E525 - Potassium hydroxide

At a glance

• E-number: E525; names: potassium hydroxide, food-grade lye
• What it does: acidity regulator and pH control agent; also used as a peeling aid in fruit and vegetable processing
• Where it appears: canned peeled tomatoes or peaches, some processed vegetables, certain syrups and beverages
• Labeling: “potassium hydroxide” or “E525”
• Dietary note: adds potassium; people who must limit potassium should check labels

Why is potassium hydroxide added to food?

Manufacturers use potassium hydroxide to adjust pH. By reducing excess acidity, it helps balance flavor, protect color and texture, and ensure other additives or enzymes work as intended. In the European Union, potassium hydroxide is an authorised food additive (E525) for use as an acidity regulator under food additive law.¹

It also serves as a processing aid for peeling certain fruits and vegetables. Under U.S. regulations, food-grade lye solutions made with potassium hydroxide may be used to help loosen skins before rinsing them away.²

What foods contain potassium hydroxide?

You’re most likely to find potassium hydroxide in:

• Canned peeled produce such as tomatoes or peaches (used during the peeling step)
• Some processed vegetables and legumes
• Certain beverages and syrups where pH needs fine-tuning
• A few confectionery or specialty foods that require tight pH control

On ingredient lists it will read “potassium hydroxide” or “E525.” When only pH adjustment is needed, other agents may be chosen instead, such as sodium hydroxide, potassium carbonates, or sodium carbonates.

What can replace potassium hydroxide?

Substitutes depend on the recipe and target pH:

• Other alkaline regulators: sodium hydroxide, potassium hydrogen carbonate, potassium carbonates, sodium bicarbonate
• If more acidity is needed instead of alkalinity: citric acid, acetic acid, or phosphoric acid

Food makers choose the option that reaches the desired pH with the least impact on taste and texture.

How is potassium hydroxide made?

Most food-grade potassium hydroxide is produced by electrolyzing a purified potassium chloride (KCl) brine in a membrane cell, which yields KOH, chlorine, and hydrogen. The resulting solution is then concentrated and purified to meet food specifications.³

Is potassium hydroxide safe to eat?

Potassium hydroxide is a very strong base and is caustic in concentrated form, but in foods it is used in tiny amounts under strict specifications and good manufacturing practices. In the EU, specifications for E525 (identity and purity) are set in Commission Regulation (EU) No 231/2012.⁴ In the U.S., its use as a peeling aid for fruits and vegetables is specifically regulated, and products are thoroughly washed after treatment.² The compound’s corrosive nature is well known in concentrated solutions, which is why manufacturing and handling rules require careful control.³

Does potassium hydroxide have any benefits?

When used correctly, potassium hydroxide:

• Stabilizes taste by reducing sharp acidity
• Helps maintain color and texture in sensitive foods
• Improves processing steps (for example, controlled peeling and pH adjustment for consistent quality)

Who should avoid potassium hydroxide?

Because potassium hydroxide contributes potassium, people who must limit potassium—such as some individuals with chronic kidney disease—should review labels and follow medical advice about potassium intake.⁵

Myths & facts

• Myth: It’s the same as household drain cleaner.
  Fact: While the chemical is similar, food-grade potassium hydroxide is highly controlled, used in tiny amounts, and foods are neutralized or washed so the final product is safe to eat.
• Myth: It stays caustic in your food.
  Fact: In regulated food uses, it’s either washed off (peeling) or neutralized by the food’s natural acids; the final pH is kept within normal, edible ranges.
• Myth: It always adds a “soapy” taste.
  Fact: At proper levels, it’s not used to flavor foods; it’s a tool for precise pH control.

Potassium hydroxide in branded foods

You may see potassium hydroxide on labels of:

• Canned peeled tomatoes or peaches
• Some jarred or canned vegetables
• A few beverages or syrups that need pH adjustment

Label wording will typically be “potassium hydroxide” or “E525.” If you’re watching potassium intake, compare similar products and choose those without potassium-based additives when possible.

References

Footnotes

1. Regulation (EC) No 1333/2008 on food additives — EUR-Lex. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32008R1333 ↩

2. 21 CFR 173.315 — Chemicals used in washing or to assist in the peeling of fruits and vegetables — eCFR (FDA). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-173/section-173.315 ↩ ↩²

3. Potassium Hydroxide — PubChem, NIH. https://pubchem.ncbi.nlm.nih.gov/compound/Potassium-hydroxide ↩ ↩²

4. Commission Regulation (EU) No 231/2012 laying down specifications for food additives — EUR-Lex. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32012R0231 ↩

5. Potassium in diet — MedlinePlus, NIH. https://medlineplus.gov/ency/article/002413.htm ↩