Editing Gelatin (section)

== Characteristics ==

=== Properties ===
Gelatin is a collection of peptides and [[protein]]s produced by partial [[hydrolysis]] of collagen extracted from the skin, bones, and [[connective tissue]]s of animals such as domesticated cattle, chicken, pigs, and fish. During hydrolysis, some of the bonds between and within component proteins are broken. Its chemical composition is, in many aspects, closely similar to that of its parent collagen.<ref name="Ward2">{{cite book|last=Ward|first=A.G.|title=The Science and Technology of Gelatin|author2=Courts, A.|publisher=Academic Press|year=1977|isbn=978-0-12-735050-9|location=New York}}</ref> Photographic and pharmaceutical grades of gelatin generally are sourced from cattle bones and pig skin. Gelatin is classified as a [[hydrogel]].

[[File:Amino_Acid_Composition_in_Gelatin_chart.png|right|thumb|[[Amino acid]] composition]]
Gelatin is nearly tasteless and odorless with a colorless or slightly yellow appearance.<ref name=":02">Budavari, S. (1996). ''Merck Index, (12th ed.)'' Whitehouse Station, NJ: Merck.</ref><ref>Food and Nutrition Board, National Academy of Sciences. (1996). ''Food Chemicals Codex 4th Ed''. Washington, DC: National Academy Press.</ref> It is transparent and brittle, and it can come as sheets, flakes, or as a powder.<ref name=":02" /> [[Polar solvent]]s like hot water, glycerol, and acetic acid can dissolve gelatin, but it is insoluble in organic solvents like alcohol.<ref name=":02" /> Gelatin absorbs 5–10 times its weight in water to form a gel.<ref name=":02" /> The gel formed by gelatin can be melted by reheating, and it has an increasing viscosity under stress ([[Thixotropy|thixotropic]]).<ref name=":02" /> The upper melting point of gelatin is below [[human body temperature]], a factor that is important for [[mouthfeel]] of foods produced with gelatin.<ref name="Cole2">{{cite book|title=Encyclopedia of Food Science and Technology|date=2000|publisher=John Wiley & Sons|isbn=978-0-471-19255-8|editor=Francis, Frederick J.|edition=2nd|pages=1183–88|chapter=Gelatin|chapter-url=http://www.gelatin.co.za/gltn1.html|archive-url=https://web.archive.org/web/20050829055205/http://www.gelatin.co.za/gltn1.html|archive-date=29 August 2005|url-status=live|df=dmy-all}}</ref> The [[viscosity]] of the gelatin-water mixture is greatest when the gelatin concentration is high and the mixture is kept cool at about {{convert|4|C}}. Commercial gelatin will have a gel strength of around 90 to 300 grams Bloom using the [[Bloom (test)|Bloom]] test of gel strength.<ref>Igoe, R.S. (1983). ''Dictionary of Food Ingredients.'' New York: Van Nostrand Reinhold.</ref> Gelatin's strength (but not viscosity) declines if it is subjected to temperatures above {{convert|100|C}}, or if it is held at temperatures near 100&nbsp;°C for an extended period of time.<ref>{{Cite web |title=6 Unexpected Factors That Can Ruin Your Gelatin Desserts |url=https://www.seriouseats.com/how-to-avoid-problems-with-gelatin-dessert-baking |first1=Stella |last1=Parks |website=Serious Eats |language=en}}</ref><ref>[https://web.archive.org/web/20170509225608/http://www.finecooking.com/article/the-science-of-gelatin The Science of Gelatin – FineCooking]</ref>

Gelatins have diverse melting points and gelation temperatures, depending on the source. For example, gelatin derived from fish has a lower melting and gelation point than gelatin derived from beef or pork.<ref name="omri3">{{cite web|title=National Organic Standards Board Technical Advisory Panel Review: Gelatin processing|url=http://www.omri.org/Gelatin-TAP.pdf|archive-url=https://web.archive.org/web/20070927014944/http://www.omri.org/Gelatin-TAP.pdf|archive-date=27 September 2007|work=omri.org|df=dmy}}</ref>

=== Composition ===
When dry, gelatin consists of 98–99% protein, but it is not a nutritionally complete protein since it is missing [[tryptophan]] and is deficient in [[isoleucine]], [[threonine]], and [[methionine]].<ref>Potter, N.N. and J.H. Hotchkiss. (1998). ''Food Science (5th ed.)'' Gaithersburg, MD: Aspen.{{page needed|date=November 2024}}</ref>{{page needed|date=November 2024}} The [[amino acid]] content of hydrolyzed collagen is the same as collagen. Hydrolyzed collagen contains 19 amino acids, predominantly [[glycine]] (Gly) 26–34%, [[proline]] (Pro) 10–18%, and [[hydroxyproline]] (Hyp) 7–15%, which together represent around 50% of the total amino acid content.<ref name=":12">Poppe, J. (1997). Gelatin, in A. Imeson (ed.) ''Thickening and Gelling Agents for Food (2nd ed.)'': 144–68. London: Blackie Academic and Professional.</ref> Glycine is responsible for close packing of the chains. Presence of proline restricts the conformation. This is important for gelation properties of gelatin.<ref>{{cite web|title=Gelatin Handbook|url=http://www.gelatin-gmia.com/images/GMIA_Gelatin_Manual_2012.pdf|archive-url=https://web.archive.org/web/20170516200308/http://www.gelatin-gmia.com/images/GMIA_Gelatin_Manual_2012.pdf|archive-date=16 May 2017|access-date=27 September 2017|df=dmy-all}}</ref> Other amino acids that contribute highly include: [[alanine]] (Ala) 8–11%; [[arginine]] (Arg) 8–9%; [[aspartic acid]] (Asp) 6–7%; and [[glutamic acid]] (Glu) 10–12%.<ref name=":12" />