ScanWise
E524

Sodium hydroxide

No known risk

Lye — processing agent, fully reacted in product.

Vegan
Yes
Vegetarian
Yes

What it is

A strong alkaline base used to rapidly raise pH, peel fruits, or alter the surface texture of baked goods.

How it is used in food

Essential for traditional German pretzel making, where a quick dip in lye water gives the pretzel its dark brown, shiny crust.

Commonly found in
  • Pretzels
  • Bagels
  • Canned olives
  • Cocoa processing

Health and safety

None in the finished food. Lye is genuinely caustic in the drum, but it is fully reacted during processing. What remains is sodium, which counts toward salt intake.

Permitted as a processing aid and acidity regulator; it is consumed by the reaction it drives.

Regulatory status

RegionStatusNotes
Australia & New Zealand
FSANZ		 Permitted Permitted under the FSANZ Food Standards Code.
European Union
EFSA / European Commission		 Permitted Authorised for food use under EU regulations (Annex II).
United States
FDA (Food and Drug Administration)		 Permitted Authorised for food use by the FDA (often GRAS for standard additives).

Identification on labels

E-number
E524

Also printed asCaustic soda · Lye

How it is made

Synthesized industrially from basic mineral and chemical feedstocks.

  1. Pretzel Glazing (Example) — Pretzels are dipped in a very dilute (often 1-3%) cold sodium hydroxide solution for a few seconds before baking.

Worth knowing

Also known as lye, this strong alkaline chemical reacts with proteins on the dough surface during baking to create the Maillard reaction.

Conclusion

There is no reason to avoid foods made with sodium hydroxide. While lye is caustic in industrial packaging, it reacts fully during baking or processing to create pretzel crusts and olives, leaving only ordinary sodium behind. EFSA permits it as a safe processing aid that is entirely consumed by the chemical reaction.

References

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Entry last reviewed 2026-07-28.

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