Table 1.
Chemical properties of calcium salts, sources, and uses 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23
| Type of calcium a | Formula* | Percent bioavailability | Molecular weight | Solubility | Sensory properties | Source | Uses | Feasibility | Approved by |
|---|---|---|---|---|---|---|---|---|---|
| Calcium oxide (quicklime) | CaO | 71 | 56 |
Soluble in water, forming calcium hydroxide; soluble in acids, glycerol, and sugar solution; practically insoluble in alcohol. 23.3 mmol/L |
Colorless, cubic, white crystals; odorless; slightly bitter taste | From heating limestone, coral, seashells, or chalk, which are mainly CaCO3, to drive off carbon dioxide. Mainly calcium carbonate | Used as a nutrient and/or dietary supplement in animal drugs, feeds, clarification of cane and beet sugar juices | Readily absorbs oxygen and water from the air. May be difficult to use directly–immediately absorbs water after soil application | U.S. FDA |
| Calcium hydroxide (slaked lime) | Ca(OH)2 | 54 | 74 |
Soluble in boiling water, acid, glycerol, sugar, or ammonium chloride solution and insoluble in alcohol. 25 mmol/L |
Hexagonal crystals or soft granules or powder; odorless; slightly bitter alkaline taste | Formed when water is added to calcium oxide | Used as calcium salts, causticizing soda, purification of sugar juices, food additive as buffer and neutralizing agent, shell‐forming agent (poultry) | U.S. FDA/EFSA | |
| Calcium silicate | Ca2O4Si | 50 | 116 | Insoluble in water | White or creamy colored, free‐floating powder | Occurs naturally in wollastonite as calcium metasilicate; combination of calcium ions (from limestone, dolomite, etc.) and silicate ions (from silica) | Used as an indirect food additive; as an anticaking agent in animal feed; and as solid diluent | Tolerance 2% and 5% | U.S. FDA |
| Calcium carbonate b | CaCO3 | 40 | 100 |
Insoluble in alcohol, practically insoluble in water; soluble in dilute acids. 0.153 mmol/L |
White hexagonal/orthorhombic crystals or powder (calcite; argonite; vaterite); odorless; colorless; chalky, soapy, or lemony taste | Rock‐derived (marble and limestone) and from eggshell and fishbone | Used as a direct food additive and nutrient supplement, as a dough strengthener, firming agent, pH control agent, stabilizer, and thickener | U.S. FDA/EFSA | |
| Hydroxyapatite | Ca5(PO4)3(OH) | 40 | 502 | 0.08 mmol/L | – | – | – | Highly stable | – |
| Calcium phosphate tribasic | Ca3(PO4)2 | 38 | 310 |
Insoluble in alcohol and acetic acid, and soluble in dilute hydrochloric acid and nitric acid. Slightly soluble in water. 0.064 mmol/L |
White amorphous, or crystalline powder; odorless; sandy or bland taste. | Rock‐derived, as oxydapatit, voelicherite, and whitlockite. Manufactured from phosphate rock, silica, wet‐process phosphoric acid, and soda ash. Also found in cow's milk | Used as a supplement in livestock and poultry feeds; as food additives to control the pH in doughs and lard, as a yeast nutrient in flour | U.S. FDA | |
| Calcium chloride | CaCl2 | 36 | 111 |
Extremely soluble in water. 6712 mmol/L |
White cubic crystals or powder; colorless; odorless; taste threshold in potable water is 150–350 ppm. Salty, bitter taste | Isolated from brine | Used for melting ice and snow, and as a dust suppressant | U.S. FDA/EFSA | |
| Calcium formate | Ca(HCOO)2 | 31 | 130 | Soluble in water | Orthorhombic crystals or crystalline powder; white or pale yellow; slight acetic acid‐like odor | Manufactured from Ca(OH)2 and CO at high temperature and pressure | Used as a preservative for silage, food; for animal feed | ||
| Calcium phosphate dibasic | CaHPO4 | 30 | 136 |
Soluble in hydrochloric acid, nitric acid, acetic acid, and ammonium citrate solution. Insoluble in ethanol. 1.84 mmol/L |
White powder or crystalline solid; sandy or bland taste; odorless | Made from calcium carbonate and phosphoric acid | Used in powdered drink mixes (buffering agent), effervescent tablets, antacids, baking products (leavening agent), animal feeds, and mineral supplements | Nonhygroscopic, relatively stable material. Should be stored in a well‐closed container in a dry place | U.S. FDA/EFSA/Health Canada |
| Calcium sulfate | CaSO4 | 29 | 136 |
Soluble in water. 15.3 mmol/L |
Natural anhydrite crystals orthorhombic, color varies (white, blue, gray, or reddish tinge); odorless; tasteless | Made from calcium chloride and sol sulfate | Used in making tofu and water treatment | Store in a well‐closed container | U.S. FDA |
