E338 (Phosphoric acid or Orthophosphoric Acid) is a chemical compound, polyprotic acid produced by phosphate minerals or by thermal process produced by elemental phosphorus.

It appears in the form of transparent oily liquid.

What it is used for and where

Cosmetics

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.

Fragrance. It plays a very important role in the formulation of cosmetic products as it allows perfume to be enhanced, masked or added to the final product, improving its commercial viability.  The consumer always expects to find a pleasant scent in a cosmetic product.

pH adjuster. This ingredient tends to restore the pH of a cosmetic formulation to its optimal value. The correct pH value is an essential determinant for lipid synthesis in the stratum corneum. The average physiological pH value of the face ranges between 5.67 and 5.76. The hair fibre has a pH value of 3.67.

Food

It is an ingredient labelled E338 in the European food additives list as an acidity regulator and chelating agent.

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).

Other uses

It is used in an innumerable series of applications, from the medical to the industrial sector:

• acidifier in beverages
• antioxidant in cheeses (with the exception of mozzarella and other cheeses)
• thickener in products containing meat, precooked and packaged
• anticorrosive (hydrogen phosphoric acid)
• catalyst
• fiber esterifier
• chemical binder for bonding bricks
• basaltic leaching
• non-ionic surfactant
• plutonium extraction
• pinacolic rearrangement
• hydroxyapatite for orthopedic and dental applications
• fruit yield improvement
• aluminophosphate mortar for tubular blocks
• fuel cells for stationary applications

Orthophosphoric acid studies

• Molecular Formula: H₃PO₄  H₃O₄P
• Molecular Weight: 97.994 g/mol
• UNII: E4GA8884NN
• CAS: 7664-38-2  
• DSSTox ID  DTXSID5024263
• IUPAC  phosphoric acid
• InChl=1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4)
• InChl Key      NBIIXXVUZAFLBC-UHFFFAOYSA-N
• SMILES  OP(=O)(O)O
• EC Number: 231-633-2  
• FEMA Number: 2900
• PubChem Substance ID 24898708
• MDL number MFCD00011340
• Beilstein Registry Number 1921286 
• Nikkaji    J3.746J
• UN    1805    3453
• RTECS    TB6300000
• NSC    80804
• ICSC    1008

Synonyms:

• Phosphoric acid
• U.N. 1805
• Acide phosphorique
• acidephosphorique
• acidephosphorique(french)
• acidephosphoriquesolutions
• Acido fosforico
• EVITs
• Fosforzuuroplossingen
• hydrogenphosphate
• Marphos
• NFB
• ortho-phosphoramide
• phosphoricacid(non-specificname)
• phosphoricacidsolutions
• Phosphorsaeureloesungen
• Sonac
• wc-reiniger
• White phosphoric acid
• whitephosphoricacid
• Orthophosporic acid

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.