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Malic acid
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<h2 id="etymology">Etymology</h2> <p>The word 'malic' is derived from Latin <i>mālum</i>, meaning 'apple'. The related Latin word <i>mālus</i>, meaning 'apple tree', is used as the name of the genus <i><a href="/facts/Malus/MKp2k7Mq">Malus</a></i>, which includes all apples and crabapples;<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> and is the origin of other <a href="/facts/Taxonomy_(biology)/Qkg8wuyw">taxonomic</a> classifications such as <a href="/facts/Maloideae/rspDo3p2">Maloideae</a>, <a href="/facts/Malinae/Kf6gDCJC">Malinae</a>, and <a href="/facts/Maleae/qP0cyuI7">Maleae</a>. </p> <h2 id="biochemistry">Biochemistry</h2> <p>L-Malic acid is the naturally occurring form, whereas a mixture of L- and D-malic acid is produced synthetically. </p> <p>Malate plays an important role in <a href="/facts/Biochemistry/fa2pWEBp">biochemistry</a>. In the <a href="/facts/C4_carbon_fixation/2dLTxsae">C4 carbon fixation</a> process, malate is a source of <a href="/facts/Carbon_dioxide/xGzpppEp">CO2</a> in the <a href="/facts/Calvin_cycle/M1bIgQb9">Calvin cycle</a>. In the <a href="/facts/Citric_acid_cycle/EGJL9NXP">citric acid cycle</a>, (<i>S</i>)-malate is an intermediate, formed by the addition of an <a href="/facts/Hydroxy_group/1Hs2QAEv">-OH</a> group on the <i>si</i> face of fumarate. It can also be formed from pyruvate via <a href="/facts/Anaplerotic_reactions/dpCVjnBY">anaplerotic reactions</a>. </p><p>Malate is also synthesized by the <a href="/facts/Carboxylation/8zNzYvnP">carboxylation</a> of <a href="/facts/Phosphoenolpyruvate/CeUbr30F">phosphoenolpyruvate</a> in the guard cells of plant leaves. Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the <a href="/facts/Water_potential/ndU4I5Hz">solute potential</a>, allowing water to enter the cell and promote aperture of the stomata. </p> <h2 id="in-food">In food</h2> <p>Malic acid was first isolated from <a href="/facts/Apple_juice/njD9HdN9">apple juice</a> by <a href="/facts/Carl_Wilhelm_Scheele/kcKBwyXa">Carl Wilhelm Scheele</a> in 1785.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> <a href="/facts/Antoine_Lavoisier/UheVQrhu">Antoine Lavoisier</a> in 1787 proposed the name <i>acide malique</i>, which is derived from the <a href="/facts/Latin/pM3Kge85">Latin</a> word for apple, <i>mālum</i>—as is its <a href="/facts/Genus/m8EFjSms">genus</a> name <i><a href="/facts/Malus/MKp2k7Mq">Malus</a></i>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> In German it is named <i>Äpfelsäure</i> (or <i>Apfelsäure</i>) after plural or singular of a sour thing from the apple fruit, but the salt(s) are called <i>Malat(e)</i>. Malic acid is the main acid in many fruits, including <a href="/facts/Apricot/xCVFYtMK">apricots</a>, <a href="/facts/Blackberries/MVD1DHFR">blackberries</a>, <a href="/facts/Blueberries/2xtgLU6Y">blueberries</a>, <a href="/facts/Cherries/uVbsknBg">cherries</a>, <a href="/facts/Grape/HaCaS4bT">grapes</a>, <a href="/facts/Mirabelle/yPq2sqRm">mirabelles</a>, <a href="/facts/Peach/I7FLcBTU">peaches</a>, <a href="/facts/Pear/pRAKLrdK">pears</a>, <a href="/facts/Plum/w05NWXGc">plums</a>, and <a href="/facts/Quince/Hq0eoUp0">quince</a>,<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> and is present in lower concentrations in other fruits, such as <a href="/facts/Citric_acid/EgKGQBdl">citrus.</a> It contributes to the sourness of unripe apples. Sour apples contain high proportions of the acid. It is present in <a href="/facts/Grape/HaCaS4bT">grapes</a> and in most wines with concentrations sometimes as high as 5 g/L.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> It confers a tart taste to <a href="/facts/Wine/przCrC98">wine</a>; the amount decreases with increasing fruit <a href="/facts/Ripeness_(wine)/KrFE6W7m">ripeness</a>. The taste of malic acid is very clear and pure in <a href="/facts/Rhubarb/DDhM5G5U">rhubarb</a>, a plant for which it is the primary flavor. It is also the compound responsible for the tart flavor of <a href="/facts/Sumac/ABdDzFAD">sumac</a> spice. It is also a component of some artificial <a href="/facts/Vinegar/yC27CDkw">vinegar</a> flavors, such as "salt and vinegar" flavored potato chips.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>The process of <a href="/facts/Malolactic_fermentation/wPCGSXzW">malolactic fermentation</a> converts malic acid to much milder <a href="/facts/Lactic_acid/BsVRFx7s">lactic acid</a>. Malic acid occurs naturally in all fruits and many vegetables, and is generated in fruit metabolism.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p><p>Malic acid, when added to food products, is denoted by <a href="/facts/E_number/n3VSY29I">E number</a> E296. It is sometimes used with or in place of the less sour <a href="/facts/Citric_acid/EgKGQBdl">citric acid</a> in sour sweets. These sweets are sometimes labeled with a warning stating that excessive consumption can cause irritation of the mouth. It is approved for use as a <a href="/facts/Food_additive/jGk8zjn8">food additive</a> in the EU,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> US<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> and Australia and New Zealand<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> (where it is listed by its <a href="/facts/INS_number/sP26VTNF">INS number</a> 296). </p><p>Malic acid contains 10 kJ (2.39 kilocalories) of energy per gram.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h2 id="production-and-main-reactions">Production and main reactions</h2> <p><a href="/facts/Racemic/STEagtrD">Racemic</a> malic acid is produced industrially by the double hydration of <a href="/facts/Maleic_anhydride/KfBTU8n4">maleic anhydride</a>. In 2000, American production capacity was 5,000 tons per year. The <a href="/facts/Enantiomer/wjPv5J3y">enantiomers</a> may be separated by <a href="/facts/Chiral_resolution/tu0AIqGg">chiral resolution</a> of the racemic mixture. <i>S</i>-Malic acid is obtained by fermentation of <a href="/facts/Fumaric_acid/VDecBfLQ">fumaric acid</a>.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p><a href="/facts/Self-condensation/rnsHW3k4">Self-condensation</a> of malic acid in the presence of <a href="/facts/Fuming_sulfuric_acid/oyT7XMod">fuming sulfuric acid</a> gives the <a href="/facts/Pyrone/gp3yTctd">pyrone</a> <a href="/facts/Coumalic_acid/PxcyRYBw">coumalic acid</a>:<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> 2 HO2CCH(OH)CH2CO2H → HO2CC4H3O2 + 2 CO + 4 H2O <p><a href="/facts/Carbon_monoxide/CKuLtEMJ">Carbon monoxide</a> and water are liberated during this reaction. </p><p>Malic acid was important in the discovery of the <a href="/facts/Walden_inversion/6p72etqF">Walden inversion</a> and the <a href="/facts/Walden_cycle/6p72etqF">Walden cycle</a>, in which (−)-malic acid first is converted into (+)-chlorosuccinic acid by action of <a href="/facts/Phosphorus_pentachloride/oGLG4kDg">phosphorus pentachloride</a>. Wet <a href="/facts/Silver_oxide/XPGcRQ2E">silver oxide</a> then converts the chlorine compound to (+)-malic acid, which then reacts with PCl5 to the (−)-chlorosuccinic acid. The cycle is completed when silver oxide takes this compound back to (−)-malic acid. </p><p>L-malic acid is used to <a href="/facts/Chiral_resolution/tu0AIqGg">resolve</a> <a href="/facts/1-Phenylethylamine/1WlQczGI">α-phenylethylamine</a>, a versatile resolving agent in its own right.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> </p> <h2 id="plant-defense">Plant defense</h2> <p>Soil supplementation with <a href="/facts/Molasses/N8kE2HfI">molasses</a> increases microbial synthesis of malic acid. This is thought to occur naturally as part of <a href="/facts/Disease_suppressive_soils/0eR1ICb8">soil microbe suppression of disease</a>, so <a href="/facts/Soil_amendment/35DWU3Cc">soil amendment</a> with molasses can be used as a <a href="/facts/Crop/JoQKR5R8">crop</a> treatment in horticulture.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> </p> <h2 id="interactive-pathway-map">Interactive pathway map</h2> <p><i>Click on genes, proteins and metabolites below to link to respective articles.</i><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Acids_in_wine/lIF43ur4">Acids in wine</a></li> <li><a href="/facts/Citrate%25E2%2580%2593malate_shuttle/kGpVkkE6">Citrate–malate shuttle</a></li> <li><a href="/facts/Crassulacean_acid_metabolism/hnwHeIJd">Crassulacean acid metabolism</a></li> <li><a href="/facts/Malate%25E2%2580%2593aspartate_shuttle/SyPXrDMF">Malate–aspartate shuttle</a></li> <li><a href="/facts/Maleic_acid/cdMjU0Lb">Maleic acid</a>, resulting from malic acid dehydration</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://www.aim.env.uea.ac.uk/aim/accent2/inputpage.php">Calculator: Water and solute activities in aqueous malic acid</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Peffley, Ellen. "Peffley: Crabapples steal the show in autumn". Lubbock Avalanche-Journal. Retrieved 2022-08-08. <a href="https://www.lubbockonline.com/story/lifestyle/home-garden/2021/11/23/peffley-crabapples-steal-show-autumn/8716819002/" target="_blank">https://www.lubbockonline.com/story/lifestyle/home-garden/2021/11/23/peffley-crabapples-steal-show-autumn/8716819002/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Carl Wilhelm Scheele (1785) "Om Frukt- och Bår-syran" (On fruit and berry acid), Kongliga Vetenskaps Academiens Nya Handlingar (New Proceedings of the Royal Academy of Science), 6 : 17-27. From page 21: " ... vil jag hådanefter kalla den Åple-syran." ( ... I will henceforth call it apple acid.) <a href="https://books.google.com/books?id=8nVJAAAAcAAJ&pg=PA17" target="_blank">https://books.google.com/books?id=8nVJAAAAcAAJ&pg=PA17</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>de Morveau, Lavoisier, Bertholet, and de Fourcroy, Méthode de Nomenclature Chimique (Paris, France: Cuchet, 1787), p. 108. <a href="http://babel.hathitrust.org/cgi/pt?id=nyp.33433001042179;view=1up;seq=118" target="_blank">http://babel.hathitrust.org/cgi/pt?id=nyp.33433001042179;view=1up;seq=118</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Jensen, William B. (June 2007). "The Origin of the Names Malic, Maleic, and Malonic Acid". Journal of Chemical Education. 84 (6): 924. Bibcode:2007JChEd..84..924J. doi:10.1021/ed084p924. ISSN 0021-9584. <a href="https://pubs.acs.org/doi/abs/10.1021/ed084p924" target="_blank">https://pubs.acs.org/doi/abs/10.1021/ed084p924</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Tabelle I of "Fruchtsäuren". Wissenschaft Online Lexikon der Biologie. Archived from the original on May 15, 2016. <a href="https://web.archive.org/web/20170902120747/http://www.spektrum.de/lexika/showpopup.php?lexikon_id=9&art_id=25817&nummer=9023" target="_blank">https://web.archive.org/web/20170902120747/http://www.spektrum.de/lexika/showpopup.php?lexikon_id=9&art_id=25817&nummer=9023</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Ough, C. S. (1988). Methods for analysis of musts and wines (2nd ed.). New York: J. Wiley. p. 67. ISBN 0-471-62757-7. OCLC 16866762. <a href="0-471-62757-7" target="_blank">0-471-62757-7</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"The Science Behind Salt and Vinegar Chips". seriouseats.com. <a href="http://www.seriouseats.com/2012/09/the-best-salt-and-vinegar-chips-tasting-brands-most-acidic.html" target="_blank">http://www.seriouseats.com/2012/09/the-best-salt-and-vinegar-chips-tasting-brands-most-acidic.html</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Malic Acid Archived 2018-06-25 at the Wayback Machine, Bartek Ingredients (retrieved 2 February 2012) <a href="http://www.bartek.ca/malic_acid.html" target="_blank">http://www.bartek.ca/malic_acid.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>UK Food Standards Agency: "Current EU approved additives and their E Numbers". Retrieved 2011-10-27. <a href="http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist" target="_blank">http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"Food Additive Status List". FDA. 26 August 2021. Retrieved 5 May 2022. <a href="https://www.fda.gov/food/food-additives-petitions/food-additive-status-list" target="_blank">https://www.fda.gov/food/food-additives-petitions/food-additive-status-list</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Australia New Zealand Food Standards Code"Standard 1.2.4 - Labelling of ingredients". 8 September 2011. Retrieved 2011-10-27. <a href="http://www.comlaw.gov.au/Details/F2011C00827" target="_blank">http://www.comlaw.gov.au/Details/F2011C00827</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Greenfield, Heather; Southgate, D.A.T. (2003). Food composition data: production, management and use (2 ed.). Rome: Food and Agriculture Organization of the United Nations. p. 146. ISBN 978-92-5-104949-5. Retrieved 10 February 2014. <a href="978-92-5-104949-5" target="_blank">978-92-5-104949-5</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Karlheinz Miltenberge. "Hydroxycarboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_507. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Richard H. Wiley, Newton R. Smith (1951). "Coumalic acid". Organic Syntheses. 31: 23. doi:10.15227/orgsyn.031.0023. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>A. W. Ingersoll (1937). "D- and l-α-Phenylethylamine". Organic Syntheses. 17: 80. doi:10.15227/orgsyn.017.0080. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Rosskopf, Erin; Di Gioia, Francesco; Hong, Jason C.; Pisani, Cristina; Kokalis-Burelle, Nancy (2020-08-25). "Organic Amendments for Pathogen and Nematode Control". Annual Review of Phytopathology. 58 (1). Annual Reviews: 277–311. doi:10.1146/annurev-phyto-080516-035608. ISSN 0066-4286. PMID 32853099. S2CID 221360634. <a href="/wiki/Annual_Review_of_Phytopathology" target="_blank">/wiki/Annual_Review_of_Phytopathology</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>The interactive pathway map can be edited at WikiPathways: "GlycolysisGluconeogenesis_WP534". <a href="http://www.wikipathways.org/index.php/Pathway:WP534" target="_blank">http://www.wikipathways.org/index.php/Pathway:WP534</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> </ol>