Soybeans have long been used as human food in Asia in such traditional foods as tofu, soymilk, tempeh and natto. Some of these foods have become popular in other parts of the world.
In recent years, however, breakthroughs in food science and processing have made it possible to use soybean ingredients in new ways, creating foods that are familiar to consumers but that incorporate parts of the soybean for functional or nutritional purposes. This has greatly expanded the food processing industry’s use of soybeans and soy-based ingredients.
Tofu is perhaps the most widely consumed soyfood in the world. It is a regular part of the diet in many Asian nations and is available across the United States and in most Western nations. This soft, white, almost cheese-like food is favored for its versatility, mild flavor and high nutritional value. Since it is naturally processed it retains a good deal of the soybean’s important nutrients and phytochemicals, such as the isoflavones.When tofu is made, whole soaked soybeans are ground to produce a slurry, which is added to water and boiled. After cooking, the pulp is removed from the mixture, and what is left is soymilk. While the soymilk is still hot, a natural mineral coagulant, such as calcium sulfate, magnesium chloride, or a mixture of both, is added slowly to the hot liquid. Within minutes, the soymilk begins to curdle and large white clouds of tofu curd begin to form in a sea of yellow whey. After 15 minutes or so, the curds are removed from the whey and placed in cloth-lined forming boxes where pressure is applied to the top. The curds are then pressed to form soft, regular, firm or extra firm tofu. The size of the curd and length of pressing time determines the style of tofu made. The softer the tofu, the lower the protein and fat level and higher the water content. Soft tofu is also usually smoother in texture than firm tofu. Firm tofu, on the other hand is higher in protein and fat, lower in moisture and will have a denser, chewier texture. Silken tofu, the soft variety sold in either an aseptic box package or the usual tofu tub, is made in a slightly different manner: either calcium sulfate or glucono-delta-lactone is added to a thick, rich soymilk, and the mixture is put into a package. This package, with the soymilk and coagulant mixture, is heated to the proper temperature to activate the coagulation and the soymilk is transformed into one solid, smooth curd, right in the package. Typically, tofu contains between 10 and 15 percent protein and 5 to 9 percent fat. It is relatively low in carbohydrates and in fiber (as the pulp was removed), making it easy to digest.
Traditionally, soymilk is the liquid extract of the soybean that can be used in the preparation of tofu, or as a nutritious beverage. But beverage-quality soymilks available today are usually prepared in a slightly different fashion, utilizing more modern food processing techniques in order to produce a blander product with greater taste appeal. As with tofu, soymilk contains most of the active phytochemicals present in soybeans, including high amounts of isoflavones. There are also a number of soymilks available that are fortified with vitamins and minerals, such as beta-carotene and calcium or docosahexaenoic acid (DHA), an omega-3 fatty acid.The popularity of soymilk has grown quickly in the U.S. and Europe since the 1980s. As refrigerated soymilks came onto the market in the late 1990s (beginning with WhiteWave's Silk), the industry rocketed from $156 million in U.S. sales in 1997 to well over $800 million in 2005. Over 80 percent of the market is owned by the refrigerated soymilk category.
Green Vegetable Soybeans (Edamame, Mukimame)
This simple and nutritious soyfood is really just the whole soybean picked at its peak of green maturity, at a time when it is high in sucrose and chlorophyll, and has a firm texture. It is harvested in the pod, and sold either in the pod or shucked, after being blanched and frozen. Because they are picked when their sugar levels are high, green vegetable soybeans are very sweet.The common and traditional names for “green vegetable soybeans” are “edamame” (when sold in the pod) and “mukimame” (when sold as individual beans).Green vegetable soybeans contain about thirteen percent protein, the same amount as tofu, and are naturally high in calcium. They work very well in stir-fry dishes, and can also be blended into dips and other preparations.
Tempeh is a traditional fermented soyfood from Indonesia and is quite unique in its texture, flavor and versatility. Tempeh has a distinctive flavor that is sometimes described as “nutty” or “mushroom-like.”It is made from the whole soybean, which has been dehulled, cracked and cooked in water with added vinegar to reduce the pH. Once cooked, the soybeans are mixed with the spores of the Rhizopus oligosporus fungus and left to incubate for 24 hours at around 88°F. At the end of this period, the tempeh is a compact, cake-like product, completely covered with, and penetrated by, the white mold mycelia that has formed. Various grains or seeds may be mixed in during processing to vary the taste and texture of the final product.Tempeh contains about nineteen percent protein, is higher in fiber than tofu, and is a significant source of vitamins and minerals.
Miso is a rich and flavorful paste made from fermented and aged whole soybeans, or from soybeans in combination with wheat, barley or rice. This salty paste is a treasured soup-base and flavoring ingredient used throughout Japan, Korea, Taiwan, Indonesia and China. There are many types of miso available, from sweet white miso, which is quite mild, to dark savory miso, which is much more robust and salty. Miso has some unique medicinal properties and is believed to help reduce the effects of environmental poisons on the body, and contains enzymes and bacteria that can aid in digestion. It is high in protein, but also contains a large amount of sodium and should be consumed sparingly.To make miso, whole cooked soybeans are mixed together with koji nuggets — grain such as wheat, rice or barley which has been cultured with a fungal starter,Aspergillus oryzae — and fermented under very specific conditions for the type of miso being made. When the mash is fully ripened, it is blended and packaged for sale.
