Calcium oxide
1305-78-8 · Aetzkalk · Airlock · BDFERM BIOSPRAY · Bell CML(E) · Bell CML(P) · Branntkalk · Burned lime · Burnt lime · C7X2M0VVNH · Calcia · Calcia (CaO) · Calcium monoxide · Calcium oxide · Calcium oxide (CaO) · Calcium oxide (JP17) · Calcium oxide, 99.995% trace metals basis · Calcium oxide, CP · Calcium oxide, p.a., 95.0% · Calcium oxide, SAJ first grade, >=98.0% · Calcium oxide, SAJ special grade, >=98.0% · Calcium oxide, Vetec(TM) reagent grade · Caloxal CPA · Caloxol CP2 · CALOXOL W 3 · Caloxol W3 · CALX · Calx usta · Calxyl · Caswell No. 147A · CCRIS 7496 · Chaux vive · CML 21 · CML 31 · CML 35 · Desical P · E 529 · EPA Pesticide Chemical Code 075604 · EVECODE ECO FRIENDLY MULTI SANITIZERspray · EVECODE Eco-Friendly Safe SanitizerSpray · Gebrannter kalk · heavy calcium oxide · HSDB 1615 · INS NO.529 · INS-529 · Kalziumoxid · Lime (Calcium Oxide) · Lime (cao) · Lime (USP) · Lime [USP] · Lime, burned · Lime, meets USP testing specifications · oxocalcium · Oxyde de calcium · Pebble lime · Quick lime · Quicklime · Rhenosorb C · Rhenosorb F · Unslaked lime · Vesta PP · Wapniowy tlenek · E529 · 529 · calcium oxide · Calcium oxide · Calcium oxide · Calciumoxid · Calciumoxide · Kalcija oksīds · Kalcijev oksid · Kalcio oksidas · Kalcium-oxid · Kalciumoxid · Kalsiumoksidi · Kaltsiumoksiid · Ossido di calcio · Ossidu tal-kalċju · Oxid de calciu · Oxid vápenatý · Oxyde de calcium · Tlenek wapnia · Óxido de calcio · Οξείδιο του ασβεστίου · Калциев оксидE number E529INS 529CAS 1305-78-8
Listed as an acidity regulator by Canada, Codex and the US.
Listed as acidity regulators (CA, US, Codex) · anticaking agents (US) · firming agents (US) · flour treatment agents (Codex) · dough strengtheners (US) · nutrient supplements (US) · texturisers (US) · processing aids (US)
- Canada: Acidity regulator — Health Canada, List of Permitted Acidity Regulators and Acid-Reacting Materials (List 10)
- United States: pH control agent — FDA, Substances Added to Food: CALCIUM OXIDE
- Codex Alimentarius: Acidity regulator — CXS 192-1995 Table One, INS 529
- United States: Anticaking agent or free-flow agent — FDA, Substances Added to Food: CALCIUM OXIDE
- United States: Firming agent — FDA, Substances Added to Food: CALCIUM OXIDE
- Codex Alimentarius: Flour treatment agent — CXS 192-1995 Table One, INS 529
- United States: Dough strengthener — FDA, Substances Added to Food: CALCIUM OXIDE
- United States: Nutrient supplement — FDA, Substances Added to Food: CALCIUM OXIDE
- United States: Texturizer — FDA, Substances Added to Food: CALCIUM OXIDE
- United States: Processing aid — FDA, Substances Added to Food: CALCIUM OXIDE

Calcium oxide, or quicklime, is an alkaline acidity regulator and processing aid used in sugar refining, maize processing and dairy.
