Soy protein is a protein that is isolated from soybean. It is made from soybean meal that has been dehulled and defatted. Dehulled and defatted soybeans are processed into three kinds of high protein commercial products: soy flour, concentrates, and isolates. Soy protein isolate has been used since 1959 in foods for its functional properties.
Soy protein is generally regarded as being concentrated in 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. Soybeans contain a small but newly very significant 2S Albumin storage protein. Legume proteins, such as soy and pulses, belong to the globulin family of seed storage proteins called legumin and vicilins, or in the case of soybeans, glycinin and beta-conglycinin. Soybeans also contain biologically active or metabolic proteins, such as enzymes, trypsin inhibitors, hemagglutinins, and cysteine proteases very similar to papain. 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 ≈ 30-120 g/l) from dehulled and defatted soybeans that have undergone only a minimal heat treatment so the protein is close to being native or undenatured.
Soy protein has been available since 1936 for its functional properties. In that year, organic chemist Percy Lavon Julian designed the world's first plant for the isolation of industrial-grade soy protein called alpha protein. The largest use of industrial-grade protein was, and still is, for paper coatings, in which it serves as a pigment binder. However, 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 that Henry Ford wore on special occasions. The plant's eventual daily output of 40 tons of soy protein isolate made the Soya Products Division into Glidden's most profitable division.
At the start of the Second World War, Glidden sent a sample of Julian's isolated soy (alpha) protein to National Foam System Inc. (today a unit of Kidde Fire Fighting) which used it to develop Aero-Foam, used by the U.S. Navy for fire fighting and referred to as "bean soup". While not exactly the brainchild of Dr. Julian, it was the meticulous care given to the preparation of the soy protein that made the fire fighting foam possible. When a hydrolysate of isolated soy protein was fed into a water stream, the mixture was converted into a foam by means of an aerating nozzle. The soy protein foam was used to smother oil and gasoline fires aboard ships, and was particularly useful on aircraft carriers. It saved the lives of thousands of sailors.
In 1958, Central Soya of Fort Wayne, Indiana, acquired Julian's Soy Products Division (Chemurgy) of the Glidden Paint Company, Chicago. Central Soya's Bunge Protein Division, in January, 2003, joined/merged with DuPont's soy protein business Solae, which in 1997 had acquired Ralston Purina's soy division, Protein Technologies International (PTI) in St. Louis. On May 1, 2012 DuPont announced its complete acquisition of Solae from Bunge,
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.:227–28 An edible soy isolate and edible spun soy fiber have also been available since 1960 from the Ralston Purina Company in St. Louis, who had hired Boyer and Calvert. In 1988, PTI became the world's leading maker of isolated soy protein.
Soy protein is used in various foods, such as salad dressings, soups, meat analogues, beverage powders, cheeses, nondairy creamer, frozen desserts, whipped topping, infant formulas, breads, breakfast cereals, pastas, and pet foods.
Soy flour or defatted soy flour (50% protein) glue which originally replaced the more expensive casein glue for Douglas fir plywood is re-emerging as the glue of choice to replace toxic urea formaldehyde and phenol formaldehyde resin glues with a formaldehyde-free soy glue. Soy protein is used for emulsification and texturizing. Specific applications include adhesives, asphalts, resins, cleaning materials, cosmetics, inks, pleather, paints, paper coatings, pesticides/fungicides, plastics, polyesters, and textile fibres.
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 liquid is acidified to a pH range of 4-5. The precipitated protein-curd is collected and separated from the whey by centrifuge. 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 or more 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 (which may involve calcium or magnesium cations), and leaching with hot water of heat-treated 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 tonne of defatted soybean flakes will yield about 750 kg of soybean protein concentrate.
