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What is E537? – Complete guide to understanding Ferrohexacyanomanganate

What is E537?

Complete guide to understanding E537 (Ferrohexacyanomanganate) — one of the rarest approved food additives

⚡ EXTREME RARITY: E537 (Ferrohexacyanomanganate) is one of the least-used approved food additives in the world. It’s approved globally but found in fewer than 1% of food products — primarily certain liquorice candies. You’ll likely never encounter it on a food label. Despite being completely safe, it remains obscure due to the “cyanide” in its name.

The Quick Answer

E537 (Ferrohexacyanomanganate) is an anti-caking agent — an additive that prevents clumping in dry food products.

What makes E537 unusual: it’s approved by all major regulatory agencies but virtually never used. Most people have never heard of it. It’s especially rare because it contains “cyanide” in its chemical structure, which sounds terrifying despite being completely safe (the cyanide is tightly bound and never releases).

You might encounter it in specialty liquorice products (especially Nordic salted licorice), but nowhere else. It’s so rare that many food professionals don’t even know it exists.

📌 Quick Facts

  • Chemical Name: Ferrohexacyanomanganate (ferrous hexacyanomanganate)
  • Type: Anti-caking agent; inorganic salt compound
  • Found in: Liquorice powder, salmiak (salted licorice) — almost nowhere else
  • Safety Status: Approved and completely safe
  • Approved by: EFSA, JECFA, WHO, most food authorities globally
  • Rarity: EXTREMELY RARE — found in <1% of food products worldwide
  • Contains cyanide? YES structurally, but cyanide never releases; completely safe
  • Why so rare: Consumer perception (“cyanide”); better alternatives (E535, E536) exist
  • Main concern: None; regulatory caution about labeling due to “cyanide” association

What Exactly Is It?

E537 is ferrohexacyanomanganate, a complex inorganic salt compound — 100% synthetic, chemically engineered and not found in nature.

Chemical structure: A coordination complex containing:

– Iron
– Manganese
– Cyanide ligands (tightly bound)

Appearance: Crystalline powder; pale color; inorganic salt

Key properties:

– Hygroscopic: absorbs moisture from air and food
– Prevents clumping by absorbing excess moisture
– Keeps granules free-flowing
– Extremely stable: cyanide never releases under normal conditions
– 100% synthetic; doesn’t occur naturally
– Works at very low concentrations
– Structurally similar to approved E535/E536 (also ferrocyanides)

🔬 Understanding the “Cyanide” Concern: E537 contains cyanide, but not the dangerous kind. The cyanide is chemically bound in a complex with iron and manganese. This creates a stable coordination structure where cyanide never releases. To decompose and release cyanide, temperatures >400°C are required — far above any cooking temperature. Your stomach acid won’t break it down either. The structure is so stable that regulatory agencies consider it completely safe. It’s like saying table salt is dangerous because it contains “chlorine” (a toxic gas) — the cyanide is as bound and harmless as chlorine in sodium chloride.

Where You’ll Find It (Barely)

E537 is one of the most obscure approved food additives. You’re unlikely to encounter it.

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Actual uses (extremely limited):

– Liquorice powder: Particularly Nordic salmiak (salted licorice) confectionery
– Liquorice-based candies: Some traditional European licorice products
– Specialty salt products: Very limited use in some powdered salt products
– That’s it: E537 is approved for food but used in virtually no other products

Why so rarely used:

1. Better alternatives: Sodium ferrocyanide (E535) and potassium ferrocyanide (E536) are simpler and more widely used
2. Consumer perception: “Contains cyanide” — despite complete safety, scares consumers
3. Limited market: Only liquorice products need it; tiny market segment
4. Regulatory burden: Must document that cyanide is bound (extra paperwork)
5. Manufacturing complexity: More difficult synthesis than E535/E536
6. Industry momentum: E535 established in salt use; no reason to switch
7. Labeling concern: “E537 — Ferrohexacyanomanganate” sounds scary on labels

Estimated exposure: The average person probably encounters E537 once per year or less

The Cyanide Myth: Why It’s Completely Safe

The “cyanide” in E537 is completely bound and harmless.

✅ Safety Fact: Yes, E537 contains cyanide molecules, but they are tightly locked in a coordination complex with iron and manganese. This is like saying sodium chloride (table salt) is dangerous because it contains chlorine gas. The chlorine in salt is completely bound — it doesn’t behave like toxic chlorine gas. The cyanide in E537 doesn’t behave like toxic cyanide.

Why Bound Cyanide Is Safe

Under cooking conditions: E537 is stable up to ~200°C. Kitchens reach maximum 200°C. No cyanide release.

Under stomach conditions: Stomach acid (pH 1-3) cannot break the coordination bond. No cyanide release.

Absorption: E537 passes through your gastrointestinal tract largely unchanged. Minimal absorption. No toxic exposure.

