Salt of phosphoric acid. Polyphosphates (sodium polyphosphate, potassium polyphosphate, sodium calcium polyphosphate, calcium polyphosphates) are synthesised derivatives of phosphoric acid (E 338) and are authorised in the EU as food additives under the number E 452. They have different properties and are used in food technology as antioxidants, raising agents, emulsifiers, firming agents, complexing agents, acidity regulators, melting salts, stabilizers and acidity regulators.