Sodium metaphosphate, insoluble

CAS 50813-16-6

Listed as an emulsifier, a thickener and an acidity regulator by the US.

Listed as emulsifiers (US) · thickeners (US) · acidity regulators (US) · flavour enhancers (US) · stabilisers (US) · sequestrants (US) · flavouring agents and adjuvants (US) · texturisers (US) · surface-active agents (US)

A high-molecular-weight sodium polyphosphate — two long metaphosphate chains spiralling in opposite directions — used as an emulsifier, sequestrant and texturiser. It is the insoluble member of the metaphosphate family.

Where it is and isn’t permitted

Status of Sodium metaphosphate, insoluble by jurisdiction. Every jurisdiction this site covers is listed, including those where the substance does not appear.
JurisdictionStatusScope and limitsCitation
Australia and New ZealandFood Standards Australia New ZealandPermitted, with conditions

55 food categories

no numerical limit (good manufacturing practice)

Show every food category
  • 0 Preparations of food additives — GMP
  • 1.1.1 Liquid milk (including buttermilk) — GMPOnly UHT goats milk.
  • 1.1.2 Liquid milk products and flavoured liquid milk — GMP
  • 1.2.2 Fermented milk products and rennetted milk products — GMP
  • 1.3 Condensed milk and evaporated milk — GMP
  • 1.4.1 Cream, reduced cream and light cream — GMPOnly UHT creams and creams receiving equivalent or greater heat treatments.
  • 1.4.2 Cream products (flavoured, whipped, thickened, sour cream etc) — GMP
  • 1.5 Dried milk, milk powder, cream powder — GMP
  • 1.6 Cheese and cheese products — GMP
  • 10.2 Liquid egg products — GMP
  • 10.3 Frozen egg products — GMP
  • 10.4 Dried or heat coagulated egg products — GMP
  • 11.1.1 Rainbow sugar — GMP
  • 11.3.1 Dried honey — GMP
  • 11.4 Tabletop sweeteners — GMP
  • 12.1.2 Reduced sodium salt mixture — GMP
  • 12.1.3 Salt substitute — GMP
  • 12.5 Yeast and yeast products — GMP
  • 12.6 Vegetable protein products — GMP
  • 13.3 Formulated meal replacements and formulated supplementary foods — GMP
  • 13.4 Formulated supplementary sports foods — GMP
  • 13.5 Food for special medical purposes — GMP
  • 14.1.1.2 Carbonated, mineralised and soda waters — GMP
  • 14.1.2.1 Fruit and vegetable juices — GMPFor juice separated by other than mechanical means only.
  • 14.1.2.2 Fruit and vegetable juice products — GMP
  • 14.1.3 Water based flavoured drinks — GMP
  • 14.1.4 Formulated Beverages — GMP
  • 14.1.5 Coffee, coffee substitutes, tea, herbal infusions and similar products — GMP
  • 14.2.3 Wine based drinks and reduced alcohol wines — GMP
  • 14.2.4.1 Fruit wine products and vegetable wine products — GMP
  • 14.2.5 Spirits and liqueurs — GMP
  • 14.3 Alcoholic beverages not included in item 14.2 — GMP
  • 2.1 Edible oils essentially free of water — GMP
  • 2.2.1.2 Butter products — GMP
  • 2.2.1.3 Margarine and similar products — GMP
  • 2.2.2 Oil emulsions (<80% oil) — GMP
  • 20 Foods not included in items 0 to 14 — GMP
  • 3 Ice cream and edible ices — GMP
  • 4.1.3 Fruits and vegetables that are peeled, cut, or both peeled and cut — GMP
  • 4.3 Processed fruits and vegetables — GMP
  • 5.1 Chocolate and cocoa products — GMP
  • 5.2 Sugar confectionery — GMP
  • 5.4 Icings and frostings — GMP
  • 6.3 Processed cereal and meal products — GMP
  • 6.4 Flour products (including noodles and pasta) — GMP
  • 7 Breads and bakery products — GMP
  • 8.2 Processed meat, poultry and game products in whole cuts or pieces — GMP
  • 8.3 Processed comminuted meat, poultry and game products, other than products listed in item 8.3.2 — GMP
  • 8.3.2 Sausage and sausage meat containing raw, unprocessed meat — GMP
  • 8.4 Edible casings — GMP
  • 8.5 Animal protein products — GMP
  • 9.1.1 Frozen fish — GMP
  • 9.2 Processed fish and fish products — GMP
  • 9.3 Semi preserved fish and fish products — GMP
  • 9.4 Fully preserved fish including canned fish products — GMP
Food Standards Code, Schedule 15, S15—5and 54 further provisionsretrieved 2026-10-17
CanadaHealth CanadaNo listing matchedHealth Canada’s lists name additives without E or INS numbers, so this site matches them by exact name. A substance listed there under a name this site does not recognise has no row here.
European UnionEuropean Commission / EFSANo listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it.
Great BritainFood Standards Agency / Food Standards ScotlandNo listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it.
JapanConsumer Affairs AgencyNo listing matchedThis site imports only Japan’s list of designated additives (Appended Table 1 to the Regulations for Enforcement of the Food Sanitation Act), matched by English name. Existing additives, natural flavouring agents and ordinary foods used as additives are permitted outside that list and are not imported, so an empty row does not show that Japan does not permit the substance.
South KoreaMinistry of Food and Drug SafetyNo listing matchedThis site imports Part III of South Korea’s Standards and Specifications for Food Additives, matched by CAS number, then INS number, then exact name. Mixed preparations and sanitisers are not imported, and an entry whose identifiers disagreed with a page’s is held for review, so an empty row does not show that South Korea does not permit the substance.
United StatesFood and Drug AdministrationNot listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited.
Codex AlimentariusCodex Alimentarius Commission / JECFANot listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited.

