E451I - Pentasodium triphosphate

At a glance

• Also known as E451i, sodium tripolyphosphate, STPP
• Roles: emulsifier, stabiliser, humectant (keeps moisture), sequestrant (binds metal ions), thickener
• Common in: brines and marinades for processed meat and poultry; some ready-to-eat and plant-based foods
• Chemistry: a sodium phosphate built from three phosphate units (a “polyphosphate”)
• Made by neutralising phosphoric acid and then heating to link phosphate units
• Nutrition notes: adds phosphorus and sodium; regulated use levels apply
• Regulatory status: permitted in the EU and U.S. within set limits

Why is Pentasodium triphosphate added to food?

Food makers use STPP to bind metal ions (sequestration), control pH, and keep proteins from toughening. This helps meat and poultry hold water, stay tender, and keep a uniform bite.¹ Chemically, it is the sodium salt of triphosphoric acid with the formula Na5P3O10, part of the broader family of phosphate and polyphosphate additives.²

In meat and poultry processing, STPP is valued for improving water-holding capacity during tumbling, injection, or brining, which supports juiciness after cooking.³ It also stabilises emulsions and textures in mixed products, reducing separation and syneresis (water weeping).

What foods contain Pentasodium triphosphate?

You’ll most often find STPP in:

• Processed meats and poultry, such as injected hams, deli meats, marinated chicken, and formed meat products (where phosphates are specifically allowed within limits)³
• Some chilled or frozen prepared foods, sauces, and analog products where moisture retention or texture stability is needed
• A few beverages or dairy-style formulations where phosphate buffering is helpful

Always check the ingredient list for “pentasodium triphosphate,” “sodium tripolyphosphate,” or “E451i.”

What can replace Pentasodium triphosphate?

Depending on the job you need done, these can be alternatives:

• For buffering or mineral action: sodium phosphates, diphosphates, or potassium phosphates to reduce sodium
• For moisture or texture: carrageenan, xanthan gum, or guar gum
• For pH adjustment: sodium bicarbonate, sodium citrates, glucono delta-lactone, or lactic acid

The best swap depends on the food and the exact function (water binding, emulsifying, or pH control).

How is Pentasodium triphosphate made?

STPP is produced by neutralising phosphoric acid with sodium sources such as sodium carbonate or sodium hydroxide, then heating (condensing) the salts to link phosphate units and form sodium tripolyphosphate.¹ The result is usually a white, granular or powder product that dissolves in water.²

Is Pentasodium triphosphate safe to eat?

Regulators have set clear rules for phosphate additives. In the EU, EFSA established a group acceptable daily intake (ADI) of 40 mg/kg body weight per day, expressed as phosphorus, for phosphates including E451.¹ In the U.S., USDA/FSIS allows the use of phosphates in meat and poultry with limits typically not exceeding 0.5% in the finished product (calculated as P2O5).³ The U.S. FDA also lists sodium tripolyphosphate on its Food Additive Status List, indicating permitted uses under regulations and good manufacturing practice.⁴

As with any additive, real-world intake depends on how much processed food you eat. If you follow a balanced diet with a mix of fresh and minimally processed foods, exposure is usually well below regulatory limits.

Does Pentasodium triphosphate have any benefits?

• Food quality: Helps meat and poultry retain moisture and tenderness, supports stable textures, and improves freeze–thaw performance.
• Processing: Buffers pH and binds metal ions, which can help protect color, flavor, and stability in complex recipes.
• Nutrition context: It supplies phosphorus, an essential mineral, but additives are not meant as nutrient supplements; whole foods remain the primary source.

Who should avoid Pentasodium triphosphate?

• People with chronic kidney disease (CKD) or those told to limit phosphorus should watch intake of phosphate additives, including E451, because impaired kidneys may not clear extra phosphorus well.⁵
• Anyone on a physician-advised low-sodium or low-phosphate diet should read labels and choose suitable alternatives.

If you have a medical condition, ask your healthcare provider or dietitian for tailored advice.

Myths & facts

• Myth: “STPP is only a detergent chemical.” Fact: It is also a regulated food additive used for specific, well-defined functions.
• Myth: “All phosphates are the same.” Fact: There are many phosphate additives (mono-, di-, tri-, and polyphosphates), each with different strengths in foods.
• Myth: “It’s unregulated.” Fact: Both the EU and U.S. regulate phosphates, set use limits, and review safety.¹³
• Myth: “It always means added water.” Fact: STPP can help foods hold their natural moisture, but labeling rules still apply and vary by product type.

Pentasodium triphosphate in branded foods

You’ll see E451i on labels of:

• Marinated or injected meats and poultry (e.g., deli turkey, cured ham, seasoned chicken)
• Formed or restructured meat items (e.g., nuggets, patties)
• Some prepared or frozen meals where stable texture and moisture are important

To check, read the ingredient list for “pentasodium triphosphate,” “sodium tripolyphosphate,” or “E451i.”

References

Footnotes

1. Re-evaluation of phosphoric acid–phosphates–di-, tri- and polyphosphates (E 338–E 452) as food additives — EFSA Journal (2019). https://www.efsa.europa.eu/en/efsajournal/pub/5674 ↩ ↩² ↩³ ↩⁴

2. Sodium tripolyphosphate — PubChem (NIH). https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-tripolyphosphate ↩ ↩²

3. 9 CFR § 424.21 — Use of food ingredients and sources of radiation — eCFR (USDA/FSIS). https://www.ecfr.gov/current/title-9/chapter-III/subchapter-E/part-424/section-424.21 ↩ ↩² ↩³ ↩⁴

4. Food Additive Status List — U.S. Food and Drug Administration (FDA). https://www.fda.gov/food/food-additives-petitions/food-additive-status-list ↩

5. Phosphorus: Tips for People with Chronic Kidney Disease — National Institute of Diabetes and Digestive and Kidney Diseases (NIH). https://www.niddk.nih.gov/health-information/kidney-disease/ckd-diet-kidney-disease/phosphorus ↩