E529 - Calcium oxide

Synonyms: E529Calcium oxide

Search interest:#13312K / moin U.S.🇺🇸data from

Function:

acidity regulator

Origin:

Mineral

Products: Found in 16 products

Awareness:
×80.63

Calcium oxide (E529) is a highly alkaline compound also known as quicklime. In food processing, it is used in tiny amounts to control acidity and to support certain steps where a strong base is useful. It turns into calcium hydroxide when it meets water, so its effect in foods is to raise pH.

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At a glance

  • Name: Calcium oxide; E-number: E529
  • Role in food: controls acidity (raises pH); used in very small, food-grade amounts
  • Common form: a white, powdery solid that reacts with water to form calcium hydroxide
  • Regulatory status: authorized as a food additive in the European Union with purity rules

Why is Calcium oxide added to food?

Food makers use calcium oxide to adjust acidity. It is a strong base that reacts with water to form calcium hydroxide, which raises pH and can help set the right conditions for texture, color, and flavor during processing.1 In the European Union (EU), it is listed as an approved food additive (E529), so it may be used where specifically authorized and in line with general use rules for additives.2

What foods contain Calcium oxide?

You are most likely to find E529 listed on labels of specialty or highly processed items where pH control is needed. It is not as common as closely related bases like calcium hydroxide or calcium carbonates. Look for “calcium oxide” or “E529” in the ingredient list.

What can replace Calcium oxide?

The best substitute depends on the recipe, target pH, taste impact, and labeling needs.

How is Calcium oxide made?

Food‑grade calcium oxide is produced by heating natural calcium carbonate sources (such as limestone) to high temperatures. This “calcination” drives off carbon dioxide (CO2) and leaves calcium oxide (CaO).3 Chemically, CaO is reactive with water and quickly converts to calcium hydroxide (Ca(OH)2), releasing heat in the process.1

Is Calcium oxide safe to eat?

In the EU, calcium oxide (E529) is an authorized additive and must meet strict identity and purity criteria before use in food.23 Because it is strongly alkaline, manufacturers apply only the minimum amount needed to achieve the intended effect, as required by EU food additive rules.2 When handled correctly by industry and used within applicable regulations, its use in foods is considered acceptable by regulators.2

Does Calcium oxide have any benefits?

  • Technological benefit: It raises pH during processing, which can help achieve desired texture or stability in certain foods.
  • Nutritional note: It can contribute a small amount of calcium. Calcium is an essential mineral for bones, muscles, nerves, and normal blood clotting, though most people get calcium from foods like dairy, fortified products, and certain greens.4

Who should avoid Calcium oxide?

Calcium oxide is used in tiny, controlled amounts in foods. Still, people who must limit total calcium intake—such as those with hypercalcemia or certain kidney conditions—should follow medical advice about overall calcium from all sources.4 Anyone with concerns about alkaline additives can choose products that list different acidity regulators.

Myths & facts

  • “It’s the same as construction lime, so it can’t be safe.” Food‑grade calcium oxide must meet specific food purity standards and is used at very small levels. Industrial grades are not for eating.
  • “It stays as quicklime in food.” In the presence of moisture, CaO converts to calcium hydroxide; in practice, its effect is to raise pH rather than remain as dry quicklime.1
  • “It adds a lot of calcium to the diet.” Any calcium contribution from E529 at typical use levels is small compared with everyday calcium‑rich foods.

Calcium oxide in branded foods

On ingredient lists, look for “calcium oxide” or “E529.” It appears mainly in products where the maker needs a strong alkalizing agent during processing. Similar products from different brands may use other regulators instead, such as calcium hydroxide or sodium carbonates, so labels can differ.

References

Footnotes

  1. Calcium oxide — PubChem, National Institutes of Health (NIH). https://pubchem.ncbi.nlm.nih.gov/compound/Calcium-oxide ↩ ↩2 ↩3

  2. Regulation (EC) No 1333/2008 on food additives — EUR-Lex. https://eur-lex.europa.eu/eli/reg/2008/1333/oj ↩ ↩2 ↩3 ↩4

  3. Commission Regulation (EU) No 231/2012 laying down specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008 — EUR-Lex. https://eur-lex.europa.eu/eli/reg/2012/231/oj ↩ ↩2

  4. Calcium Fact Sheet for Health Professionals — Office of Dietary Supplements (ODS), NIH. https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/ ↩ ↩2

Popular Questions

  1. What is calcium oxide used for?

    As a food additive (E529), it’s used mainly as an acidity regulator/alkalizing agent to raise pH and sometimes as a firming agent in certain foods.

  2. What is the formula for calcium oxide?

    CaO.

  3. Is calcium oxide a compound?

    Yes—calcium oxide (CaO) is an inorganic compound, a basic oxide of calcium.

  4. Why add calcium oxide in bayer process?

    Lime (CaO) is added to Bayer liquors to react with silica and carbonate—forming insoluble calcium silicates and regenerating caustic (NaOH)—which improves clarification, reduces soda loss, and limits scaling.

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