Soy protein isolate is a highly refined or purified form of soy protein with a minimum protein content of 90% on a moisture-free basis. It is made from defatted soy flour which has had most of the nonprotein components, fats and carbohydrates removed. Because of this, it has a neutral flavor and will cause less flatulence than soy flours.:11
Pure soy protein isolate is used mainly by the food industry. 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 concentrate is about 70% soy protein and is basically defatted soy flour without the water-soluble carbohydrates. It is made by removing part of the carbohydrates (soluble sugars) from dehulled and defatted soybeans.
Soy protein concentrate retains most of the fiber of the original soybean. It 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 replacements for babies (human and livestock), and even used for some nonfood applications.
Soy flour is made by grinding soybeans into a fine powder. It comes in three forms: whole or full-fat (contains natural oils); defatted (oils removed) with 50% protein content and with either high water solubility or low water solubility; and lecithinated (lecithin added). A history of soy flour and grits has been published. 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 the soybeans have been toasted and cracked into coarse pieces.
Soybean protein is a complete protein since it provides all of the essential amino acids for human nutrition. Soybean protein is essentially identical to that of other legume pulses (that is to say, legume proteins in general consist of 7S and 11S storage proteins), and is one of the least expensive sources of dietary protein. For this reason, soy is important to many vegetarians and vegans.
Soy flour contains 50% protein.
The digestibility of some soyfoods are as follows; steamed soybeans 65.3%, tofu 92.7%, soy milk 92.6%, and soy protein isolate 93–97%. Some studies on rats have indicated the biological value of soy protein isolates is comparable to animal proteins such as casein if enriched with the sulfur-containing amino acid methionine.
When measuring the nutritional value of protein, the original protein efficiency ratio (PER) method, first proposed by Thomas Burr Osborne and Lafayette Mendel in 1917, was the most widely used method until 1990. This method was found to be flawed for the biological evaluation of protein quality because the young rats used in the study had higher relative requirements for sulfur-containing amino acids than did humans. As such, the analytical method universally recognized by the FAO/WHO (1990), as well as the FDA, USDA, United Nations University and the National Academy of Sciences when judging the quality of protein is the protein digestibility-corrected amino acid score, as it is viewed as accurately measuring the correct relative nutritional value of animal and vegetable sources of protein in the diet. Based on this method, soy protein is considered to have a similar equivalent in protein quality to animal proteins. Egg white has a score of 1.00, soy concentrate 0.99, beef 0.92, and isolated soy protein 0.92. In 1990 at an FAO/WHO meeting, it was decided that proteins having values higher than 1.0 would be rounded or "leveled down" to 1.0, as scores above 1.0 are considered to indicate the protein contains essential amino acids in excess of the human requirements.
Another measure of a protein's use in nutrition is the biological value scale, which dates back to 1911; it relies on nitrogen retention as a measurement of protein quality. Soybean protein isolate has a biological value of 74. Whole soybean has a biological value of 96, and soy milk 91.
A meta-analysis concluded soy protein is correlated with significant decreases in serum cholesterol, low density lipoprotein (LDL) cholesterol and triglyceride concentrations. High density lipoprotein (HDL) cholesterol did not change. Although there is only preclinical evidence for a possible mechanism, the meta-analysis report stated that soy phytoestrogens – the isoflavones, genistein and daidzein – may be involved in reducing serum cholesterol levels.
In 1999, the US FDA granted a health claim for labeling of manufactured food products containing 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."
In 2006, an American Heart Association review of soy protein benefits indicated only weak confirmation for the cholesterol-lowering claim about soy protein. The panel also found soy isoflavones do not reduce postmenopause "hot flashes" in women, nor do isoflavones lower risk of cancers of the breast, uterus, or prostate. Among the conclusions, the authors stated, "In contrast, soy products such as tofu, soy butter, soy nuts, or some soy burgers should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat. Using these and other soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health."