Where it is and isn’t permitted
| Jurisdiction | Status | Scope and limits | Citation |
|---|---|---|---|
| Australia and New Zealand | Permitted, with conditions | 54 food categories no numerical limit (good manufacturing practice) Show every food category
| Food Standards Code, Schedule 15, S15—5and 53 further provisionsretrieved 2026-10-17 |
| Canada | Permitted, with conditions | no numerical limit (good manufacturing practice) 7 permitted uses Show every permitted use
| Health Canadaand 6 further provisionsretrieved 2026-10-17 |
| European Union | Permitted, with conditions | 68 food categories Show every food category
| Regulation (EC) No 1333/2008, Annex IIand 67 further provisionsretrieved 2026-10-18 |
| Great Britain | Permitted, with conditions | 66 food categories Show every food category
| Assimilated Regulation (EC) No 1333/2008, Annex II (as at 28 June 2024)and 65 further provisionsretrieved 2026-10-18 |
| Japan | Permitted, with conditions | Designated additive: Appended Table 1, item 173, 酸化カルシウム (“Calcium Oxide” in the unofficial English translation). …Designated additive: Appended Table 1, item 173, 酸化カルシウム (“Calcium Oxide” in the unofficial English translation). Standards for use — Specifications and Standards for Foods, Food Additives, etc. (MHW Notification No. 370 of 1959), Part II (Food Additives), F (Standards for use): The Notification sets no standard for use (使用基準) for this additive, so it is not restricted there to particular foods or amounts. Compositional specifications for this additive, in the same Notification, are not imported and are not shown here; nor are the general rules in F 添加物一般, which apply to every additive. | Regulations for Enforcement of the Food Sanitation Act (MHW Ordinance No. 23 of 1948), Appended Table 1retrieved 2026-10-18 |
| South Korea | Permitted, with conditions | Designated food additive: Standards and Specifications for Food Additives, Part III, 1. …Designated food additive: Standards and Specifications for Food Additives, Part III, 1. 일반식품첨가물 (general food additives), 산화칼슘 (“Calcium Oxide”, the English the Code prints beside it); the Code marks it as also usable as a nutrient fortifier; 3. 영양강화제 (nutrient fortifiers), 산화칼슘; nutrient: 칼슘(Ca); the Code marks it as also usable as a general food additive. Main use (주용도) of 산화칼슘: 산도조절제. Standard for use (사용기준) of 산화칼슘: (1) [to be used under the general standard for use in II. 2. 1), the minimum amount that achieves the technical effect, with no limit set for this additive in particular] “II. 2. 1)의 규정에 따라 사용하여야 한다.” The Korean is the standard as published. There is no official English translation of the current Code (the English version on MFDS’s website is the 2020 edition and has no legal effect); the English in square brackets is this site’s description of what each sentence does, not a translation of the foods or the levels. Compositional specifications (Part IV) are not imported, nor are the general standards in Part II, which apply to every additive. | Standards and Specifications for Food Additives (식품첨가물의 기준 및 규격), MFDS Notification, Part III (Standards for use, by item)retrieved 2026-10-18 |
| United States | Permitted | 21 CFR 184.1210retrieved 2026-10-17 | |
| Codex Alimentarius | Permitted, with conditions | 1 food category no numerical limit (good manufacturing practice) | CXS 192-1995 Table Three, INS 529and 1 further provisionretrieved 2026-09-07 |
How much is permitted
A listing usually limits the quantity as well as the food. Only one of the forms that takes is a figure: quantum satis and good manufacturing practice permit the amount the technological effect requires and no more, which is a limit rather than the absence of one. Figures below are the range across every food category this page is listed in, and categories differ between regulators — see how much is permitted.
| Australia and New Zealand | — | 54 GMP |
|---|---|---|
| Canada | — | 6 GMP, 1 no quantity stated |
| European Union | — | 46 several limits, 22 no quantity stated |
| Great Britain | — | 66 quantum satis |
| Japan | — | 1 no quantity stated |
| South Korea | — | 1 no quantity stated |
| United States | — | 1 no quantity stated |
| Codex Alimentarius | — | 2 GMP |
No regulator sets a figure for Calcium oxide. That is not an absence of control: where the listing says quantum satis or good manufacturing practice, the quantity is limited to what the effect requires.