| Calcium acetate | C4H6O4Ca | 25 | 158 |
Soluble in water; slightly soluble in alcohol; needles, granules, or powder form. 2364 mmol/L |
Brown, gray, or white powder, amorphous or crystalline; slight odor of acetic acid; bitter taste | Action of pyroligneous acid on calcium hydroxide | Used as a food stabilizer and thickener for gelatins and puddings; as an antifoam additive; as an antimold agent in bakery goods; and as a firming agent for potatoes | Decomposes on heating; very hygroscopic; needs to be stored tightly | U.S. FDA |
| Calcium malate | C4H4CaO5 | 23 | 172 | Slightly soluble in water | White powder | – | Used as an acidity regulator and flavor enhancer | ||
| Calcium glycinate | C4H8CaN2O4 | 21 | 188 | Soluble in water | Used as a dietary supplement | ||||
| Tricalcium citrate | Ca3(C6H5O7)2 | 21 | 498 |
More soluble at low temperatures (advantage for cold and hot food processing). 2.006 mmol/L |
White powder; odorless; neutral tasting | A by‐product in the manufacture of citric acid | In the production of citric acid and other citrates; improvement of baking properties of flour; as a dietary supplement; as a sequestrant, buffer, and firming agent in foods | ||
| Calcium citrate | Ca3(C6H5O7)2 | 21–24 | 498 |
Insoluble in alcohol, soluble in 1050 parts cold water; somewhat more soluble in hot water; tetrahydrate. 1.49 mmol/L |
Colorless or white powder, odorless; tart, acidic taste | Rock‐derived. Calcium sourced from marble or limestone bound with citric acid | Used as a general‐purpose food additive, as a nutrient and/or dietary supplement, and as a sequestrant | U.S. FDA/EFSA | |
| Calcium citrate malate | (C6H7O7)x·(C4H5O5)y·(Ca2 +)z | 21–24 | 671 |
Soluble in water. 80 mmol/L |
Colorless or white; odorless | Rock‐derived. Calcium sourced from marble or limestone bound with citric acid and malic acid | Used as a general‐purpose food additive, as a nutrient and/or dietary supplement, and as a sequestrant | U.S. FDA/EFSA | |
| Calcium lactate | C6H10CaO6 | 13–18 | 218 | 0.13 mmol/L | White, neutral taste, almost odorless. Unpleasant taste if too concentrated | Rock‐derived. Calcium sourced from marble or limestone bound with lactic acid. Also found in foods like aged cheese | Preservative in foods and beverages; calcium replenisher | U.S. FDA/EFSA | |
| Calcium lactate gluconate | C9H16CaO10 | 12 | 324 |
Highly soluble. 1233 mmol/L |
White, crystalline, odorless, tasteless powder | Mixture of calcium gluconate and calcium lactate | Used for clear beverages and concentrated or instant preparations (baby food, infant formula, dairy, desserts, jams, and soy products), also as a pH adjuster and chelating agent | Powder; store in airtight plastic container at room temperature or refrigerator; easy to process; highly stable against phenols, tartrates, and CO2 | U.S. FDA/EFSA |
| Calcium ascorbate | CaC12H14O12 | 10 | 390 | Freely soluble in water; practically insoluble in methanol and ethanol | A white to slightly yellow crystalline powder; odorless | Rock‐derived. Calcium sourced from marble or limestone bound with ascorbic acid | Antioxidant/color fixative (prepared meat, dairy, and baby products) | U.S. FDA | |
| Calcium glycerol‐phosphate | C3H7CaO6P | 10 | 210 |
1 g in 50 mL of water at a lower temperature; insoluble in alcohol. 95.2 mmol/L |
Fine, white, odorless, almost tasteless powder | Glycerophosphoric acid | Used as a dietary supplement; and in food products such as gelatins, puddings, and fillings | Hygroscopic | U.S. FDA/EFSA |
| Calcium gluconate | C12H22CaO14 | 9 | 430 |
Slowly soluble in water; insoluble in organic solvents. 73.6 mmol/L |
Crystals, granules, or powder; white, bland taste or tasteless, odorless | Rock‐derived. Calcium sourced from marble or limestone bound with gluconic acid | Used in coffee powders to prevent caking, as a sequestering agent; food additive; as buffer; in vitamin tablets; a gelling agent in foods; sequestrant in foods | Stable in air. Loses water at 120 °C. Store below 40 °C. Protect from freezing | U.S. FDA/EFSA |
| Calcium glubionate | C18H34CaO20 | 7 | 611 |
Soluble in water, freely soluble in boiling water. 95.2 mmol/L |
White to yellow‐tinged white crystalline powder; almost tasteless, odorless | Used as a dietary supplement | Store in a well‐closed container at a temperature not exceeding 25 °C, protected from direct sunlight and moisture | ||