In 2012, the European Food Safety Authority (EFSA) published a scientific opinion on isolated soy proteins and reduction of blood LDL-cholesterol concentrations.[dead link] EFSA concluded that a cause and effect relationship was not established between the consumption of soy protein and a reduction in blood LDL-cholesterol concentrations. In 2010, the EFSA had already rejected health claims that linked the consumption of soy protein to the maintenance or achievement of a normal body weight, the reduction of blood cholesterol concentrations, or the protection of DNA, proteins and lipids from oxidative damage.[dead link]
Role in the growth of the soybean plantEdit
Soy protein is generally regarded as stored protein held in discrete particles called "protein bodies" estimated to contain at least 60% to 70% of the total protein within the soybean seed. This protein is important to the growth of new soybean plants, and when the soybean seed germinates, 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 legumin (11S globulin fraction) and vicilins (7S globulin), or in the case of soybeans, glycinin and beta-conglycinin. Grains contain a third type of storage protein called gluten or "prolamines". Edestin, a legumin class reserve protein from hemp seeds have six identical subunits. There is one hexameric protein in the rhombohedral unit cell.
Soybeans also contain biologically active or metabolic proteins, such as enzymes, trypsin inhibitors, hemagglutinins, and cysteine proteases very similar to papain. 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 the protein is close to being native or undenatured. Soybeans are processed into three kinds of modern protein-rich products; soy flour, soy concentrate, and soy isolate.
For the 11S protein, glycinin, to fold properly into its hexagonal shape (containing six subunits, a hexamer), it must undergo a very limited proteolysis in a manner similar to the cleavage of a peptide from proinsulin to obtain active insulin.
Textured soy proteinEdit
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, and heating with or without steam. The dough is extruded through a die into various possible shapes: granules, flakes, chunks, goulash, steakettes (schnitzel), etc., and dried in an oven. TSP made from soy flour contains 50% soy protein and must 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 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.
Soy protein products such as TSP are used as low-cost substitutes in meat and poultry products. Food service, retail and institutional (primarily school lunch and correctional) facilities regularly use such "extended" products. Extension may result in diminished flavor, but fat and cholesterol are reduced. Vitamin and mineral fortification can be used to make soy products nutritionally equivalent to animal protein; the protein quality is already roughly equivalent. The soy-based meat substitute textured vegetable protein has been used for more than 50 years as a way of inexpensively and safely extending ground beef up to 30% for hamburgers, without reducing its nutritional value.
- "Info" (PDF). www.plantcell.org.
- Moreno, F. J.; Clemente, A. (2008). "2S Albumin Storage Proteins: What Makes them Food Allergens?". Open Biochem J. 2: 16–28. doi:10.2174/1874091X00802010016. PMC 2570561. PMID 18949071.
- Seber, L. E.; Barnett, B. W.; McConnell, E. J.; Hume, S. D.; Cai, J.; Boles, K.; Davis, K. R. (2012). "Scalable purification and characterization of the anticancer lunasin peptide from soybean". PLOS ONE. 7 (4): e35409. doi:10.1371/journal.pone.0035409. PMC 3326064. PMID 22514740.
- "The Gliden Company". www.soyinfocenter.com.
- "NMS 120" (PDF). www.sosrubberintl.com.
- "Archived copy" (PDF). Archived from the original (PDF) on 2011-10-03. Retrieved 2011-06-22.CS1 maint: archived copy as title (link)
- "PRODUCTION: Navy Bean Soup". Time. 1943-12-06. Retrieved 2010-05-23.
- "Archived copy". Archived from the original on 2012-05-09. Retrieved 2012-05-01.CS1 maint: archived copy as title (link)
- "Food ingredient solutions for the food industry - DuPont - Danisco". www.solae.com.
- William Shurtleff, Akiko Aoyagi History of Cooperative Soybean Processing in the United States: Extensively Annotated Bibliography and Sourcebook Soyinfo Center, 2008
- "Tofu ingredient yields formaldehyde-free glue for plywood and other wood products - American Chemical Society". American Chemical Society.
