Confused by “phosphorus” vs “phosphate” vs “STPP”? Wondering whether STPP is safe in food,
or which grade to choose for shrimp vs ceramics? This guide gives clear, science-backed answers
— from regulatory status to real-world performance.
CAS: 7758-29-4
Food additive: E451(i)
Typical pH (1%): 9.1–10.1
Core functions: Chelation • Water binding • Protein stabilization
Quick note: “Safe” depends on grade and compliance. Food-grade STPP is produced and tested to meet
strict impurity limits; industrial/technical grades must never be used in food.
Quick Answers
What it is: STPP is an inorganic polyphosphate salt used as a sequestrant and functional ingredient, valued for chelation and water binding.
Food use: Helps maintain juiciness and texture in seafood and improves yield in injected meats.
Industrial use: Detergent builder, ceramic deflocculant, and water-treatment chelant/scale control (case-dependent).
Safety: Food-grade STPP is widely permitted when used according to GMP and local regulations; always verify grade + COA impurity limits.
1) What is STPP? (Chemistry & key properties)
1.1 Definition
Sodium Tripolyphosphate (STPP) — also known as pentasodium triphosphate — is a polyphosphate salt
with the chemical formula Na5P3O10 and CAS number 7758-29-4.
In food applications, it is commonly labeled as E451(i).
1.2 Technical properties (typical)
| Parameter | Typical value / description |
|---|---|
| Appearance | White powder or granules; slightly hygroscopic |
| Solubility | Freely soluble in water; insoluble in ethanol |
| pH (1% solution) | Typically 9.1–10.1 (alkaline) |
| Core functions | Sequestrant (chelating agent), texturizer; supports water binding and protein functionality |
1.3 Phosphorus ≠ Phosphate ≠ STPP (with visual concept map)
Unit reminder: Reports may use “mg P/L” while dosing guides may use “mg PO4/L”.
Conversion: 1 mg P ≈ 3.07 mg PO4.
2) Is STPP safe? (Science, regulations & practical truth)
Safety is inseparable from purity specifications, traceability, and correct grade selection.
2.1 Regulatory snapshot (high-authority references)
| Region / body | What it means | Reference |
|---|---|---|
| United States (FDA) | Recognized as safe when used in accordance with GMP (21 CFR §182.1810). |
21 CFR §182.1810 • FDA “Substances Added to Food” |
| WHO / JECFA | Evaluated by JECFA (tolerable intake expressed as a group MTDI for phosphorus, as P). | WHO JECFA entry |
| European Union | Use is governed by the Union list under Regulation (EC) No 1333/2008 (category-specific conditions). | EC Additives Database |
2.2 “Safe = compliant”: impurity limits (food-grade specs)
Food-grade STPP is tested against strict impurity limits. Typical specification limits include:
| Impurity | Typical limit | Why it matters |
|---|---|---|
| Fluoride (F) | ≤ 50 mg/kg | Purity and intake control |
| Arsenic (As) | ≤ 3 mg/kg | Heavy metal safety control |
| Lead (Pb) | ≤ 4 mg/kg | Heavy metal safety control |
Spec reference:
FAO/JECFA monograph (Pentasodium Triphosphate, PDF)
Industrial-grade STPP must never be used in food.
2.3 Common misconceptions (fast myth-busting)
- “STPP is toxic.” → Food-grade STPP is purified and regulated; the main risk is using non-food grades.
- “It causes cancer.” → Major regulatory evaluations do not support that claim when used within rules and GMP.
- “It’s just a filler.” → It delivers measurable yield/texture/moisture-retention benefits.
