INS 524 is sodium hydroxide, also known as caustic soda or lye, numbered E524 in Europe. Codex lists it as an acidity regulator. It is made industrially by passing an electric current through salt water, the chlor-alkali process.
It is a very strong alkali, so food makers use it only in small, controlled amounts to raise pH or neutralise acids; used this way, it reacts with the acids in the food to form ordinary salts. Familiar uses include alkalising, or “Dutching”, cocoa, which darkens its colour and mellows the flavour, giving pretzels their glossy brown crust, and peeling fruit and vegetables.
On SeekSnack it appears on Pocky Choco Banana, whose label lists it as the acidity regulator, alongside sodium bicarbonate as the leavening agent and lecithin as the emulsifier.
