CAS No. 7785-84-4 | (NaPO₃)₃ | Molecular Weight 305.89 g/mol

Sodium trimetaphosphate (STMP) is an inorganic cyclic phosphate salt used primarily as a starch crosslinking agent in food processing, and as a chelating, anti-scaling, and surface-treatment agent in industrial formulations.It is a white, odorless, non-flammable powder that dissolves readily in water, making it a practical multifunctional additive across food and technical applications.

What Are the Key Properties of Sodium Trimetaphosphate?

STMP is the sodium salt of trimetaphosphoric acid and exists as a six-membered ring of alternating phosphorus and oxygen atoms.Its cyclic structure is what enables its defining reaction: phosphorylation and crosslinking of starch chains.

Why Is STMP Used in Food Processing?

STMP is valued in the food industry for its ability to modify starches, improve texture, and stabilize processed foods while enhancing moisture retention and preserving color.Its most important food function is as a crosslinking agent in the production of distarch phosphate (E1412), where it links starch chains at a rate of roughly one phosphate bridge per 620 glucopyranose units.This crosslinking raises the starch’s stability to heat, shear, and acid conditions — critical for bakery fillings, convenience foods, and resistant starch ingredients.

Beyond starch modification, food-grade STMP serves as a texturizer and moisture-retention agent in processed meats and seafood, a stabilizer in ice cream and processed cheese, a turbidity preventative in fruit juice drinks, and a phosphorylating agent that protects vitamin C from degradation.It also helps inhibit discoloration in meats, seafood, and juices, preserving visual appeal.

What Does STMP Do in Industrial Applications?

Industrial-grade STMP carries a different value proposition: sequestration and surface activity. It functions as a corrosion inhibitor, anti-scaling agent, chelating agent, and dispersing agent in water treatment, detergents, and cleaning products.It also appears as a finishing agent, plating agent, and surface-treating agent in metal and materials processing.

Emerging uses extend further: STMP has been evaluated as a crosslinker for hyaluronic acid films to improve mechanical strength and stability in pharmaceutical and biomedical applications, and fluoride varnishes containing STMP have been studied for reducing enamel demineralization.

Is Sodium Trimetaphosphate Hazardous to Handle?

STMP is not classified as flammable or explosive, but it is not a dust to ignore. Safety data sheets advise avoiding inhalation of dust and contact with skin and eyes, and note that repeated exposure may cause skin dryness and cracking.Ingestion is harmful and should be avoided.

Practical controls include local exhaust ventilation where dust forms, appropriate PPE (gloves, goggles, dust mask), and storage in a cool, dry, well-ventilated area away from moisture. Food-grade material should be kept under conditions that protect its 36-month shelf life.

What Is the Market Outlook for STMP?

The global sodium trimetaphosphate market was valued at approximately US$48.17millionin2025\ast \ast andisprojectedtoreach\ast \ast US$ 65.71 million by 2032, growing at a CAGR of 4.6%.Global production reached roughly 23,087 metric tons in 2024, at an average market price of around US$ 1,962 per metric ton.Growth is being driven by demand for processed and convenience foods, industrial water treatment, and construction materials, with Asia-Pacific identified as the most dynamic region. Established suppliers include ICL, Innophos, and Xingfa Chemicals.

Frequently Asked Questions

Is sodium trimetaphosphate the same as sodium tripolyphosphate (STPP)?
No. STMP is a cyclic trimetaphosphate with the formula (NaPO₃)₃, while STPP is a linear polyphosphate. Both are used in food and industrial applications, but they differ in reactivity, solubility, and functional behavior.

What is the food additive number for STMP-modified starch?
Starch crosslinked with STMP is typically labelled as distarch phosphate, with the food additive code E1412. STMP itself functions as the crosslinking reagent, not as the finished additive.

Is STMP allowed in organic food?
Food-grade STMP is approved for specific uses under food-contact regulations, including the esterification of food starch with a residual phosphate limit of 0.04% on a phosphorus basis in the modified starch.Organic certification should be verified against the relevant regional standard.