Calcium hydroxide

E number E526INS 526CAS 1305-62-0

Used as an acidity regulator — Codex also lists it as firming agent.

Calcium hydroxide, or slaked lime, is a firming agent and acidity regulator. Its best-known use is nixtamalisation — soaking maize in lime water, which is what makes tortillas possible and releases the niacin in the grain.

Where it is and isn’t permitted

Status of Calcium hydroxide by jurisdiction. Every jurisdiction this site covers is listed, including those where the substance does not appear.
JurisdictionStatusScope and limitsCitation
United StatesFood and Drug AdministrationPermitted21 CFR 184.1205retrieved 2026-09-07
Codex AlimentariusCodex Alimentarius Commission / JECFAPermitted, with conditions

7 food categories

highest permitted level 2,000 mg/kg

Show every food category
  • 01.2.1.2 Fermented milks (plain), heat-treated after fermentation — GMP
  • 01.8.2 Dried whey and whey products, excluding whey cheeses — GMP
  • 02.2.1 Butter — GMP
  • 13.1.1 Infant formulae — 2,000 mg/kg
  • 13.1.2 Follow-up formulae — GMP
  • 13.1.3 Formulae for special medical purposes for infants — 2,000 mg/kg
  • 13.2 Complementary foods for infants and young children — GMP
CXS 192-1995 Table Three, INS 526and 7 further provisionsretrieved 2026-09-07

What it is made from

Made by adding water to calcium oxide, which is itself produced by heating limestone.

  • Vegan
  • Vegetarian
CAS registry number
1305-62-0
InChIKey
AXCZMVOFGPJBDE-UHFFFAOYSA-L
PubChem
CID 6093208

Every name it appears under

49 recorded names. A label may use any of them.

E number

  • E526

INS number

  • 526

CAS registry number

  • 1305-62-0

As it appears in regulation

  • Calcium hydroxide

Other names

  • Bell mine
  • Biocalc
  • BTTE
  • Calbit
  • Calcarea caustica
  • Calcium dihydoxide
  • Calcium dihydroxide
  • Calcium hydrate
  • Calcium hydroxide
  • Calcium hydroxide (Ca(OH)2)
  • Calcium hydroxide ACS grade
  • Calcium Hydroxide FCC
  • Calcium Hydroxide FCC, oxalate ID test 98%+ total alkali
  • calcium(2+) hydroxide
  • calcium(II) hydroxide
  • Caldic 1000
  • Calvit
  • CaO2
  • Caustic lime
  • E 526
  • geloeschter Kalk
  • Hydralime
  • Hydrated lime
  • Hydroxide, Calcium
  • INS NO.526
  • INS-526
  • Kalkhydrate
  • Kalziumhydroxid
  • Kemikal
  • Kentoku K 100
  • Limbux
  • Lime hydrate
  • Lime milk
  • Lime water
  • Loeschkalk
  • Milk of lime
  • NICC 3000
  • O2 Patch
  • PF5DZW74VN
  • Rhenofit CF
  • Slaked lime
  • Slaked-lime
  • Super Microstar
  • Yukijirushisakanyo

Systematic names

  • Calcium;dihydroxide

Hazard reference values

No reference value for this substance in the sources we hold.

Evidence and how bodies read it

Studies, and the differing conclusions regulators drew from them, are curated by hand rather than machine-read, and none has been written for this substance yet.

Sources for this page

  • ecfr retrieved 2026-09-07
  • gsfa retrieved 2026-09-07

Full licence terms and publisher details on Sources. How this page is built and updated: Method.

Machine-readable:/api/v1/additives/calcium-hydroxide.json