Editing Soybean (section)

====Protein====
{{further|Complete protein|Protein quality|Soy protein}}
Most soy protein is a relatively heat-stable storage protein. This heat stability enables soy food products requiring high temperature cooking, such as [[tofu]], [[soy milk]] and [[textured vegetable protein]] (soy flour) to be made.  [[Soy protein]] is essentially identical to the protein of other [[legume]] seeds and [[pulse (legume)|pulse]]s.<ref>{{cite journal |last1=Derbyshire |first1=E. |last2=Wright |first2=D.J. |last3=Boulter |first3=D. |title=Legumin and Vicilin, Storage Proteins of Legume Seeds |journal=[[Phytochemistry (journal)|Phytochemistry]] |volume=15 |issue=1 |pages=3–24 |year=1976 |doi=10.1016/S0031-9422(00)89046-9|bibcode=1976PChem..15....3D }}</ref><ref>{{cite journal |pmid=16748534 |pmc=1274878 |year=1949 |last1=Danielsson |first1=C.E. |title=Seed Globulins of the Gramineae and Leguminosae |volume=44 |issue=4 |pages=387–400 |journal=The Biochemical Journal |doi=10.1042/bj0440387 }}</ref>

Soy is a good source of protein for vegetarians and [[Veganism|vegans]] or for people who want to reduce the amount of meat they eat, according to the [[Food and Drug Administration (United States)|US Food and Drug Administration]]:<ref name="fda-chd">{{Cite web |url=https://www.gpo.gov/fdsys/pkg/FR-1999-10-26/pdf/99-27693.pdf |title=Food Labeling: Health Claims; Soy Protein and Coronary Heart Disease; Docket No. 98P–0683 |publisher=US Food and Drug Administration; Federal Register, Vol. 64, No. 206 |location=Washington, DC |date=26 October 1999}}</ref>

{{Blockquote|Soy protein products can be good substitutes for animal products because, unlike some other beans, soy offers a 'complete' protein profile. ... Soy protein products can replace animal-based foods—which also have complete proteins but tend to contain more fat, especially saturated fat—without requiring major adjustments elsewhere in the diet.}}

Although soybeans have high protein content, soybeans also contain high levels of [[Protease inhibitor (biology)|protease inhibitors]], which can prevent digestion.<ref name="pmid16001874">{{cite journal |vauthors=Gilani GS, Cockell KA, Sepehr E |title=Effects of antinutritional factors on protein digestibility and amino acid availability in foods |journal=[[Journal of AOAC International]] |volume=88 |issue=3 |pages=967–987 |year=2005 |doi=10.1093/jaoac/88.3.967 |url=https://www.researchgate.net/publication/7742226 |pmid=16001874 |doi-access=free }}</ref> Protease inhibitors are reduced by cooking soybeans, and are present in low levels in soy products such as [[tofu]] and [[soy milk]].<ref name="pmid16001874" />

The [[PDCAAS|Protein Digestibility Corrected Amino Acid Score]] (PDCAAS) of soy protein is the nutritional equivalent of meat, eggs, and [[casein]] for human growth and health. Soybean protein isolate has a [[biological value]] of 74, whole soybeans 96, soybean milk 91, and eggs 97.<ref name="1991Report">{{cite book|title=Protein Quality Evaluation: Report of the Joint FAO/WHO Expert Consultation|publisher=Food and Agriculture Organization of the United Nations (Food and Nutrition Paper No. 51)|location=Bethesda, MD |year=1989|isbn=978-92-5-103097-4}}</ref>

