What is E539?

Complete guide to understanding E539 (Sodium Thiosulfate) — a specialized antioxidant for preventing browning in potato products

🥔 SPECIALTY ADDITIVE FOR POTATOES: E539 (Sodium Thiosulfate) is a specialized antioxidant used primarily to prevent enzymatic browning in potato products. It’s approved and safe, but has limited applications compared to general-purpose additives. Most consumers never encounter E539 on labels because it’s often used as a processing aid that may not require labeling. It’s a well-studied, pharmacologically approved compound with established safety.

The Quick Answer

E539 (Sodium Thiosulfate) is an antioxidant used to prevent browning in potato products — and it’s completely safe.

What makes E539 unique: It’s a specialized additive approved specifically for potatoes and potato-based products to prevent both enzymatic browning (darkening from enzyme activity) and non-enzymatic browning (from the Maillard reaction). Unlike many food additives, sodium thiosulfate is also used medically and has FDA approval for treating cisplatin-induced hearing loss in cancer patients, which demonstrates its thorough safety evaluation. E539 is effective, safe, and approved globally.

E539 is safe, well-studied, and one of the most specialized food additives.

📌 Quick Facts

Chemical Name: Sodium Thiosulfate; Sodium Thiosulphate
Type: Antioxidant; food additive; inorganic compound
Chemical formula: Na₂S₂O₃·5H₂O (pentahydrate)
Found in: Potato products (primary approved use)
Primary function: Prevents browning; preserves color in potatoes
Safety Status: Approved and completely safe
Approved by: EU, FDA, JECFA, FSSAI (India); most countries
ADI (JECFA): 0.0-0.7 mg/kg body weight/day (since 1985)
Medical approval: FDA approved 2022 (Pedmark) for cisplatin toxicity
Rarity: Specialized additive; limited applications; often unlabeled

What Exactly Is It?

E539 is sodium thiosulfate, a white crystalline compound that acts as a reducing agent and antioxidant — 100% synthetic, chemically manufactured.

Chemical structure: Na₂S₂O₃ (sodium salt of thiosulfate ion, S₂O₃²⁻)

Appearance: White or colorless crystals; dissolves easily in water; odorless

Key properties:

– Antioxidant: prevents browning through reduction reactions
– Reducing agent: donates electrons; scavenges oxygen and free radicals
– Inhibits enzymes: reduces polyphenol oxidase activity
– Water-soluble: dissolves readily for application
– Stable: doesn’t react with other food ingredients
– Non-toxic at food use levels: well-studied safety profile
– Pharmacologically approved: FDA-approved medical use confirms safety
– Effective: works at low concentrations

🔬 Understanding E539’s Anti-Browning Action: E539 prevents browning through multiple mechanisms. Enzymatic browning occurs when the enzyme polyphenol oxidase (PPO) oxidizes polyphenols to brown polymers. Sodium thiosulfate reduces these brown compounds back to colorless forms and inhibits PPO activity. Additionally, E539 prevents non-enzymatic browning (Maillard reaction) by reducing free oxygen and preventing oxidative degradation. This makes it particularly effective for potato products that would otherwise brown during processing, storage, and freezing.

Where You’ll Find E539

E539 is used almost exclusively in potato and potato-based products to prevent browning.

Product	Use	Frequency	Notes
Fresh potatoes (whole)	Anti-browning dip solution	Moderate	Applied to prevent cut-surface browning
Frozen potatoes	Anti-browning during processing	Common	French fries, hash browns, etc.
Dehydrated potatoes	Anti-browning; color preservation	Moderate	Instant mashed potato, flakes
Potato starch	Color preservation during extraction	Limited	Processing aid; may not appear on label
Other foods	Not approved for general use	N/A	Limited to potato products (EU)

Important note: E539 is often used as a processing aid and may not appear on ingredient labels depending on jurisdiction. Potato products may contain E539 without it being explicitly listed.

Is E539 Safe? Absolutely

FDA Medical Approval: Ultimate Safety Confirmation

The strongest evidence of E539’s safety is FDA medical approval:

In September 2022, the FDA approved sodium thiosulfate (trade name Pedmark) for pediatric cancer patients receiving cisplatin chemotherapy to reduce hearing loss. This represents rigorous clinical evaluation including:

– Two large multicenter randomized controlled trials (SIOPEL 6: 114 patients; COG ACCL0431: 125 patients)
– Efficacy demonstrated: 44% hearing loss rate with thiosulfate vs. 58% without
– Safety monitoring: extensive adverse event tracking
– Pediatric use: indicates very careful safety evaluation for vulnerable population
– Ongoing medical monitoring: continuous post-approval surveillance

This FDA approval is significant because it means sodium thiosulfate has undergone far more rigorous safety testing than most food additives.

