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Facts on Soy Protein

Soy protein is generally regarded as the storage protein held in discrete particles called protein bodies which are estimated to contain at least 60-70% of the total soybean protein. Upon germination of the soybean, the protein will be digested and the released amino acids will be transported to locations of seedling growth. Legume proteins, such as soy, and pulses belong to the globulin family of seed storage proteins called leguminins (11S) and vicilins (7S), or {the trivial names glycinin and beta-conglycinin in soybeans}. Grains contain a third type of storage protein called gluten or "prolamines". Soybeans also contain biologically active or metabolic proteins such as enzymes, trypsin inhibitors, hemagglutinins, and cysteine proteases. The soy cotyledon storage proteins, important for human nutrition, can be extracted most efficiently by water, water plus dilute alkali (pH 7-9), or aqueous solutions of sodium chloride (0.5-2 M) from dehulled and defatted soybeans that have undergone only a minimal heat treatment so that the protein is close to being native or undenatured. Soybeans are processed into three kinds of protein-rich products; soy flour, soy concentrate, and soy isolate.

Soy protein {90%protein (N x 6.25) on a moisture-free basis} has been available since 1935 for its functional properties. In 1935, African-American chemist, Percy Julian, designed and supervised construction, at the Soy Products Division, Glidden Paint Company, Chicago, Illinois, of the world's first plant for the "isolation" of industrial-grade soy protein. The largest use of industrial grade protein was and still is for paper coatings, in which it serves as a pigment binder. However, Dr. Julian's plant must have also been the source, of the "soy protein isolate" which Ford's Robert Boyer and Frank Calvert spun into an artificial silk that was then tailored into that now famous, "silk is soy" suit which Henry Ford wore on special occasions. The plant's eventual daily output of forty tons of soy protein isolate made the Soya Products Division, Glidden's most profitable division.

During WWII, the fire extinguishing, soy protein foam, "Aero-Foam", the U.S. Navy's fire-fighting "bean soup", was the brainchild of Percy Lavon Julian. The soy protein foam could smother oil and gasoline fires on board ships, especially aircraft carriers, before the flames could engulf and perhaps sink the ship. It saved the lives of countless thousands of American sailors. The foam was a hydrolyzate of isolated soy protein.

In 1958, Central Soya of Fort Wayne, Indiana acquired Dr. Julian's, Soy Products Division (Chemurgy) of the Glidden Paint Company, Chicago. Recently, Central Soya's (Bungee) Protein Division, in January,2003, joined/merged with DuPont's soy protein (Solae) business, which in 1997 had acquired Ralston Purina's soy division, Protein Technologies International (PTI), St. Louis, Missouri. Eighth Continent, an "ersatz" soy milk is a combined "venture" product of DuPont's Solae, protein isolate and General Mills with a production facility in Minneapolis, MN.

Food grade, soy protein isolate, first became available on October 2, 1959 with the dedication of Central Soya's edible soy isolate, Promine D, production facility on the Glidden Company industrial site in Chicago. An edible soy isolate; and edible spun soy fiber has also been available, since 1960, from Ralston Purina Company of St. Louis, Ill. who had hired Boyer and Calvert. In 1987, PTI became the world's leading maker of isolated soy protein.

Recently, soy protein popularity has increased due to its use in health food products.

Food uses
Soy protein is used in a variety of foods such as salad dressings, soups, vegetarian foods, meat imitations, beverage powders, cheeses, coffee whiteners, frozen desserts, whipped toppings, infant formulas, bread and rolls, cereals, pasta products, oriental foods and pet foods.

Functional uses
Soy protein is used for emulsification and texturizing. Specific applications include adhesives, asphalts, resins, cleaning materials, cosmetics, inks, leather substitutes, paints, paper coatings, pesticides/fungicides, plastics, polyesters and textile fibers.

Production methods
Edible soy protein "isolate" is derived from defatted soy flour with a high solubility in water (high NSI). The aqueous extraction is carried out at a pH below 9. The extract is clarified to remove the insoluble material and the "supernatant" is acidified to a pH range of 4-5. The precipitated protein-curd is collected and separated from the whey by centrifugation. The curd is usually neutralized with alkali to form the sodium proteinate salt before drying.

Soy protein concentrate is produced by immobilizing the soy globulin proteins while allowing the soluble carbohydrates, soy whey proteins, and salts to be leached from the defatted flakes or flour. The protein is retained by one of several treatments: leaching with 20-80% aqueous alcohol/solvent; leaching with aqueous acids in the isoelectric zone of minimum protein solubility, pH 4-5; leaching with chilled water in the presence or absence of calcium or magnesium cations; leaching with hot water of heat-treated or toasted defatted soy meal/flour.

All of these processes result in a product that is 70% protein, 20% carbohydrates (2.7 to 5% crude fiber), 6% ash and about 1% oil, but the solubility may differ. One ton of defatted soybean flakes will yield about 750 kg of soybean protein concentrate.

Product type: Isolates
Soy protein isolate is the most refined form of soy protein and also has the highest soy protein content (90%). It is made from defatted soy meal which has had most of the fats and carbohydrates removed. Because of this, it has a neutral flavor and will cause less gas due to bacterial flatulence.