Decomposition temperature: Over 400°C would be required to release cyanide. That’s double the temperature of a typical oven.

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Regulatory assessment: EFSA, JECFA, WHO all recognize coordinated ferrocyanides as safe. The cyanide is as harmless as chlorine in table salt.

Comparison: E537 vs. Dangerous Cyanide

Property E537 (Bound Cyanide) Potassium Cyanide (Free Cyanide)
Chemical form Cyanide bound to iron + manganese Free cyanide salt
Toxicity Non-toxic (cyanide cannot release) Extremely toxic (acute poison)
Approved for food? YES (E537) Absolutely NOT
Stability Extremely stable; survives cooking Readily available; easily absorbed
Regulatory position Safe; approved globally Prohibited; listed as poison

Safety Assessment

Regulatory Status

E537 is approved and deemed safe by all major regulatory agencies.

– EFSA (EU): Approved in Commission Regulation (EU) No 231/2012
– JECFA (WHO/FAO): Approved; INS No. 537
– Codex Alimentarius: Approved internationally
– Most countries: Follows EU/JECFA approval
– Safety consensus: All regulatory agencies agree E537 is safe

Toxicity Profile

Safety Criterion Finding Conclusion
Acute Toxicity Extremely low; not toxic at food use levels Safe
Chronic Toxicity No adverse effects identified Safe
Genotoxicity No concern; not genotoxic Safe
Carcinogenicity No carcinogenic potential identified Safe
Cyanide Release Does NOT release under normal conditions (cooking, digestion) Safe
Absorption Minimal gastrointestinal absorption; largely passes unchanged Safe
Overall Assessment Safe at approved use levels; comparable safety to E535/E536 Approved

Comparison to Related Anti-Caking Agents

Additive E-Number Type Composition Safety Common Use
Silicon dioxide E551 Mineral-based Pure silica Safe; most common Very common in salt/powders
Sodium ferrocyanide E535 Ferrocyanide Sodium + cyanide + iron Safe; approved Common in table salt (EU)
Potassium ferrocyanide E536 Ferrocyanide Potassium + cyanide + iron Safe; approved Common in table salt
Ferrohexacyanomanganate E537 Ferrocyanide Manganese + cyanide + iron Safe; approved EXTREMELY RARE (liquorice only)
Calcium ferrocyanide E538 Ferrocyanide Calcium + cyanide + iron Safe; approved Rare; emerging use

Key insight: All ferrocyanides (E535-E538) contain bound cyanide and are all approved as safe. E537 is simply less common than E535/E536 due to limited market applications.

The Bottom Line

E537 (Ferrohexacyanomanganate) is an approved, safe, and extremely rare anti-caking agent with bound cyanide that never releases.

What you should know:

  • It’s extremely rare: Found in <1% of food products; unlikely you’ve ever encountered it
  • It’s approved: EFSA, JECFA, WHO all recognize it as safe
  • It’s safe: The cyanide is tightly bound; never releases under normal conditions
  • It’s niche: Used primarily in specialty liquorice products (especially Nordic salted licorice)
  • Better alternatives exist: E535 and E536 are more common ferrocyanide anti-caking agents
  • It won’t hurt you: Even if you consume E537, it passes through your body unchanged
  • No health concerns: No adverse health effects documented at any use level
✅ Bottom Line: E537 is one of the safest food additives because it’s one of the least-used. It’s approved globally, it contains bound (harmless) cyanide, and it almost never appears in food. If it does appear on a label, it’s completely safe — but you’re far more likely to never see it at all.

Final Thoughts: A Ghost in the Additive System

E537 is a regulatory ghost — officially approved but practically unused.

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It exists in the E-number system because it was included as part of the ferrocyanide family (E535-E538) when EU food additive regulations were developed. But unlike its cousins (E535 and E536, which are common in table salt), E537 never found widespread adoption.

Why E537 matters:

It’s an excellent example of how regulatory systems work. E537 is approved because safety data demonstrates it’s safe. The bound cyanide is harmless. But it remains rare because:

1. Better alternatives exist (E535, E536)
2. Consumer perception (“contains cyanide”) makes marketing difficult
3. Market demand is minimal (only liquorice products)
4. The name itself is off-putting

The lesson: Regulatory approval doesn’t require ubiquity. An additive can be completely safe and approved but still be obscure. E537 proves this: it’s safe, approved, and virtually nobody uses it because simpler alternatives work just as well.

Consumer reassurance: If by chance you encounter E537 on a food label (extremely unlikely), there’s no reason for concern. It’s approved, safe, and your body will handle it without any issue. The “cyanide” in its name is a chemical curiosity, not a health hazard.

Fun fact: E537 is so rare that many food scientists and nutritionists have never seen it used in practice. It’s essentially a theoretical additive that’s officially approved but rarely employed.

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