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. Notably, only the L isomer is used in flavouring as D-glutamate does not have an umami/savoury flavour.
As a soluble source of calcium ions, this chemical is also used as a first-aid treatment for exposure to hydrofluoric acid.
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.6 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.7
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:8
Ca(OOC(CH2)2CH(NH3)COO)2 + MnSO4 → Mn(OOC(CH2)2CH(NH3)COO)2 + CaSO4↓References
Ball, P.; Woodward, D.; Beard, T.; Shoobridge, A.; Ferrier, M. (Jun 2002). "Calcium diglutamate improves taste characteristics of lower-salt soup". European Journal of Clinical Nutrition (Free full text). 56 (6): 519–523. doi:10.1038/sj.ejcn.1601343. ISSN 0954-3007. PMID 12032651. /wiki/Doi_(identifier) ↩
Kawai, Misako; Sekine-Hayakawa, Yuki; Okiyama, Atsushi; Ninomiya, Yuzo (2012). "Gustatory sensation of L- and D-amino acids in humans". Amino Acids. 43 (6): 2349–2358. doi:10.1007/s00726-012-1315-x. ISSN 0939-4451. PMID 22588481. /wiki/Doi_(identifier) ↩
Schiffman, S; Sennewald, K; Gagnon, J (1981). "Comparison of taste qualities and thresholds of D- and L-amino acids". Physiology & Behavior. 27 (1): 51–59. doi:10.1016/0031-9384(81)90298-5. PMID 7267802. /wiki/Doi_(identifier) ↩
"First Aid for Chemical and Cleanroom Laboratories". Archived from the original on 2009-04-30. Retrieved 2009-06-10. https://web.archive.org/web/20090430024822/http://www.ee.byu.edu/cleanroom/first_aid.phtml ↩
Sakata, Yoshiki; Horikawa, Toshiyuki; Takenouchi, Kuniharu (1963). "Alkaline Earth Salts of Glutamic Acid and Optical Resolution of their Racemic Modifications". Agricultural and Biological Chemistry. 27 (7): 518–525. doi:10.1080/00021369.1963.10858140. ISSN 0002-1369. /wiki/Doi_(identifier) ↩
Sakata, Yoshiki; Horikawa, Toshiyuki; Takenouchi, Kuniharu (1963). "Alkaline Earth Salts of Glutamic Acid and Optical Resolution of their Racemic Modifications". Agricultural and Biological Chemistry. 27 (7): 518–525. doi:10.1080/00021369.1963.10858140. ISSN 0002-1369. /wiki/Doi_(identifier) ↩
Einspahr, H.; Bugg, C. E. (1979-02-15). "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): 316–321. doi:10.1107/S0567740879003435. /wiki/Doi_(identifier) ↩
Devereux, Michael; Jackman, Maura; McCann, Malachy; Casey, Michael (1998). "Preparation and catalase-type activity of manganese(II) amino acid complexes". Polyhedron. 17 (1): 153–158. doi:10.1016/S0277-5387(97)00211-8. /wiki/Doi_(identifier) ↩