Food Safety Assessment

Safety Criterion	Finding	Conclusion
ADI (Acceptable Daily Intake)	0.0-0.7 mg/kg body weight/day (JECFA 1985; still current)	Safe
Acute toxicity	Very low; oral LD₅₀ >2000 mg/kg in rats	Safe
Chronic toxicity	No adverse effects at permitted food use levels	Safe
Genotoxicity	No concern identified	Safe
Carcinogenicity	No evidence of cancer in animal studies	Safe
Gastrointestinal absorption	Poorly absorbed; mostly excreted unchanged	Safe
Bioaccumulation	No accumulation in tissues	Safe
Medical use safety	FDA-approved 2022; clinical trials demonstrate safety; pediatric use approved	Very Safe

Actual Consumption vs. Safety Limit

Real exposure calculation for potato consumers:

Typical use level in potatoes: 200-1000 mg/kg

Average potato consumption: 50-200 g/day (varies by region)

E539 intake at typical levels: ~10-200 μg/day (0.00001-0.0002 mg/day)

JECFA ADI for 70 kg adult: 49 mg/day

Safety margin: 100,000x between typical consumption and ADI limit

Even for heavy potato consumers (500 g/day): Would ingest ~0.5 mg E539/day, still 100x below ADI

✅ Safety Reassurance: E539 is completely safe. It’s approved by all major regulatory authorities. JECFA’s ADI has been stable since 1985, reflecting confidence in safety. Most importantly, the FDA approved sodium thiosulfate in 2022 for pediatric cancer patients, demonstrating thorough safety evaluation at medical doses far exceeding food use levels. You have a 100,000x safety margin between consumption and the ADI limit.

The Bottom Line

E539 (Sodium Thiosulfate) is a completely safe specialized antioxidant used to prevent browning in potato products.

What you should know:

It’s safe: Approved globally; JECFA ADI since 1985
It’s medically approved: FDA approval for cisplatin toxicity (2022) demonstrates thorough safety evaluation
It’s specialized: Primarily for potato products; limited approved applications
It’s effective: Works at low concentrations to prevent browning
It’s often unlabeled: May be used as processing aid; not required on every label
You have huge safety margin: 100,000x between consumption and ADI
It’s poorly absorbed: Mostly passes through unchanged; excreted
No health concerns: Safe at all realistic consumption levels

✅ Bottom Line: E539 is one of the safest food additives, particularly because it’s not only approved as a food additive but also approved by the FDA as a pharmaceutical (Pedmark) for pediatric cancer patients. This dual approval demonstrates exceptional safety standards. It’s a specialized additive that most consumers don’t notice, but when encountered, it’s completely harmless.

Final Thoughts: Dual Approval as Food and Medicine

E539 is unusual among food additives because it has dual regulatory approval: both as a food additive AND as an FDA-approved pharmaceutical.

In 2022, the FDA approved sodium thiosulfate (Pedmark) for pediatric cancer patients receiving cisplatin chemotherapy. This represents:

– Two large clinical trials (239+ patients)
– Rigorous safety monitoring
– Approval for vulnerable population (pediatric patients)
– Doses that can be much higher than food use
– Ongoing post-approval surveillance

This pharmaceutical approval provides exceptional confidence in E539’s safety as a food additive because food doses are negligible compared to medical doses.

Comparison to other additives: Most food additives are evaluated ONLY as food additives. E539 has been evaluated both as food and medicine, providing double confirmation of safety.

Why E539 isn’t more common despite safety:

1. Narrow approved applications (potatoes only in many jurisdictions)
2. Better alternatives for other purposes (ascorbic acid/Vitamin C is more versatile)
3. Often used as processing aid (doesn’t require labeling)
4. Market preference for “natural” alternatives in potato products
5. Specialty ingredient with limited distribution

Consumer takeaway: If you see E539 on a potato product label, you can be extremely confident it’s safe. It’s been approved for food use since at least the 1970s and approved by the FDA for pediatric medical use in 2022. It’s arguably one of the most thoroughly evaluated food additives globally.

The bigger picture: E539 exemplifies how modern food safety systems work — substances are evaluated rigorously before approval, re-evaluated periodically, and often have multiple layers of approval (food + medical). When a substance is approved for both food AND pediatric medical use, consumers can have exceptional confidence in its safety profile.

What is E539? – Complete guide to understanding Sodium Thiosulfate