How much is permitted

A listing usually limits the quantity as well as the food. Only one of the forms that takes is a figure: quantum satis and good manufacturing practice permit the amount the technological effect requires and no more, which is a limit rather than the absence of one. Figures below are the range across every food category this page is listed in, and categories differ between regulators — see how much is permitted.

Australia and New Zealand—55 GMP

No regulator sets a figure for Sodium metaphosphate, insoluble. That is not an absence of control: where the listing says quantum satis or good manufacturing practice, the quantity is limited to what the effect requires.

What it is made from

Made by heating sodium phosphate to condense it into long chains, at a sodium-to-phosphate ratio of about one.

  • Vegan
  • Vegetarian

Compare other additives on the dietary indexes.

CAS registry number
50813-16-6

How JECFA defines it

The international specification for identity and purity, prepared by the Joint FAO/WHO Expert Committee on Food Additives and published by FAO. It is a different document from any above, written by a different body and revised on its own cycle; it is advisory, and a country adopts it or does not.

Sodium Metaphosphate, insoluble

A high molecular weight sodium polyphosphate composed of two long metaphosphate chains (NaPO 3 ) x that spiral in opposite directions about a common axis; the Na 2 O/P 2 O 5 ratio is about 1.0; the pH of a 1 in 3 slurry in water is about 6.5.

Synonyms: Insoluble sodium polyphosphate; IMP; Maddrell's salt

Assay, identification and purity criteria

Description and assay

Specification history
Prepared at the 46th JECFA (1996), published in FNP 52 Add 4 (1996). Metals and arsenic specifications revised at the 55th JECFA (2000). A group MTDI of 70 mg/kg bw, as phosphorus from all food sources, was established at the 26th JECFA (1982)
Chemical names
Sodium metaphosphate
C.A.S. number
50813-16-6
Structural formula
where x > = 20
Assay
Not less than 68.7% and not more than 70.0% of P 2 O 5
DESCRIPTION
White crystalline powder
FUNCTIONAL USES
Emulsifier, sequestrant, texturizer
METHOD OF ASSAY
Transfer about 800 mg of the sample, accurately weighed, into a 400-ml beaker. Add 100 ml of water and 25 ml of nitric acid, cover with a watch glass, and boil for 10 min on a hot plate. Rinse any condensate from the watch glass into the beaker; cool the solution to room temperature; transfer it quantitatively to a 500-ml volumetric flask; dilute to volume with water; and mix thoroughly. Pipet 20.0 ml of this solution into a 500-ml Erlenmeyer flask, add 100 ml of water, and heat just to boiling. Add with stirring 50 ml of quimociac TS, then cover with a watch glass, and boil for 1 min in a well-ventilated hood. Cool to room temperature, swirling occasionally while cooling, then filter through a tared, sintered-glass filter crucible of medium porosity, and wash with five 25-ml portions of water. Dry at about 225 o for 30 min, cool, and weigh. Each mg of precipitate thus obtained is equivalent to 32.074 μg of P 2 O 5 .

Identification

Solubility (Vol. 4)
Insoluble in water, soluble in mineral acids and in solutions of potassium and ammonium (but not sodium) chlorides
Gel test
Finely powder about 1 g of the sample, and add slowly to 100 ml of a 1 in 20 solution of potassium chloride while stirring vigorously. A gelatinous mass is formed.
Test for sodium (Vol. 4)
Prepare the test solution by mixing 500 mg of the sample with 10 ml of nitric acid and 50 ml of water. Boil for about 30 min and cool
Test for phosphate (Vol. 4)
Prepare the test solution by mixing 500 mg of the sample with 10 ml of nitric acid and 50 ml of water. Boil for about 30 min and cool

Purity criteria

Fluoride (Vol. 4)
Not more than 10 mg/kg (Method I or III)
Arsenic (Vol. 4)
Not more than 3 mg/kg (Method II)
Lead (Vol. 4)
Not more than 4 mg/kg Determine using an atomic absorption technique appropriate to the specified level. The selection of sample size and method of sample preparation may be based on the principles of the method described in Volume 4, “Instrumental Methods.”

FAO JECFA Monograph 1 (2006)

Every name it appears under

4 recorded names. A label may use any of them.

Other names

  • IMP
  • Insoluble sodium polyphosphate
  • Maddrell's salt
  • Sodium metaphosphate, insoluble

Hazard reference values

No reference value for this substance in the sources we hold.

Evidence and how bodies read it

Studies, and the differing conclusions regulators drew from them, are curated rather than machine-read, and none has been written for this substance yet.

Common questions

Assembled from what is above, in the words the questions are usually asked in. Each answer is the same statement the relevant section makes, with the same citations behind it.

What is Sodium metaphosphate, insoluble?
A high-molecular-weight sodium polyphosphate — two long metaphosphate chains spiralling in opposite directions — used as an emulsifier, sequestrant and texturiser. It is the insoluble member of the metaphosphate family.
What is Sodium metaphosphate, insoluble used for in food?
It is listed as an emulsifier, a thickener and an acidity regulator — the role the US assigns it. This page shows every function each regulator records, with the citation for each.
Where is Sodium metaphosphate, insoluble permitted?
Of the seven regulators this site reads, Australia and New Zealand permits it. Each permission is for named foods at named levels, not a blanket one; the table on this page gives them with citations.
Is Sodium metaphosphate, insoluble vegan?
Yes. Sodium metaphosphate, insoluble is not derived from animals, and is suitable for vegetarians. This page says what it is made from and how.

Sources for this page

  • anz retrieved 2026-10-17
  • jecfaspecs retrieved 2026-09-23

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