Potassium Phosphate, identified by the code E340 as a food additive, is an inorganic chemical compound composed of potassium and phosphoric acid. It is primarily used as an acidity regulator, emulsifier, and stabilizer in food products. It is available in various forms, including monopotassium, dipotassium, and tripotassium phosphate, each with specific chemical properties and applications. Potassium phosphate is commonly found in processed foods such as beverages, powdered products, and baked goods, where it plays an important role in maintaining pH balance and stabilizing emulsions.

Chemical Composition and Structure

Potassium phosphate exists in different forms:

• Monopotassium phosphate (KH₂PO₄)
• Dipotassium phosphate (K₂HPO₄)
• Tripotassium phosphate (K₃PO₄)

These variations result from the number of hydrogen atoms replaced by potassium atoms in the phosphoric acid structure. Their chemical formulas reflect their ability to neutralize acids, making these variants useful in different food and industrial contexts.

Physical Properties

Potassium phosphate is a white crystalline solid, odorless, and water-soluble. It has pH-regulating properties, making it useful for balancing acidity in food products. In both liquid and powder form, it is easily mixable with other food ingredients, facilitating the stabilization of formulations.

Production Process

Potassium phosphate is typically produced by reacting phosphoric acid with potassium hydroxide or potassium carbonate. This chemical reaction yields the different forms of potassium phosphate, which can be purified and crystallized for use in food or other applications. 

• Selection of Raw Materials: The main ingredients for producing potassium phosphate include phosphoric acid and potassium hydroxide. These chemical compounds are readily available and chosen for their purity and quality.

• Neutralization Reaction: Phosphoric acid is mixed with potassium hydroxide in a chemical reactor. This reaction occurs under controlled temperature and pH conditions, where the acid and base neutralize to form potassium phosphate. 

• Crystallization: After the reaction, the solution containing potassium phosphate is cooled to allow the product to crystallize. The crystals of potassium phosphate are then collected.

• Purification: The obtained potassium phosphate crystals are purified to remove any impurities and residues. This may include washing and filtration processes to ensure a high-quality product.

• Quality Control and Packaging: Finally, potassium phosphate undergoes quality control checks to verify its purity and functional properties. After analysis, it is packaged for distribution and use in food and cosmetic products.

Food

In the food industry, it is used as an acidity regulator and to prevent the formation of lumps in baked goods.

An ingredient included in the list of European food additives as E340 acidity regulator and chelating agent with the following specifications :

• E340 (i) Monopotassium phosphate   CAS   7778-77-0
• E340 (ii) Dipotassium phosphate   CAS   7758-11-4 
• E340 (iii) Tripotassium phosphate   CAS   7778-53-2 

Medical

Potassium phosphate is widely used to control hypophosphatemia, i.e. phosphate deficiency in the blood, and to prevent the formation of kidney stones.

Cosmetics

Antibacterial and to prevent the formation of lumps.

Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.

Other uses

As an industrial product, it is made from phosphoric acid and has numerous applications in various sectors:

• agricultural fertilisers
• forestry
• fishing

Safety

The Panel on Food Additives and Flavourings added to Food (FAF) provided a scientific opinion re-evaluating the safety of phosphates (E 338–341, E 343, E 450–452) as food additives. The Panel considered that (1). The Panel considered that phosphates have low acute oral toxicity and there is no concern regarding genotoxicity and carcinogenicity. The Panel calculated a group Acceptable Daily Intake (ADI) for phosphates expressed as phosphorus of 40 mg/kg body weight (bw) per day and concluded that this ADI is protective for the human population (1).

Potassium phosphate studies

• Molecular Formula: K₃O₄P   K₃PO₄
• Molecular Weight: 212.265 g/mol
• UNII: 16D59922JU
• CAS: 7778-53-2    14887-42-4  16068-46-5  44042-47-9  1017687-06-7  1269628-80-9  1608125-41-2  2139271-06-8
• EC Number: 231-907-1  238-961-5  240-213-8  920-994-8
• PubChem Substance ID 57654540
• MDL number MFCD00036295

Synonyms:

• Tripotassium phosphate
• E340
• tri-Potassium orthophosphate
• Potassium phosphate, anhydrous
• Tripotassium phosphate,anhydrous
• Potassium phosphate tribasic anhydrous
• phosphoric acid potassium salt
• Phosphate buffer
• potassiumphosphate
• potasium phosphate
• tri potassium phosphate
• tri-potassium phosphate
• Tripotassium phosphate|
• tris-potassium phosphate
• potassium phophate
• potassium phoshate
• potassium-phosphate
• Tripotasium phosphate
• tripotassium,phosphate
• tripotassiurn phosphate
• Potassium phosphate tribasic
• Tripotassium orthophosphate
• Phosphoric acid, tripotassium salt
• Potassium orthophosphate
• Caswell No. 700A
• Phosphoric acid, potassium salt
• Potassium phosphate, tribasic

References_______________________________________________________________________

(1) EFSA Panel on Food Additives and Flavourings (FAF); Younes M, Aquilina G, Castle L, Engel KH, Fowler P, Frutos Fernandez MJ, Fürst P, Gürtler R, Husøy T, Mennes W, Moldeus P, Oskarsson A, Shah R, Waalkens-Berendsen I, Wölfle D, Aggett P, Cupisti A, Fortes C, Kuhnle G, Lillegaard IT, Scotter M, Giarola A, Rincon A, Tard A, Gundert-Remy U. Re-evaluation of phosphoric acid-phosphates - di-, tri- and polyphosphates (E 338-341, E 343, E 450-452) as food additives and the safety of proposed extension of use. EFSA J. 2019 Jun 12;17(6):e05674. doi: 10.2903/j.efsa.2019.5674.