E633 - Calcium inosinate

At a glance

• What it is: the calcium salt of IMP (a nucleotide), used as a flavor enhancer (umami booster)
• Where it’s used: soups, bouillon, instant noodles, snacks, sauces, and seasoning mixes
• How it works: strengthens savory notes and works synergistically with glutamate (for example, MSG)
• Regulatory status: authorized as a food additive in the EU with defined specifications
• Typical amount: very small, often under good manufacturing practice levels
• Label names: “calcium inosinate,” “E633,” or “INS 633”

Why is Calcium inosinate added to food?

It is added to heighten savory, meaty, or brothy flavors. Calcium inosinate belongs to the 5′-ribonucleotide enhancers and shows strong synergy with glutamate (such as monosodium glutamate), which makes foods taste fuller with very small amounts of the additive.¹ It is classified and used as a flavor enhancer in international and EU systems.²³

What foods contain Calcium inosinate?

You’ll most often find E633 in savory products such as soups and bouillons, seasoning blends, snack foods, instant noodles, sauces, and ready meals. Its use in these kinds of foods is recognized in the Codex General Standard for Food Additives (GSFA), where it is listed as a flavor enhancer (INS 633).² In the EU, it is an authorized food additive within the flavor enhancer class, subject to conditions in the food categories where it is allowed.³

What can replace Calcium inosinate?

• Other inosinate salts, such as disodium inosinate or inosinic acid (the free acid form), can serve a similar role.
• Guanylate-based enhancers like disodium guanylate or the blend disodium 5‑ribonucleotide are common alternatives with a comparable umami effect.
• These enhancers are often used together with monosodium glutamate or natural glutamate sources to achieve strong savory taste while keeping usage levels low.¹

How is Calcium inosinate made?

Manufacturers produce IMP (inosine 5′-monophosphate) by microbial fermentation or by enzymatic processing of nucleotide-rich materials. The IMP is then converted to its calcium salt by neutralizing the acid form with a calcium source to yield calcium inosinate.¹⁴ The EU lays down identity and purity specifications for E633, ensuring consistent composition and quality across producers.⁴

Is Calcium inosinate safe to eat?

Within the EU, calcium inosinate is authorized as a food additive and has official specifications under Regulation (EU) No 231/2012, which supports its safety when used as intended.⁴ EFSA (the European Food Safety Authority) has evaluated closely related 5′‑ribonucleotide flavor enhancers and did not identify safety concerns at reported use levels.¹ Many applications use it under “good manufacturing practice,” meaning only the minimum amount needed to achieve flavor is added.²

Does Calcium inosinate have any benefits?

• Taste: It significantly boosts savory flavors and works especially well in combination with glutamate, helping seasonings taste richer.¹
• Formulation: Because it is potent, food makers can use very small amounts to reach the desired flavor impact.²

Calcium inosinate is not added for nutrition, and the calcium contribution from typical use levels is negligible.

Who should avoid Calcium inosinate?

Most people can consume products containing E633 as part of a normal diet. If you are following a specialized diet that limits added nucleotides (for example, under medical advice), talk with a health professional about whether products with ribonucleotide flavor enhancers are appropriate for you. Parents and caregivers should follow the specific rules and guidance that apply to foods for infants and young children, which are regulated separately in many regions.³

Myths & facts

• “It’s the same as MSG.” False. Calcium inosinate is not MSG; it’s a ribonucleotide. However, it often works together with glutamate to strengthen umami.¹
• “It’s used in large amounts.” False. It is effective at very low levels and is often used under good manufacturing practice conditions.²
• “It always comes from animal sources.” Mostly false today. Modern manufacturing commonly uses microbial fermentation or enzymatic processes; check with the manufacturer if source matters to you.¹

Calcium inosinate in branded foods

On labels, look for “calcium inosinate,” “E633,” or “INS 633.” You’ll commonly see it on savory snacks, seasoning packets for instant noodles, bouillon cubes and pastes, jarred or powdered sauces, and ready-to-eat soups. It often appears alongside other enhancers like disodium inosinate, disodium guanylate, or monosodium glutamate.

References

Footnotes

1. Re-evaluation of ribonucleotides (E 627, E 631, E 635) as food additives — EFSA Journal 2017;15(4):4742. https://www.efsa.europa.eu/en/efsajournal/pub/4742 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

2. Calcium 5′-inosinate (INS 633) — Codex GSFA Online (FAO/WHO). https://www.fao.org/gsfaonline/additives/details.html?ins=633 ↩ ↩² ↩³ ↩⁴ ↩⁵

3. Regulation (EC) No 1333/2008 on food additives — EUR-Lex. https://eur-lex.europa.eu/eli/reg/2008/1333/oj ↩ ↩² ↩³

4. Commission Regulation (EU) No 231/2012 laying down specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008 — EUR-Lex. https://eur-lex.europa.eu/eli/reg/2012/231/oj ↩ ↩² ↩³