Calcium 5'-ribonucleotides

Calcium 5''-ribonucleotides is a mixture of calcium guanylate (calcium GMP) and calcium inosinate (calcium IMP), providing broad-spectrum umami flavour enhancement through the combined action of both nucleotide types. Its name reflects the mixture of two 5''-substituted ribonucleotide calcium salts. By combining GMP and IMP in a single additive, it enables manufacturers to access the synergistic umami effect of nucleotide blending while using a calcium rather than sodium or potassium counter-ion, supporting low-sodium formulations.

JECFA evaluated nucleotide additives in 1987 and assigned a "not specified" ADI to all members of the 5''-ribonucleotide family, consistent with their naturally occurring metabolic roles. Both GMP and IMP are normal cellular metabolites, and calcium is an essential mineral. No toxicological concern arises at food additive concentrations.

Calcium 5''-ribonucleotides is approved in the EU and in other markets as E634. As a mixture of guanylate and inosinate, it carries the same consumer advisory as the individual nucleotide enhancers: it is a purine-containing additive that contributes to uric acid production during metabolism. Individuals managing gout or hyperuricaemia should be aware of E634 alongside E626–E633 when assessing dietary purine load. In practice, this additive appears in savoury snacks, instant noodles, and seasoning blends where the combination of GMP and IMP delivers strong, balanced umami. It is often used in tandem with MSG (E621) to take advantage of the glutamate-nucleotide synergy.