What it is made from
Produced by heating limestone to drive off carbon dioxide. It reacts vigorously with water to form calcium hydroxide.
- Vegan
- Vegetarian
Compare other additives on the dietary indexes.
- CAS registry number
- 1305-78-8
- InChIKey
- ODINCKMPIJJUCX-UHFFFAOYSA-N
- PubChem
- CID 14778
The two specifications, compared
The European Union sets identity and purity by regulation; JECFA publishes its own through FAO, advisory until a country adopts it. Both documents are below in full. These are the parameters each puts a number on.
| Parameter | European Union | JECFA |
|---|---|---|
| Assay | no less than 95 % | no less than 95 % |
| Lead | no more than 2 mg/kg | no more than 2 mg/kg |
| Arsenic | no more than 3 mg/kg | — |
The two documents state the same figures for every parameter compared here.
How the EU defines it
The legal specification an additive must meet to be sold as this E number in the EU — what it is, how it may be made, and the purity it must reach. From Commission Regulation (EU) No 231/2012.
E 529 Calcium oxide
Synonyms: Burnt lime
Assay, identification and purity criteria
Description and assay
- Einecs
- 215-138-9
- Chemical name
- Calcium oxide
- Chemical formula
- CaO
- Molecular weight
- 56,08
- Assay
- Content not less than 95,0 % on the ignited basis
- Description
- Odourless, hard, white or greyish white masses of granules, or white to greyish powder
Identification
- Test for alkali
- Passes test
- Test for calcium
- Passes test
- Reaction with water
- Heat is generated on moistening the sample with water
- Solubility
- Slightly soluble in water. Insoluble in ethanol. Soluble in glycerol
Purity criteria
- Loss on ignition
- Not more than 10,0 % (ca. 800 °C to constant weight)
- Acid insoluble matter
- Not more than 1,0 %
- Barium
- Not more than 300 mg/kg
- Magnesium and alkali salts
- Not more than 3,6 %
- Fluoride
- Not more than 50 mg/kg
- Arsenic
- Not more than 3 mg/kg
- Lead
- Not more than 2 mg/kg
How JECFA defines it
The international specification for identity and purity, prepared by the Joint FAO/WHO Expert Committee on Food Additives and published by FAO. It is a different document from any above, written by a different body and revised on its own cycle; it is advisory, and a country adopts it or does not.
INS 529 Calcium Oxide
Synonyms: Lime; INS No. 529
Assay, identification and purity criteria
Description and assay
- Specification history
- Prepared at the 19th JECFA (1975), published in NMRS 55B (1976) and in FNP 52 (1992). Metals and arsenic specifications revised at the 59th JECFA (2002). An ADI ‘Not limited’ was established at the 9th JECFA (1965).
- Chemical names
- Calcium oxide
- C.A.S. number
- 1305-78-8
- Chemical formula
- CaO
- Formula weight
- 56.08
- Assay
- Not less than 95.0% after ignition
- DESCRIPTION
- Odourless, hard, white or greyish white masses or granules, or white to greyish white powder
- FUNCTIONAL USES
- Alkali, dough conditioner, yeast food
- METHOD OF ASSAY
- accurately weigh the residue and dissolve it in 20 ml of dilute hydrochloric acid TS. Cool the solution, dilute with water to 500 ml and mix. Pipet 50 ml of this solution into a suitable container and add 50 ml of water, then add 15 ml of sodium hydroxide TS, 40 mg of murexide indicator preparation and 3 ml of naphthol green TS, and titrate with 0.05 M disodium ethylenediamine tetraacetate until the solution is deep blue in colour. Each ml of 0.05 M disodium ethylenediamine tetraacetate is equivalent to 2.804 mg of CaO.
Identification
- Solubility (Vol. 4)
- Slightly soluble in water, insoluble in ethanol, soluble in glycerol (Caution: Protect eyes when adding water)
- Reaction with water
- Moisten the sample with water; heat is generated (Caution: Protect eyes when adding water).
