E526 - Calcium hydroxide

At a glance

• What it is: A strong, food-grade base made by hydrating quicklime (calcium oxide).
• What it does: Controls pH (acidity/alkalinity), firms plant tissues, and aids processing steps.
• Where it’s used: Lime-treated corn for tortillas and masa, some fruit and vegetable preparations, and various regulated food categories.
• Taste and texture: Mildly alkaline; helps maintain crunch and structure in some foods.
• Regulation: Authorized in the EU as E526 and affirmed as GRAS (Generally Recognized As Safe) in the U.S. when used under good manufacturing practice.

Why is calcium hydroxide added to food?

Food makers use calcium hydroxide to adjust pH (reduce acidity) and stabilize foods during processing, which can protect color, flavor, and texture. It is permitted in the U.S. as a pH control agent and as a processing aid under current good manufacturing practice.¹ In the EU, it is an approved additive (E526) with defined identity and purity specifications and authorized uses.²

What foods contain calcium hydroxide?

You’ll most often see calcium hydroxide where an alkaline step is needed or where firmness matters. Examples include:

• Lime-treated corn (nixtamal) used to make masa and tortillas, where calcium hydroxide is added to the cooking/soaking water.³
• Various EU-authorized categories such as certain fruit and vegetable preparations, confectionery, and other foods where a pH regulator or processing aid is needed, typically at levels set by “quantum satis” (as needed, not more).²

On ingredient labels it may appear as “calcium hydroxide,” “slaked lime,” or “E526” (in regions that use E-numbers).

What can replace calcium hydroxide?

Substitutes depend on the job you need done:

• For pH control (to reduce acidity): other approved bases like sodium hydroxide or potassium hydroxide can sometimes be used. For milder pH changes, carbonate salts like sodium carbonates may be chosen.
• For firming produce: calcium salts such as calcium chloride or calcium sulphate are common options.
• For balancing tartness: acids like citric acid may be paired with or swapped in, depending on the recipe.

Always note that each additive behaves differently, so direct one-to-one swaps may change taste or texture.

How is calcium hydroxide made?

Calcium hydroxide is produced by hydrating calcium oxide (quicklime) with water, a reaction known as “slaking.” Food-grade E526 must meet defined identity and purity criteria in the EU specifications for food additives.⁴ JECFA (the Joint FAO/WHO Expert Committee on Food Additives) also publishes specifications for food use.⁵

Is calcium hydroxide safe to eat?

In the U.S., calcium hydroxide is affirmed as GRAS for use as a pH control agent and processing aid, provided it is used in line with current good manufacturing practice.¹ EFSA (the European Food Safety Authority) has re-evaluated calcium hydroxide (E526) and found no safety concern at the reported uses and use levels.² JECFA allocated an “ADI not specified” for calcium from calcium salts such as calcium hydroxide, indicating low concern at typical use levels.⁵

As a concentrated chemical, calcium hydroxide is a strong alkali and can be caustic before it is diluted and properly used in foods.⁶ Food manufacturing controls and regulations are designed to ensure safe levels in the final product.¹

Does calcium hydroxide have any benefits?

Beyond pH control and texture, calcium hydroxide enables nixtamalization, the traditional alkaline treatment of maize. This process improves dough performance and flavor and can increase calcium content; it also improves the nutritional quality of maize products compared to untreated grain.³

Who should avoid calcium hydroxide?

Most people do not need to avoid foods containing E526 when it is used as intended. However, individuals on medically supervised low-calcium diets, those with conditions like hypercalcemia (high blood calcium), or people with certain kidney disorders should consult a healthcare professional about overall calcium intake, including small amounts that may come from additives.⁷

Myths & facts

• “It’s the same as quicklime.” Not quite. Quicklime is calcium oxide; calcium hydroxide is made by carefully adding water to quicklime and is the food-grade form used in regulated amounts.⁴
• “It makes food caustic.” In concentrated form it is caustic, but in food it is used under strict controls and at safe levels, with the final product meeting legal limits.¹⁶
• “It’s ‘lime’ like the fruit.” No. In this context “lime” refers to mineral lime (calcium compounds), not citrus fruit.

Calcium hydroxide in branded foods

On labels, you may see “calcium hydroxide,” “slaked lime,” or “E526.” It often appears in tortillas and masa products made from lime-treated corn, and in some preserved fruit and vegetable items where firmness or pH control is needed. Availability and labeling vary by region; European labels may use the E-number, while U.S. labels typically use the name.

References

Footnotes

1. 21 CFR 184.1205 — Calcium hydroxide (GRAS). ecfr.gov https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184/section-184.1205 ↩ ↩² ↩³ ↩⁴

2. Re-evaluation of calcium hydroxide (E 526) as a food additive — EFSA Journal. efsa.europa.eu https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2013.3649 ↩ ↩² ↩³

3. Maize processing and nixtamalization — FAO (Food and Agriculture Organization). fao.org https://www.fao.org/3/t0234e/T0234E06.htm ↩ ↩²

4. Commission Regulation (EU) No 231/2012 — Specifications for food additives (E 526: Calcium hydroxide). eur-lex.europa.eu https://eur-lex.europa.eu/eli/reg/2012/231/oj ↩ ↩²

5. Calcium hydroxide — JECFA Specifications (FAO/WHO). fao.org https://www.fao.org/food/food-safety-quality/scientific-advice/jecfa/jecfa-additives/specs/en/ ↩ ↩²

6. NIOSH Pocket Guide to Chemical Hazards: Calcium hydroxide. cdc.gov https://www.cdc.gov/niosh/npg/npgd0085.html ↩ ↩²

7. Calcium Fact Sheet for Health Professionals — NIH Office of Dietary Supplements. ods.od.nih.gov https://ods.od.nih.gov/factsheets/Calcium-Consumer/ ↩