Disodium pyrophosphate or sodium acid pyrophosphate (SAPP) is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

. It consists of

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

cations An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

() and dihydrogen pyrophosphate

anions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

(). It is a white, water-soluble solid that serves as a buffering and

chelating agent Chelation () is a type of bonding of ions and their molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These l ...

, with many applications in the food industry. When crystallized from water, it forms a hexahydrate, but it dehydrates above room temperature. Pyrophosphate is a polyvalent anion with a high affinity for polyvalent cations, e.g. . Disodium pyrophosphate is produced by heating sodium dihydrogen phosphate: :

Food uses

Disodium pyrophosphate is a popular

leavening agent In cooking, a leavening agent () or raising agent, also called a leaven () or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An altern ...

found in

baking powder Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a buffer such as cornstarch. Baking powder is used to increas ...

s. It combines with sodium bicarbonate to release carbon dioxide: : It is available in a variety of grades that affect the speed of its action. Because the resulting phosphate residue has an off-taste, SAPP is usually used in very sweet cakes which mask the off-taste. Disodium pyrophosphate and other sodium and potassium polyphosphates are widely used in food processing; in the

E number E numbers, short for Europe numbers, are codes for substances used as food additives, including those found naturally in many foods, such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...

scheme, they are collectively designated as E450, with the disodium form designated as E450(a). In the United States, it is classified as

generally recognized as safe Generally recognized as safe (GRAS) is a United States Food and Drug Administration (FDA) designation that a chemical or substance added to food is considered safe by experts under the conditions of its intended use. An ingredient with a GRAS d ...

(GRAS) for food use. In canned seafood, it is used to maintain color and reduce purge during retorting. Retorting achieves microbial stability with heat. It is an acid source for reaction with baking soda to leaven baked goods. In baking powder, it is often labeled as food additive E450. In

cured meat Curing is any of various food preservation and flavoring processes of foods such as meat, fish and vegetables, by the addition of salt, with the aim of drawing moisture out of the food by the process of osmosis. Because curing increases the solu ...

s, it speeds the conversion of

sodium nitrite Sodium nitrite is an inorganic compound with the chemical formula . It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite sa ...

nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

() by forming the

nitrous acid Nitrous acid (molecular formula ) is a weak and monoprotic acid known only in solution, in the gas phase, and in the form of nitrite () salts. It was discovered by Carl Wilhelm Scheele, who called it " phlogisticated acid of niter". Nitrous ac ...

(HONO) intermediate, and can improve water-holding capacity. Disodium pyrophosphate is also found in frozen

hash brown Hash browns, also spelled hashed browns and hashbrowns, are a List of American breakfast foods, popular American breakfast food consisting of finely Julienning, julienned potatoes that have been fried until golden Food browning, brown. Hash brown ...

s and other

potato The potato () is a starchy tuberous vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are underground stem tubers of the plant ''Solanum tuberosum'', a perennial in the nightshade famil ...

products, where it is used to keep the color of the potatoes from darkening. Disodium pyrophosphate can leave a slightly bitter aftertaste in some products, but "the SAPP taste can be masked by using sufficient baking soda and by adding a source of calcium ions, sugar, or flavorings."

Other uses

leather Leather is a strong, flexible and durable material obtained from the tanning (leather), tanning, or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from cattle, sheep, goats, equine animals, buffal ...

treatment, it can be used to remove

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

stains on hides during processing. It can stabilize

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

solutions against reduction. It can be used with

sulfamic acid Sulfamic acid, also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, sulphamic acid and sulfamidic acid, is a molecular compound with the formula H3NSO3. This colourless, water-soluble compound finds many applications. Sulfamic ...

in some dairy applications for cleaning, especially to remove soapstone. When added to scalding water, it facilitates removal of hair and scurf in hog slaughter and feathers and scurf in poultry slaughter. In petroleum production, it can be used as a

dispersant A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid (such as a colloid or emulsion) to improve the separation of the particles and to prevent their sett ...

in oil well drilling muds. It is used in

cat food Cat food is food specifically formulated and designed for consumption by cats. During the 19th and early 20th centuries, cats in London were often fed horse meat sold by traders known as Cats’ Meat Men or Women, who traveled designated routes ...

s as a

palatability Palatability (or palatableness) is the hedonic reward (which is pleasure of taste in this case) provided by foods or drinks that are agreeable to the "palate", which often varies relative to the homeostatic satisfaction of nutritional and/or wa ...

additive. Disodium pyrophosphate is used as a tartar control agent in toothpastes.

References

External links

* {{Phosphates Pyrophosphate salts Sodium compounds Edible thickening agents