches a height of 30–36 inches (76–91 cm). The whole plant is covered with green hairs. The leaves grow in clusters of three and fall off as the beans mature. The soy plant produces papilionaceous (butterfly-shaped) flowers.
Which are either white, red or purple in color. The pods grow to 1–2 inches (2.5–5 cm) in length, each containing two or three seeds, which become soybeans. Soy seeds are either round or oval and are similar in size to a pea. Their color is usually yellow but they can also be green, purple, brown or a mixture of colours. Soybeans are pulses, that is, the plant has a symbiotic relationship with bacteria, called rhizobia,
The soy plant can grow north up to 52 degrees latitude, even though it is actually a subtropical plant. Growing soybeans requires slight variations in each climate, but in general, the beans are sown with heavy machinery in mid-May. As the beans ripen, the soy leaves fall off. After a short growth period of 15 weeks, only the stalk and pod remain. Plants are harvested mechanically.
The ingredients for making tofu are less. These include soybean milk, water and coagulation agents. The modern tofu manufacturing process is largely an automated version of the traditional method, and most of the modern equipment is made in Japan. While an individual tofu maker may operate with 20 gallons (761) of beans at a time, a contemporary processing facility can produce about 3.5 tons of tofu per day using 5.7 tons of soybeans.
The first step in making tofu is soaking and milking the soybeans. A coagulant is added to keep the milk from curdling. A traditionally used coagulant is nigari, a seawater precipitate rich in minerals such as magnesium and calcium chloride. But modern manufacturers use either calcium sulfate or magnesium chloride. The soy curd is then processed into tofu in the desired form, mainly in custard-like blocks. A variety of textures can be produced depending on the amount of water. Tofu comes in soft, firm and extra-fime as well as silky or liquid form. Many tofu flavors are also available, such as jalapeno and cheddar.
- Dried beans, which come in 60 lb (27 kg) sacks, are soaked in water for 12 to 14 hours. The beans become soft as they absorb water and double in size.
- After soaking, the beans are mashed with special Japanese stone grinders or other pureing machines and mixed with water into a slurry. The solution is boiled to neutralize the enzymes that hinder digestion.
- Soymilk is extracted with a roller press, separating it from the pulp, which consists of the hull and fiber. This process may take about two hours to complete. The leftover pulp can be used to feed livestock.
soy milk freeze
4 Once the whey is extracted, soybean juice is poured into the curd vats. A coagulation agent is added, such as calcium sulfate, magnesium chloride, or nigari. The coagulant alters the pH and makes the milk similar to the curdling process. This step takes about 20 minutes.
5 Traditionally, curd is pressed with a hand held screw press or a simple lever press. Tofu can be pressed into cheesecloth-lined boxes. Modern systems use centrifuges or hydraulic presses. The whey drains out, leaving soft blocks of pressed curds. Tofu can be made in a variety of textures, from a dense cheese-like texture to a soft or liquid form.
6 automated cutters cut cake tofu into 1-pound (.45 kg) blocks. Tofu blocks are washed in vats of water where they harden and are stored until they are ready to be processed further.
packaging of tofu
7 Tofu can be packed in shrink-wrapped blocks or continuous thermo-form packages. Water can be added to packages, or tubs, and then they are sealed, weighed and dated. Some companies process soy milk directly into its package.
8 Packaged tofu is pasteurized at approximately 180°F (82°C). Pasteurization extends the shelf life of tofu to about 30 days. The tofu is then cooled in water until it is ready to be placed in boxes and shipped to distributors. To keep tofu fresh, it must be refrigerated below 45°F (7°C).
Technology will continue to improve the taste and texture of tofu. Dozens of new tofu products enter the market each year, and that segment has expanded to over $100 million in the 1990s. The demand for soy-based food products is most likely to increase as medical research uncovers health benefits associated with soybean consumption, namely the prevention and treatment of heart disease and cancer.
Where else to learn
Toussaint-Samat, Maguellon. A History of Food, translated from French by Anthea Bell, Blackwell Reference, 1987 in French, 1992 translation.
Clifford, Carlson. “Utilitarian soybean curd turns exotic.” San Francisco Business Times, June 28, 1991, p. 1.
“Soy: Bean Most Likely to Succeed in Preventing Cancer, Heart Disease.” Environmental Nutrition, May 1994, p.1.
Gerriots, Marcy, Linda Cooke, and Marcia Wood. “Soy! This Is No Ordinary Bean: Part 2.” Agricultural Research, November 1993, p. 10.
Hewitt, Linda. “An attractive alternative: protein from fungus and soy.” Food Manufacturing, May 1994, p. 25.
Kevin, Kitty. “Tofu Comes Off Age.” Food Processing, June 1994, pp. 81-82.
“Tofu Spreads as a Healthy Choice in the American Diet.” Supermarket Business Magazine, February 1992, p. 16a.
Wagner, Bill. “A surprising source for new foods.” FDA Consumer, November 1993, p. 28.