3) Where is STPP used? (Food + Industrial panorama)
3.1 Food applications (Food grade STPP / E451(i))
| Application | What STPP does | Typical benefit |
|---|---|---|
| Meat & poultry (injection / tumbling) |
Supports water binding and protein functionality. Mechanism: binds water molecules and chelates metal ions, preventing protein denaturation during freezing/thawing — thus retaining juiciness in shrimp and yield in injected meats. |
Higher yield, better juiciness, improved sliceability |
| Frozen seafood (shrimp / fish) |
Reduces drip loss during thawing; stabilizes texture. Mechanism: chelates pro-oxidant metal ions and helps maintain protein-water interactions, improving bite and moisture retention. |
Firmer bite, less dryness, better consumer perception |
| Dairy (select uses) | Helps stabilize proteins and control interactions | Improved stability and reduced separation (case-dependent) |
| Beverage / processing aids | Chelation and stability support in certain formulations | Reduced haze/precipitation risk (case-dependent) |
3.2 Industrial applications (Industrial grade STPP)
| Industry | Role | Why it’s used |
|---|---|---|
| Detergents & cleaning | Builder / water softener | Binds Ca/Mg ions to improve cleaning and prevent redeposition |
| Ceramics | Deflocculant / dispersant aid | Improves slurry fluidity; reduces water demand and drying energy |
| Water treatment | Scale control / chelation | Helps reduce hardness-driven scaling (case-dependent) |
| Other | Textile, paper, drilling fluids | Process stability and chelation benefits |
Quick Comparison: STPP vs. SHMP vs. TSPP
Below is a technical comparison to help selection.
| Feature | STPP | SHMP | TSPP |
|---|---|---|---|
| Full Name | Sodium Tripolyphosphate | Sodium Hexametaphosphate | Tetrasodium Pyrophosphate |
| pH Value | 9.2 – 10.0 (Alkaline) | 5.8 – 7.3 (Neutral) | 10.0 – 10.8 (High Alkaline) |
| Primary Function | Builder & Chelating Agent | Dispersant & Scale Inhibitor | Buffer & Emulsifier |
| Best Application | Detergents, Ceramics | Water Treatment, Refractory | Toothpaste, Electroplating |
| View Product | Check STPP Price | Check SHMP Price | Check TSPP Price |
4) How to choose the right STPP (Food grade vs Industrial grade)
Always confirm grade, standards, COA impurity limits, and batch traceability.
| Dimension | Food Grade STPP (E451(i)) | Industrial Grade STPP |
|---|---|---|
| Purity focus | Strict impurity controls and traceability | Performance-driven industrial specs |
| Heavy metals & fluoride | Controlled to food-grade limits | Not controlled to food additive limits |
| Typical uses | Meat/seafood, poultry, food processing | Detergents, ceramics, water treatment |
| Packaging | Food-grade inner liner; palletized | Industrial packaging options |
5) Environment & sustainability (what responsible buyers should know)
Goway supports responsible use and offers guidance on wastewater management for industrial clients.
- Implement wastewater phosphorus control (local discharge limits)
- Use the lowest effective dosage for performance targets
- Audit discharge points and document compliance (ESG-ready)
For industrial clients, we can share typical wastewater handling notes and suggest practical monitoring items (case-dependent).
FAQ
Is STPP the same as phosphorus?
No. Phosphorus (P) is an element; phosphate (PO4) is a stable ion; STPP is a polyphosphate salt. Unit conversion matters: 1 mg P ≈ 3.07 mg PO4.
Why is STPP used in shrimp and fish?
Food-grade STPP helps retain moisture during freezing/thawing and supports texture stability, reducing drip loss and dryness.
What’s the difference between STPP and SHMP?
STPP is alkaline and commonly used as a builder/chelating agent; SHMP is closer to neutral and often chosen for dispersion and scale inhibition. Selection depends on your process goals.
Is STPP allowed in the EU and the U.S.?
Yes, with conditions. In the U.S., STPP is recognized as safe under GMP (21 CFR §182.1810). In the EU, use is governed by the Union list under Regulation (EC) No 1333/2008 with category-specific conditions.
Can I use industrial grade STPP in food?
No. Industrial/technical grade STPP must never be used in food. Always use certified food-grade STPP and verify COA impurity limits, traceability, and compliance.
Need certified, high-purity STPP with full traceability?
Goway supplies both Food Grade STPP (E451(i)) and Industrial Grade STPP with document support for audits and quality control.
Request your Technical Data Pack (TDS, COA, SDS) and tell us your application to get a grade recommendation.
- Application (shrimp soak / meat injection / ceramics slurry / detergent)
- Process details (time, temperature, water hardness, target yield/texture)
- Destination market (US / EU / SEA)
- Packaging needs (25 kg / 1000 kg; palletized; inner liner)
Compliance note: Final usage levels and labeling depend on local regulations, product category, and GMP. Always validate with your QA/regulatory team.
Related reading:
Is Sodium Tripolyphosphate (STPP) Safe? •
Is Phosphate the Same as Phosphorus?
