E524: Sodium hydroxide
What is E524?
Sodium hydroxide (E524), commonly known as lye or caustic soda, is a strong alkali. In food processing it is used in carefully controlled amounts and is neutralised, so it does not remain as such in the finished product.
Origin and production
It is produced industrially by electrolysis of salt water (brine), a process that also produces chlorine and hydrogen.
Why is it used?
Dipping pretzels in a dilute lye solution before baking gives them their deep brown, glossy crust and distinctive flavour. It is also used to alkalise cocoa for darker, milder 'Dutch-processed' chocolate, to cure olives, peel fruit and vegetables, and in some crackers and snacks.
Vegan, vegetarian and halal
Sodium hydroxide is a mineral chemical and suitable for vegans and vegetarians.
Safety and regulation
E524 is authorised in the EU as an acidity regulator and has been evaluated by EFSA. It is corrosive in concentrated form, so its safety in food depends on proper dilution and neutralisation during processing.
Written by the Foodlas editorial team with AI assistance and checked against EU Regulation (EC) No 1333/2008 and EFSA scientific opinions. Last reviewed: October 14, 2026.
Sources: Regulation (EC) No 1333/2008 · EFSA — Food additives · Wikidata
Common in
Products containing E524