[[File:Graded Seed.jpg|upright=0.9|thumb|Graded seed]]
All [[spermatophytes]], except for the family of grasses and cereals ([[Poaceae]]), contain 7S (vicilin) and 11S (legumin) soy protein-like globulin storage proteins; or only one of these [[globulin]] proteins. S denotes [[Svedberg]], sedimentation coefficients. Oats and rice are anomalous in that they also contain a majority of soybean-like protein.<ref name="Seed Proteins 1999">Seed Proteins; Peter R. Shewery and Rod Casey (Eds) 1999. Kluwer Academic Publishers, Dordrecht, The Netherlands</ref> Cocoa, for example, contains the 7S globulin, which contributes to cocoa/chocolate taste and aroma,<ref>{{cite web |url=http://openagricola.nal.usda.gov/Record/IND44131228 |title=Subunit structure of the vicilin-like globular storage... |work=usda.gov  |archive-url=https://web.archive.org/web/20150707233616/http://openagricola.nal.usda.gov/Record/IND44131228 |archive-date=July 7, 2015 }}</ref><ref>{{cite web |url=http://openagricola.nal.usda.gov/Record/IND20412524 |title=Cocoa-specific aroma precursors are generated by proteolytic... |work=usda.gov  |archive-url=https://web.archive.org/web/20150707234934/http://openagricola.nal.usda.gov/Record/IND20412524 |archive-date=July 7, 2015 }}</ref><ref>{{Cite web |last=Barringer |first=Sheryl |date=February 3, 2010 |url=http://library.osu.edu/assets/Uploads/ScienceCafe/Barringer020310.pdf |title=The Chemistry of Chocolate Flavor |website=[[Ohio State University]] |access-date=August 24, 2013 |archive-date=March 24, 2012 |archive-url=https://web.archive.org/web/20120324131437/http://library.osu.edu/assets/Uploads/ScienceCafe/Barringer020310.pdf |quote=Two proteases: aspartic endopeptidase and serine carboxy-(exo)peptidase on vicilin (7S)-class globulin storage proteins.}}</ref> whereas coffee beans (coffee grounds) contain the 11S globulin responsible for coffee's aroma and flavor.<ref>{{cite journal |title=Comparative Proteomical Analysis of Zygotic Embryo and Endosperm from ''Coffea arabica'' Seeds |first1=Lívia L. |last1=Koshino |first2=Clarissa P. |last2=Gomes |first3=Luciano P. |last3=Silva |first4=Mirian T.S. |last4=Eira |first5=Carlos |last5=Bloch Jr. |first6=Octávio L. |last6=Franco |first7=Ângela |last7=Mehta |date=November 26, 2008 |journal=[[J. Agric. Food Chem.]] |volume=56 |issue=22 |pages=10922–26 |doi=10.1021/jf801734m |pmid=18959416 |bibcode=2008JAFC...5610922K |url=http://www.alice.cnptia.embrapa.br/alice/handle/doc/190361}}</ref><ref>{{cite journal |first1=Lívia L. |last1=Koshino |first2=Clarissa P. |last2=Gomes |first3=Luciano P. |last3=Silva |first4=Mirian T. S. |last4=Eira |first5=Carlos Jr. |last5=Bloch |first6=Octávio L. |last6=Franco |first7=Ângela |last7=Mehta |date=November 26, 2008 |title=Comparative Proteomical Analysis of Zygotic Embryo and Endosperm from Coffea arabica Seeds |journal=[[Journal of Agricultural and Food Chemistry]] |volume=56 |issue=22 |pages=10922–10926 |url=http://www.alice.cnptia.embrapa.br/bitstream/doc/880533/1/Comparativeproteomical.pdf |access-date=August 24, 2013 |archive-url=https://web.archive.org/web/20131203144038/http://www.alice.cnptia.embrapa.br/bitstream/doc/880533/1/Comparativeproteomical.pdf |archive-date=December 3, 2013  |doi=10.1021/jf801734m |pmid=18959416 |bibcode=2008JAFC...5610922K }}</ref>

Vicilin and legumin proteins belong to the [[cupin superfamily]], a large family of functionally diverse proteins that have a common origin and whose evolution can be followed from bacteria to eukaryotes including animals and higher plants.<ref>{{cite journal |title=Evolution of seed storage globulins and cupin superfamily |doi=10.1134/S0026893311030162 |volume=45 |issue=4 |journal=[[Molecular Biology (journal)|Molecular Biology]] |pages=529–35 |year=2011 |last1=Shutov |first1=A.D. |pmid=21954589 |s2cid=26111362 }}</ref>

2S [[albumins]] form a major group of homologous storage proteins in many [[dicot]] species and in some [[monocots]] but not in grasses (cereals).<ref name="ReferenceA">{{cite journal |last1=Youle |first1=RJ |last2=Huang |first2=AHC |year=1981 |title=Occurrence of low molecular weight and high cysteine containing albumin storage proteins in oilseed of diverse species |journal=[[American Journal of Botany]] |volume=68 |issue=1 |pages=44–48 |doi=10.2307/2442990 |jstor=2442990 }}</ref> Soybeans contain a small but significant 2S storage protein.<ref>{{cite journal |pmc=2570561 |pmid=18949071 |doi= 10.2174/1874091X00802010016  |doi-access=free|volume=2 |title=2S Albumin Storage Proteins: What Makes them Food Allergens? |year=2008 |journal=[[Open Biochemistry Journal]] |pages=16–28 |last1=Moreno |first1=FJ |last2=Clemente |first2=A}}</ref><ref name="Seber-et-al-2012">{{cite journal |pmc=3326064 |pmid=22514740 |doi=10.1371/journal.pone.0035409 |volume=7 |issue=4 |title=Scalable purification and characterization of the anticancer lunasin peptide from soybean |year=2012 |journal=[[PLOS ONE]] |pages=e35409 |last1=Seber |first1=LE |last2=Barnett |first2=BW |last3=McConnell |first3=EJ |bibcode=2012PLoSO...735409S |doi-access=free }}</ref><ref>{{Cite web |url=https://www.sciencedaily.com/releases/2009/12/091202153946.htm |title=Soy peptide lunasin has anti-cancer, anti-inflammatory properties |website=ScienceDaily}}</ref> 2S albumin are grouped in the [[prolamin]] superfamily.<ref>{{cite web |url=http://www.meduniwien.ac.at/allergens/allfam/factsheet.php?allfam_id=AF050 |title=AllFam – AllFam Allergen Family Factsheet |work=meduniwien.ac.at  |archive-url=https://web.archive.org/web/20160304045912/http://www.meduniwien.ac.at/allergens/allfam/factsheet.php?allfam_id=AF050 |archive-date=March 4, 2016 }}</ref> Other allergenic proteins included in this 'superfamily' are the non-specific [[plant lipid transfer proteins]], [[alpha amylase inhibitor]], [[trypsin inhibitors]], and prolamin storage proteins of cereals and grasses.<ref name="Seed Proteins 1999" />

[[Peanut]]s, for instance, contain 20% 2S albumin but only 6% 7S globulin and 74% 11S.<ref name="ReferenceA" /> It is the high 2S albumin and low 7S globulin that is responsible for the relatively low lysine content of peanut protein compared to soy protein.