Soy isolates are mainly used to improve the texture and eating quality of meat products, but it is also used for other nutritional (increasing protein content), sensorial (better mouth feel, bland flavor) and functional reasons (for applications requiring emulsification, water and fat absorption and adhesive properties). Specifically, it is used in the following food products; breakfast cereals, energy and protein bars, weight loss ready-to-drink beverages, soups, sauces, baked foods, ice cream, yogurt and other dairy or dairy-free products, meat alternatives and processed meat, poultry and fish products.
Soy protein isolate is used as a health food as it is a complete vegetable protein containing all the essential amino acids for growth. Also, it has a very low fat content when compared to animal sources of protein, such as meat or milk. It is also claimed that soy protein isolate may reduce the risk of coronary heart disease and help prevent osteoporosis, some cancers and menopausal symptoms.

Pure soy protein isolate is used mainly by the food industry and is difficult for the consumer to obtain. It is sometimes available in health stores or in the pharmacy section of the supermarket. It is usually found combined with other food ingredients. Soy protein shake powder, for example, is a mixture of soy protein isolate with flavors, minerals and vitamins.

Product type: Concentrates
Soy protein concentrate is about 70% soy protein and is basically soybean without the water soluble carbohydrates. It is made by removing part of the carbohydrates (sugars) from dehulled and defatted soybeans.
Soy protein concentrate retains most of the fiber of the original soybean. Soy protein concentrate is widely used as functional or nutritional ingredient in a wide variety of food products, mainly in baked foods, breakfast cereals and in some meat products. Soy protein concentrate is used in meat and poultry products to increase water and fat retention, and to improve nutritional values (more protein, less fat).

Soy protein concentrates are available in different forms; granules, flour and spray dried. Because they are very digestible, they are well-suited for children, pregnant and lactating women and the elderly. They are also used in pet foods, milk replacers for calves and pigs, and even used for some non-food applications.

Product type: Flours
Soy flour, is made by grinding soybeans, into a fine powder. It comes in three forms: natural or full-fat (contains natural oils); defatted (oils removed) with 50% protein content and with either high water solubility or low water solublity; and lecithinated (lecithin added). As soy flour is gluten-free, yeast-raised breads made with soy flour are dense in texture.

Soy grits are similar to soy flour except that the soybeans have been toasted and cracked into coarse pieces.

Soy protein may prevent heart problems and many countries allow health claims for foods that are rich in soy protein.

A soy protein health claim is allowed in the United States if a serving of the food meets the following conditions:

  • More than 6.25 grams of soy protein
  • Usually less than 3 grams of fat
  • Less than 1 gram of saturated fat
  • Less than 20 milligrams of cholesterol
  • Less than 480 milligrams of sodium

There are conflicting studies concerning the phytoestrogens contained in soy protein that bind to estrogen receptors in the body and their effect on the risk of certain forms of cancer.

In 1995, the New England Journal of Medicine(Vol.333, No. 5) published a report from the University of Kentucky entitled, "Meta-Analysis of the Effects of Soy Protein Intake on Serum Lipids." It was financed by the PTI division of DuPont, "The Solae Co." St. Louis. This meta-analysis concluded that soy protein is correlated with significant decreases in serum cholesterol, Low Density Lipoprotein LDL (bad) cholesterol and triglyceride concentrations. However, High Density Lipoprotein HDL (good) cholesterol did not increase. Soy phytoestrogens (isoflavones: genistein and daidzein) adsorbed onto the soy protein were suggested as the agent reducing serum cholesterol levels. On the basis of this research PTI, in 1998, filed a petition with FDA for a health claim that soy protein may reduce cholesterol and the risk of heart disease.

The FDA granted this health claim for soy:"25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease." One serving,(1 cup or 240 mL) of soy milk, for instance, contains 6 or 7 grams of soy protein.

In, January ,2006 an American Heart Association review (in the journal "Circulation") of a decade long study of soy protein benefits casts doubt on the FDA allowed "Heart Healthy" claim for soy protein. The panel also found that soy isoflavones DO NOT reduce post menopause "hot flashes" in women nor do isoflavones help prevent cancers of the breast, uterus or prostate. The original paper in the journal, Circulation: January 17,2006

Textured Soy Protein
TSP is made by forming a dough from high nitrogen solubility index (NSI) defatted soy flour with water in a screw type extruder such as the Wenger and heating with or without added steam. The dough is extruded through a die into various possible shapes; granules, flakes, chunks, goulash, steakettes (schnitzle), etc., and dried in an oven. TSP made from soy flour contains 50% soy protein and needs to be rehydrated, before use, at a weight ratio of 1 TSP:2 WATER. However, TSP when made from soy concentrate contains 70% protein and can be rehydrated at a ratio of 1:3. It can be used as a meat replacement or supplement. The extrusion technology changes the structure of the soy protein, resulting in a fibrous spongy matrix that is similar in texture to meat.

While TSP has a shelf life of more than a year when stored dry at room temperature, it should be used at once or stored for no more than three days in the refrigerator after rehydration. It is usually rehydrated with cold or hot water, but a bit of vinegar or lemon juice can be added to quicken the process.
TSP can replace ground beef in most recipes, completely or partly. It can also replace up to 33% "tuna" fish in tuna salad. It is high in protein and low in fat and sodium. It is also a good source of fiber and isoflavones.


  Copyright © 2006 Andy's Market. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Soy Protein".

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