| Calcium stearate | C36H70CaO4 | 7 | 607 |
Slightly soluble in hot vegetable and mineral oils; quite soluble in hot pyridine; insoluble in alcohol and ether. 0.0007 mmol/L |
Fine, crystalline white to yellowish white bulky powder | Made from calcium chloride and sodium salts of mixed fatty acids (stearic and palmitic) | Used as a food additive; as conditioning agent; as an anticaking agent in dehydrated vegetable products, salt, and onion and garlic powder; to ensure tablet supplements do not stick in the machine | Decomposed by many acids and alkalis; when heated to decomposition, it emits acrid smoke and irritating fumes | U.S. FDA |
| Calcium propionate | C6H10CaO4 | NA | 186 | Soluble in water; slightly soluble in methanol and ethanol; practically insoluble in acetone and benzene | Powder or monoclinic crystals; white or colorless | Made from propionic acid + calcium hydroxide | Inhibitor of molds and other microorganisms in bread and other foods; for encapsulation in hydrogenated vegetable oil; in chemically leavened products | When heated to decomposition, it emits acrid smoke and irritating fumes | U.S. FDA |
| Calcium peroxide | CaO2 | NA | 72 | Slightly soluble in water; soluble in acids with formation of hydrogen peroxide | White or yellowish powder; white tetragonal crystals; odorless; almost tasteless | Made by the interaction of solution of a calcium salt and sodium peroxide with subsequent crystallization | Used in chewing gum; as dough conditioner in the United States but not in Europe; for cultivation of tomatoes, cucumbers, tobacco, and prawns in Japan; as a coating on beet seeds in Europe | Hygroscopic; decomposes in moist air; need to store in well‐closed container | U.S. FDA |
| Calcium caseinate | C81H125N22O39P | NA | Stable at a pH > 5.7. At a neutral or acidic pH, casein is relatively insoluble in water, and is easily separated from other milk proteins, sugars, and minerals. It is influenced by heat with temperatures as low as 50 °C (122 °F) | Appears as a milky liquid | Produced by changing the pH of milk to neutral or acid to become insoluble in water and isolate it from the other proteins in milk. It is then combined with calcium hydroxide at high alkaline levels and dries the protein | Used in the formation of emulsions in coffee whiteners, desserts, and whipped toppings; to produce sausage skins; to coat fruit and vegetable products for freshness | Very stable substance. It increases the shelf life, improves nutritional content, and enhances taste and smell | U.S. FDA | |
| Calcium iodate | Ca(IO3)2 | NA | 390 | Solubility in water: 0.10 g/100 mL. More soluble in aqueous solutions of iodides and amino acid solvent than in water | Monoclinic‐prismatic crystals; colorless; odorless | Prepared by passing chlorine into a hot solution of lime in which iodine has been dissolved | Used to improve properties of yeast‐leavened bakery products; nutritional source of iodine in foods and feedstuffs; as food additive, dough conditioner | Sensitive to reducing agents; decomposes on heating | U.S. FDA |
| Calcium pantothenate | C18H32CaN2O10 | NA | 259 | Very soluble in water, benzene, and ethyl ether | Yellow viscous oil | Calcium salt of the water‐soluble vitamin B5 | Skin conditioning agents | Unstable; easily destroyed by acids, bases, and heat. When heated to decomposition, it emits toxic vapors of nitric oxide | U.S. FDA |
| Calcium stearoyl‐2‐ lactylate | C48H86CaO12 | NA | 895 | Slightly soluble in hot water | White or slightly yellowish powder or brittle solid with a characteristic odor | Octadecanoic acid, 2‐(1‐carboxy‐ethoxy)‐1‐methyl‐2‐oxoethyl ester, calcium salt (2:1) | As dough strengthener or emulsifier; as surface active agent, emulsifier, or stabilizer in icings, fillings, puddings, and toppings, in liquid and solid edible fat‐water emulsion, snack dips, and cheese and cheese products, in sauces or gravies; as substitutes for milk and cream in coffee; as surface active agent in dehydrated potatoes | U.S. FDA |
a
Elemental calcium absorbed in the body.
b
Calcium carbonate can come in various forms for use as dietary supplements, such as dolomite, bone meal, and oyster shell.
In terms of calcium equivalents, which can be calculated by the amount of the calcium salt (mg cation + mg anion, or mL of a specified concentration) or the amount of elemental calcium (in mg, mEq, or mmol), these salts vary a little.
*Calcium has a valence of +2, so mEq = 2 × mmol.