INS 339 (i) is sodium dihydrogen phosphate, also called monosodium phosphate, and numbered E339(i) in Europe. INS 339 covers the sodium phosphates, and the sub-index reflects how much sodium the salt carries: (i) has one sodium atom and is the most acidic, (ii) is disodium hydrogen phosphate and (iii) trisodium phosphate.
It is made by partly neutralising phosphoric acid with a sodium base such as sodium carbonate or sodium hydroxide. Codex lists a wide range of uses: acidity regulator, emulsifier, emulsifying salt, humectant, raising agent, sequestrant, stabilizer and thickener.
In snacks it mostly serves as an acidity regulator and buffer. On Lay’s Rock Ridged Seafood Cheese Pizza it is grouped with acetic acid, an acetate and calcium lactate under acidity regulator, helping keep the cheesy seasoning’s sourness in balance. Being acidic, it can also serve as the acid part of some leavening systems.
