Sodium Hydroxide (Lye) — Hidden Processing Agent — Is It Vegan?

Vegan status: Vegan

Also known as: Caustic soda, NaOH, E524

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.

Appears on label: No. E524 when used as a food additive. Often listed as 'lye' or 'caustic soda' in artisan food descriptions.

How to avoid

No need to avoid — sodium hydroxide is vegan.

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.