- Test for alkali
- The sample is alkaline to moistened litmus paper
- Test for calcium (Vol. 4)
- Passes test
Purity criteria
- Loss on ignition (Vol. 4)
- Not more than 10% (1 g, about 800 o to constant weight)
- Barium
- Not more than 0.03% Cautiously mix 1.5 g of the sample with 10 ml water, add 15 ml of dilute hydrochloric acid TS, dilute to 30 ml with water and filter. To 20 ml of the filtrate add 2 g of sodium acetate, 1 ml of dilute acetic acid TS and 0.5 ml of potassium chromate TS and allow to stand for 15 min. The turbidity of the solution is not greater than that of a control prepared by adding water to 0.3 ml of barium standard solution (1.779 g barium chloride in 1000 ml of water) to make to 20 ml, adding 2 g of sodium acetate, 1 ml of dilute acetic acid TS and 0.5 ml of potassium chromate TS and allowing to stand for 15 min.
- Magnesium and alkali salts
- Not more than 3.6% Dissolve 500 mg of the sample in 30 ml of water and 15 ml of dilute hydrochloric acid TS. Heat the solution and boil for 1 min. Add rapidly 40 ml of oxalic acid TS and stir vigorously. Add 2 drops of methyl red TS and neutralize the solution with ammonia TS to precipitate the calcium completely. Heat the mixture on a steam bath for 1 h, cool, dilute to 100 ml with water, mix well and filter. To 50 ml of the filtrate carefully add 0.5 ml of concentrated sulfuric acid, evaporate to dryness and ignite to constant weight in a tared platinum crucible.
- Acid insoluble matter
- Not more than 1% Slake 5 g of the sample, mix with 100 ml of water and sufficient hydrochloric acid, added dropwise, to effect solution. Boil the solution, cool, add hydrochloric acid, if necessary, to make the solution distinctly acid, and filter through a tared crucible. Wash the residue with water until free of chlorides, dry at 105 o for 1 h, cool, and weigh.
- Fluoride (Vol. 4)
- Not more than 50 mg/kg (Method I or III)
- Lead (Vol. 4)
- Not more than 2 mg/kg Determine using an atomic absorption technique appropriate to the specified level. The selection of sample size and method of sample preparation may be based on the principles of the method described in Volume 4, “Instrumental Methods.” Ignite at approximately 800 o about 1 g of the sample to constant weight,
Authorised in other additives, enzymes, flavourings and nutrients
These authorisations are not for use in food. They let this substance be used inside another additive, a food enzyme, a flavouring or a nutrient preparation — often as a carrier — and it reaches food only as part of that product. Annex III to Regulation (EC) No 1333/2008.
| Part | May be used in | Maximum level | Citation |
|---|---|---|---|
| Annex III, Part 2: Food additives other than carriers in food additives | All food additive preparationsAuthorised as a member of Table 1 of Part 6, listed as "Table 1" Note (1): Except enzymes authorised as food additives. | quantum satis | Regulation (EC) No 1333/2008, Annex III, Part 2, via Table 1 of Part 6 |
| Annex III, Part 3: Food additives including carriers in food enzymes | Food enzymesCan be used as a carrier: Yes Note (1): Including enzymes authorised as food additives. | In enzyme preparation: quantum satis In final food except beverages: quantum satis In beverages: quantum satis | Regulation (EC) No 1333/2008, Annex III, Part 3 |
| Annex III, Part 4: Food additives including carriers in food flavourings | All flavouringsAuthorised as a member of Table 1 of Part 6, listed as "Table 1" | quantum satis | Regulation (EC) No 1333/2008, Annex III, Part 4, via Table 1 of Part 6 |
| Annex III, Part 5, Section A: Food additives added in nutrients except in nutrients intended to be used in foodstuffs listed in Part E, point 01.10, of Annex II and foodstuffs for infants and young children listed in Part E, point 13.1, of Annex II | All nutrientsCan be used as a carrier: Yes | quantum satis | Regulation (EC) No 1333/2008, Annex III, Part 5, Section A |
Every name it appears under
85 recorded names. A label may use any of them.