- "Old-new glue for plywood, composites". 26 August 2010.
- "Tofu ingredient used to create formaldehyde-free plywood glue". www.gizmag.com.
- "Sticking power from soya beans" (PDF). Retrieved 2018-09-17.
- "Documents" (PDF). www.fpl.fs.fed.us. 2014.
- "I.F. Laucks Co. and Soybean Glue". www.soyinfocenter.com.
- E.S. Sipos. Edible Uses of Soybean Protein Archived 2013-04-03 at the Wayback Machine
- Singh, Preeti; Kumar, R.; Sabapathy, S. N.; Bawa, A. S. (2008). "Functional and Edible Uses of Soy Protein Products". Comprehensive Reviews in Food Science and Food Safety. 7: 14–28. doi:10.1111/j.1541-4337.2007.00025.x.
- Shurtleff, W.; Aoyagi. A.. 2013. "History of Soy Flour, Grits and Flakes (510 CE to 2013)." Lafayette, California: Soyinfo Center. 2,053 pp. (6,616 references; 202 photographs and illustrations, Free online).
- Shurtleff, W.; Aoyagi. A.. 2012. "History of Roasted Whole Soy Flour (Kinako), Soy Coffee... (1540-2012)." Lafayette, California: Soyinfo Center. 709 pp. (1,420 references; 76 photographs and illustrations, Free online).
- "National Soybean Research Laboratory". Nsrl.uiuc.edu. Archived from the original on 2012-03-04. Retrieved 2011-09-29.
- "Soy: Health Claims for Soy Protein, Questions About Other Components".
- Derbyshire, E. et al.1976. Review: Legumin and vicilin, storage proteins of legume seeds" Phytochemistry 15:3.
- Lim 2012, p. 637.
- Liu, KeShun (1997-05-01). Soybeans : Chemistry, Technology, and Utilization (Hardcover). Springer. p. 532. ISBN 978-0-8342-1299-2.
Citation on p.391 from Watanabe, et al., 1971 (in Japanese)
- "Nutritional Value of Food Protein Products", I.E. Liener; In Smith and Circle, editors; "Soybeans: Chemistry and Technology." Published by The AVI Publishing Co. 1972. Westport, Connecticut.
- Hajos, G., et al., Effects of Proteolytic Modification and Methionine Enrichment On the Nutritional Value of Soya Albumins For Rats. Nutri. Biochem. 7:481-487, 1996.
- FAO/WHO (1991) Protein Quality Evaluation Report of Joint FAO/WHO Expert Consultation, Food and Agriculture Organization of the United Nations, FAO Food and Nutrition Paper No. 51, Rome.
- Schaafsma, G. (2000) 'The protein digestibility-corrected amino acid score. Journal of Nutrition 130, 1865S-1867S
- FAO/WHO . Expert consultation on protein quality evaluation. Food and Agriculture Organization of the United Nations, Rome.
- Protein Quality-Report of Joint FAO’/WHO Expert Consultation, Food and Agriculture Organisation, Rome, FAO Food and Nutrition Paper 51, 1991.
- Smith, A.K. and Circle, S.J.1972. Soybeans: Chemistry and Technology.Table7.7 page 219. AVI publishing.
- Anderson, JW; Johnstone, BM; Cook-Newell, ME (1995). "Meta-analysis of the effects of soy protein intake on serum lipids". New England Journal of Medicine. 333 (5): 276–82. doi:10.1056/NEJM199508033330502. PMID 7596371.
- "Soy Protein and Risk of Coronary Heart Disease (21 CFR 101.82); Guidance for Industry: A Food Labeling Guide (11. Appendix C: Health Claims)". US Food and Drug Administration. January 2013. Retrieved 20 January 2017.
