Sodium Hydroxide (Lye) — Hidden Processing Agent — Is It Vegan?
Also known as: Caustic soda, NaOH, E524
Vegan
No animals or animal-derived substances are involved in producing this agent.
Not required on labels
E524 when used as a food additive. Often listed as 'lye' or 'caustic soda' in artisan food descriptions.
Source
Produced industrially by the chlor-alkali process — electrolysis of brine (saltwater). Entirely inorganic.
Used In
Olive curing (gives Californian black olives their colour and flavour), pretzel and bagel lye bath (gives characteristic brown crust and chewy texture), cocoa processing (Dutch-process cocoa), hominy production, some lutefisk processing.
How to Avoid
No need to avoid — sodium hydroxide is vegan.
Editorial Notes
Lye is the defining step in making pretzels and bagels — the bread is briefly immersed in a dilute NaOH solution before baking, which produces the characteristic brown colour (Maillard reaction) and distinct chewiness. For olives, the lye treatment neutralises oleuropein (an extremely bitter compound), making olives palatable. The strong alkali is neutralised during processing and is safe at residual levels.