E number
- E529
INS number
- 529
CAS registry number
- 1305-78-8
As it appears in regulation
- Calcium oxide
Other names
- Aetzkalk
- Airlock
- BDFERM BIOSPRAY
- Bell CML(E)
- Bell CML(P)
- Branntkalk
- Burned lime
- Burnt lime
- C7X2M0VVNH
- Calcia
- Calcia (CaO)
- Calcium monoxide
- Calcium oxide
- Calcium oxide (CaO)
- Calcium oxide (JP17)
- Calcium oxide, 99.995% trace metals basis
- Calcium oxide, CP
- Calcium oxide, p.a., 95.0%
- Calcium oxide, SAJ first grade, >=98.0%
- Calcium oxide, SAJ special grade, >=98.0%
- Calcium oxide, Vetec(TM) reagent grade
- Caloxal CPA
- Caloxol CP2
- CALOXOL W 3
- Caloxol W3
- CALX
- Calx usta
- Calxyl
- Caswell No. 147A
- CCRIS 7496
- Chaux vive
- CML 21
- CML 31
- CML 35
- Desical P
- E 529
- EPA Pesticide Chemical Code 075604
- EVECODE ECO FRIENDLY MULTI SANITIZERspray
- EVECODE Eco-Friendly Safe SanitizerSpray
- Gebrannter kalk
- heavy calcium oxide
- HSDB 1615
- INS NO.529
- INS-529
- Kalziumoxid
- Lime (Calcium Oxide)
- Lime (cao)
- Lime (USP)
- Lime [USP]
- Lime, burned
- Lime, meets USP testing specifications
- oxocalcium
- Oxyde de calcium
- Pebble lime
- Quick lime
- Quicklime
- Rhenosorb C
- Rhenosorb F
- Unslaked lime
- Vesta PP
- Wapniowy tlenek
Systematic names
- calcium oxide
Hazard reference values
| Type | Value | Population | Assessed by | Opinion |
|---|---|---|---|---|
| ADI | not limited | — | JECFA | 1965 |
Evidence and how bodies read it
Studies, and the differing conclusions regulators drew from them, are curated rather than machine-read, and none has been written for this substance yet.
Common questions
Assembled from what is above, in the words the questions are usually asked in. Each answer is the same statement the relevant section makes, with the same citations behind it.
- What is E 529?
- E 529 is Calcium oxide. Calcium oxide, or quicklime, is an alkaline acidity regulator and processing aid used in sugar refining, maize processing and dairy.
- What is Calcium oxide used for in food?
- It is listed as an acidity regulator — the role Canada, Codex and the US assign it. This page shows every function each regulator records, with the citation for each.
- Where is Calcium oxide permitted?
- Of the seven regulators this site reads, Australia and New Zealand, Canada, the EU, Great Britain, Japan, South Korea, the US and the Codex standard permit it. Each permission is for named foods at named levels, not a blanket one; the table on this page gives them with citations.
- Is Calcium oxide vegan?
- Yes. Calcium oxide is not derived from animals, and is suitable for vegetarians. This page says what it is made from and how.
Sources for this page
- anz retrieved 2026-10-17
- ca retrieved 2026-10-17
- eu retrieved 2026-10-18
- gb retrieved 2026-10-18
- jp retrieved 2026-10-18
- kr retrieved 2026-10-18
- ecfr retrieved 2026-10-17
- gsfa retrieved 2026-09-07
- euspecs retrieved 2026-10-18
- jecfaspecs retrieved 2026-09-23
Full licence terms and publisher details on Sources. How this page is built and updated: Method.
Machine-readable: a JSON record of this additive is given on request —how to ask for access.
Follow changes to Calcium oxide:Atom feed — regulatory events, and any change the weekly refresh detects in its provisions.