Soy sauce is the most well known and popular of the traditional soyfoods, used extensively as a flavoring ingredient in most Asian cooking.When naturally processed, soy sauce is produced in a manner similar to that of miso. When made exclusively with soybeans, the product is called “tamari.” When it is processed with a fermented wheat starter, the product is called “shoyu.” Much of the soy sauce sold today is made with hydrolyzed vegetable protein, or HVP, with added sugar, color and preservatives. HVP is produced from soy protein using a chemically-induced fermentation. All soy sauces are high in sodium and should be used sparingly. There are some reduced sodium varieties on the market today, as well as a number of flavored soy sauce products.From a nutritional prospective, tamari contains the highest protein level of the soy sauces, followed by shoyu and then the HVP-based soy sauce. But the high amount of sodium in all of these products should preclude anyone from using soy sauce as a nutritional food.
Natto is a whole soybean food (very popular in Japan) that is produced by fermenting small, cooked soybeans with Bacillus natto until they develop a sticky, viscous coating. It has a strong taste and aroma and is definitely for the adventurous eater. It can be found frozen, or fresh, and will last about a week refrigerated.
Okara is the fibrous remains of the soybean after it has been processed to make soymilk. It is very high in moisture content and contains the insoluble carbohydrates and dietary fiber of the soybean, as well some remaining protein and fat. If fully cooked, it is bland in flavor and is an excellent ingredient to add to breads and other baked goods. It can also be used to make meat alternatives and can be processed into tempeh. It is not usually sold in stores, as it is very wet, heavy and highly perishable.
Soy sprouts are the fresh, crisp sprouts of germinated soybeans sold after having grown for 5 to 7 days. They are a traditional food of Korea and eaten either raw or in prepared food dishes. They are high in protein and fiber, and contain vitamin C. Soy sprouts are slightly larger than ordinary bean sprouts that are prepared from mung bean seeds.
Soybean oil is produced from soybeans by mechanical or solvent extraction. Crude soybean oil is further filtered or refined to produce salad and cooking oils. In the U.S., most of what is sold as “vegetable oil” in the stores is really pure soybean oil. In other countries, it is often labeled as soybean oil, or soya oil. It is the primary oil used in the food processing industry and is found in vegetable oil shortenings and margarine.Soybean oil is high in polyunsaturated fats, low in saturated fats, and a good source of linoleic and linolenic acids, the Omega-3 and Omega-6 fatty acids also found in fish oils.
Second Generation Soyfoods
Soyfoods manufacturers have been very responsive to consumer demands for convenient, healthful foods. As a result, a wide array of “second generation” soyfoods is available in the marketplace today, catering to different tastes and use preferences. One can now find tofu-stuffed pasta products, as well as tofu-based dips, dressings and puddings. Soymilk is made into yogurt, ice cream and cheese. Tempeh and tofu are now available flavored, marinated, baked or smoked. Pizza is topped with soy cheese alternatives, and textured soy concentrate is mixed with gluten to form a ground meat alternative. Here are some less traditional soyfoods that are currently available:
Soynuts are crunchy nuts that have been prepared by the dry roasting or oil roasting of whole or split soybeans that have first been soaked in water. They can be sold with salt or other flavoring ingredients added as a coating. Soynut pieces can be blended with other nuts and used in baking applications and other food preparations. Soynuts are high in protein, fiber and the isoflavones found naturally in whole soybeans.Soynut butter is a paste of ground soynuts that have been prepared in a similar manner to peanut butter, and may have salt, sweeteners and additional oil added.
This is product category contains hundreds of products made from tofu, tempeh, textured soy flour, textured soy concentrate, isolated soy protein and wheat gluten. Products may take the shape of burgers, hot dogs, sausages, luncheon meats, ground meat and meatballs. Most products are made with a combination of vegetable protein ingredients to achieve the best texture and are flavored for a particular use. Most are low in fat and many are completely fat free.
Block, sliced, spreadable and grated cheese alternatives may be made from soymilk, tofu or other vegetable protein ingredients. They can be found flavored like American cheese, mozzarella, cheddar, Monterey jack, Parmesan and others. Most of these products are made with some amount of casein (from cow’s milk) because this protein responsible for the melting action in cheese when heated. Without casein, soy cheese alternatives soften, but do not melt or stretch. They also add a flavor note that is associated with cheese products. Some products are available without casein. Soy-based cheese alternatives have either had their fat replaced with vegetable oil or completely removed.
Soymilk yogurt is made in the same manner as cow’s milk yogurt. Pasteurized soymilk is inoculated with Acidophilus, Bifidos or other suitable cultures and incubated until the culture has turned the soymilk into yogurt. It tastes very similar to cow’s milk yogurt and is available in a variety of styles and flavors. It is very high in protein, a great source of isoflavones and can be used as is or in recipes calling for yogurt. These products may not legally be labeled as “yogurt” in the U.S. since they are not made with cow’s milk. Generally packaged in a familiar yogurt container, they may sport names such as “soygurt” or “cultured soymilk.”
Nondairy Frozen Desserts
Nondairy frozen desserts are produced in much the same manner as their dairy counterparts. They may be prepared from a base of soymilk, soymilk yogurt, tofu or isolated soy protein. Some brands, such as the pioneering Tofutti brand, have created a loyal niche for themselves, but the category as a whole still struggles to reach a broad market.
European Natural Soyfoods Association: Vegetable Protein Association: Soy Products Manufacturers Association (SOJAXA): African Soyfood Association: Association of North America: Soyfoods Council: