Calcium diglutamate explained

Calcium diglutamate, sometimes abbreviated CDG and also called calcium biglutamate, is a compound with formula Ca(C5H8NO4)2. It is a calcium acid salt of glutamic acid. CDG is a flavor enhancer (E number E623) - it is the calcium analog of monosodium glutamate (MSG). Because the glutamate is the actual flavor-enhancer, CDG has the same flavor-enhancing properties as MSG but without the increased sodium content.[1] Notably, only the L isomer is used in flavouring as D-glutamate does not have an umami/savoury flavour.[2] [3]

As a soluble source of calcium ions, this chemical is also used as a first-aid treatment for exposure to hydrofluoric acid.[4]

Synthesis and reactions

Calcium di-glutamate can be prepared by reacting calcium carbonate with two molar equivalents of glutamic acid:[5]

CaCO3 + 2 HOOC(CH2)2CH(NH2)COOH → Ca(OOC(CH2)2CH(NH3)COO)2 + H2O + CO2↑

Concentration of the solution to a syrup under reduced pressure, followed by gradual crystallisation, affords the monohydrate.[5] Structurally, the glutamate anion is zwitterionic, with the amino group protonated (pKa = 9.47) and both carboxylic-acid groups (pKa = 2.10, 4.07) in their deprotonated carboxylate form.[6]

Calcium di-L-glutamate can be used to prepare other glutamates through metathesis with a soluble sulfate, carbonate or hydroxide salt. For example, manganese(II) di-L-glutamate can be prepared through metathesis with manganese(II) sulphate:[7]

Ca(OOC(CH2)2CH(NH3)COO)2 + MnSO4 → Mn(OOC(CH2)2CH(NH3)COO)2 + CaSO4↓

References

  1. P.. Woodward . D. . T.. Shoobridge. Beard . A. . M.. Calcium diglutamate improves taste characteristics of lower-salt soup. Free full text. Ball. Ferrier. European Journal of Clinical Nutrition. 56. 6. 519–523. Jun 2002 . 0954-3007. 12032651. 10.1038/sj.ejcn.1601343.
  2. Kawai . Misako . Sekine-Hayakawa . Yuki . Okiyama . Atsushi . Ninomiya . Yuzo . Gustatory sensation of L- and D-amino acids in humans . Amino Acids . 43 . 6 . 2012 . 0939-4451 . 10.1007/s00726-012-1315-x . 2349–2358.
  3. Schiffman . S . Sennewald . K . Gagnon . J . Comparison of taste qualities and thresholds of D- and L-amino acids . Physiology & Behavior . 27 . 1 . 1981 . 10.1016/0031-9384(81)90298-5 . 51–59.
  4. Web site: First Aid for Chemical and Cleanroom Laboratories . 2009-06-10 . 2009-04-30 . https://web.archive.org/web/20090430024822/http://www.ee.byu.edu/cleanroom/first_aid.phtml . dead .
  5. Sakata . Yoshiki . Horikawa . Toshiyuki . Takenouchi . Kuniharu . Alkaline Earth Salts of Glutamic Acid and Optical Resolution of their Racemic Modifications . Agricultural and Biological Chemistry . 27 . 7 . 1963 . 0002-1369 . 10.1080/00021369.1963.10858140 . 518–525.
  6. Einspahr . H. . Bugg . C. E. . Calcium binding to α-amino acids: the crystal structure of calcium di-L-glutamate tetrahydrate . Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry . 35 . 2 . 1979-02-15 . 10.1107/S0567740879003435 . 316–321.
  7. Devereux . Michael . Jackman . Maura . McCann . Malachy . Casey . Michael . Preparation and catalase-type activity of manganese(II) amino acid complexes . Polyhedron . 17 . 1 . 1998 . 10.1016/S0277-5387(97)00211-8 . 153–158.

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