E525 Potassium hydroxide (Caustic potash)

E525Acidity regulatorsOrigin: Mineral

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The short answer

Potassium hydroxide (E525) is a strong alkali used to adjust pH and in some cocoa and processing steps. It is vegan, gluten-free and kosher, and the food-grade amounts are small and neutralized.

86/100

Generally safe

Fine for most people at normal amounts.

E-numberE525

Comes fromMineral

What it doesAcidity regulators

Glycemic index—

Daily limitNot set

Also calledE525, Caustic potash

Rules by country

🇺🇸 US FDAApproved

🇪🇺 European UnionApproved

🇨🇦 Health CanadaApproved

CaliforniaNo extra rules

Permitted in the US, EU and Canada as a pH control agent in food processing.

Daily limit: Experts haven’t set a number because normal food amounts are far below any level of concern.

What is it?

Potassium hydroxide is the potassium form of lye. Food makers use it to raise pH, and it reacts with acids in the food to form potassium salts, which are harmless at food levels.

Where it comes from: Made by electrolysis of potassium chloride brine. Food-grade alkali is used to adjust pH and in some cocoa treatments.

Why it’s in food

Raises pH in processing
Used in some cocoa treatments
Potassium version of sodium hydroxide

Often found in

Cocoa powderProcessed foodsProcessing aids

Also listed as: E525, Caustic potash, Potash lye

Health & gut impact

Handling hazardUnder study

The chemical is caustic and burns skin and eyes in concentrated form. Finished food contains trace residue, not a caustic level, so the concern is with the bulk chemical.

JECFA evaluation of potassium hydroxide

What can I use instead?

Potassium carbonate (E501)

Ratio: A gentler alkali for cocoa and baking

Best for: Cocoa and baked goods

Sodium bicarbonate (E500)

Ratio: A mild alkali for baking

Best for: Baking

More acidity regulators:

Acetic acid E260Acetic acid (E260) is the acid that makes vinegar sour. Diluted in food it is considered safe. The hazard is the concentrated factory form, not a splash of vinegar.Generally safe Ammonium carbonate E503Ammonium carbonate (E503) is a traditional leavening agent that makes thin cookies and crackers crisp. It breaks down into gas in the oven, so little of it stays in the finished food.Generally safe Calcium acetate E263Calcium acetate (E263) is a calcium salt of acetic acid that steadies acidity and adds a mild tang in processed foods. It is vegan and gluten-free, and it is also a prescription phosphate binder at much higher doses.Generally safe Calcium carbonate E170Calcium carbonate (E170) is ground limestone, the same calcium found in antacids. It adds calcium to plant milks and flour and is very safe.Generally safe

Common questions

Is potassium hydroxide the same as lye?

It is the potassium form of lye. The sodium form is the one usually called lye.

Does it stay in the food?

Trace amounts can remain, but food makers neutralize the alkali so the product ends up close to neutral.

Is Potassium hydroxide safe?

Generally safe (86/100). Permitted in the US, EU and Canada as a pH control agent in food processing.

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Scientific sources & regulatory citations

EFSA OpenFoodTox: E525
JECFA evaluation of potassium hydroxide

INS 525 · CAS 1310-58-3