- Sacks, F. M.; Lichtenstein, A; Van Horn, L; Harris, W; Kris-Etherton, P; Winston, M; American Heart Association Nutrition Committee. (February 2006). "Soy protein, isoflavones, and cardiovascular health: an American Heart Association Science Advisory for professionals from the Nutrition Committee". Circulation. 113 (7): 1034–44. doi:10.1161/CIRCULATIONAHA.106.171052. PMID 16418439.
- "Scientific Opinion on the substantiation of a health claim related to isolated soy protein and reduction of blood LDL-cholesterol concentrations pursuant to Article 14 of Regulation (EC) No 1924/2006". EFSA Journal. 10 (2): 2555. 2012. doi:10.2903/j.efsa.2012.2555.
- "Scientific Opinion on the substantiation of health claims related to soy protein and contribution to the maintenance or achievement of a normal body weight (ID 598), maintenance of normal blood cholesterol concentrations (ID 556) and protection of DNA, proteins and lipids from oxidative damage (ID 435) pursuant to Article 13(1) of Regulation (EC) No 1924/2006". EFSA Journal. 8 (10): 1812. 2010. doi:10.2903/j.efsa.2010.1812. ISSN 1831-4732.
- "Archived copy" (PDF). Archived from the original (PDF) on 2012-02-27. Retrieved 2010-03-17.CS1 maint: archived copy as title (link)
- Damodaran, Srinivasan (2001-06-15). Food proteins and their applications - Srinivasan Damodaran, Alain Paraf - Google Books. ISBN 978-0-8247-9820-8. Retrieved 2011-09-29.
- Patel, S.; Cudney, R.; McPherson, A. (January 1994). "Crystallographic characterization and molecular symmetry of edestin, a legumin from hemp". J. Mol. Biol. 235 (1): 361–3. doi:10.1016/S0022-2836(05)80040-3. PMID 8289257.
- Shewry, PR; Napier, JA; Tatham, AS (1995). "Seed storage proteins: Structures and biosynthesis". The Plant Cell. 7 (7): 945–56. doi:10.1105/tpc.7.7.945. PMC 160892. PMID 7640527.
- Scott, MP; Jung, R; Muntz, K; Nielsen, NC (1992). "A protease responsible for post-translational cleavage of a conserved Asn-Gly linkage in glycinin, the major seed storage protein of soybean". Proceedings of the National Academy of Sciences of the United States of America. 89 (2): 658–62. doi:10.1073/pnas.89.2.658. PMC 48298. PMID 1731337.
- Jung, R; Scott, MP; Nam, YW; Beaman, TW; Bassüner, R; Saalbach, I; Müntz, K; Nielsen, NC (1998). "The role of proteolysis in the processing and assembly of 11S seed globulins". The Plant Cell. 10 (3): 343–57. doi:10.1105/tpc.10.3.343. PMC 144002. PMID 9501109.
- Muramatsu, Masayoshi; Fukazawa, Chikafusa (1993). "A high-order structure of plant storage proprotein allows its second conversion by an asparagine-specific cysteine protease, a novel proteolytic enzyme". European Journal of Biochemistry. 215 (1): 123–32. doi:10.1111/j.1432-1033.1993.tb18014.x. PMID 8344272.
- Hoogenkamp, Henk W. (2005). Soy protein and formulated meat products. Wallingford, Oxon, UK: CABI Pub. ISBN 978-0-85199-864-0.
- Joseph G. Endres (2001). Soy Protein Products. AOCS Publishing. ISBN 978-1-893997-27-1.
- Circle, Sidney Joseph; Smith, Allan H. (1972). Soybeans: chemistry and technology. Westport, Conn: Avi Pub. Co. ISBN 978-0-87055-111-6.
- Liu, KeShun (1997). Soybeans : Chemistry, Technology, and Utilization. Gaithersburg, Md: Aspen Publishers. ISBN 978-0-8342-1299-2.
- Riaz, Mian N. (2006). Soy applications in food - Mian N. Riaz - Google Books. ISBN 978-0-8493-2981-4. Retrieved 2011-09-29.