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Adipate is the salt product of a reaction between adipic acid and a basic, or high pH, compound. A salt, in the chemical sense rather than the table salt meaning, is an ionic compound with no net charge that is formed when an acid reacts with a base. An ionic compound occurs when a positively charged ion bonds with a negatively charged ion. There are several forms of adipate with different compositions and uses. Examples include the plastic additives Bis(2-ethylhexyl) adipate (DEHA) and dioctyl adipate (DOA), and the food additives potassium adipate and sodium adipate.
Adipic acid, from which adipate arises, takes the form of a white powder that is typically manufactured rather than found in nature. Chemically, adipic acid belongs to the class of dicarboxylic acids, organic compounds that have two carboxylic acid functional groups. A compound is organic if it contains carbon. The chemical formula of adipic acid is (CH2)4(CO2H)2. As an acid, when it is added to water, it releases hydrogen ions, or charged hydrogen atoms, into the solution, giving it a lower pH and a sour taste.
In its capacity as a food additive, adipate serves as an acidity regulator, or a pH control agent. An acidity regulator is added to alter the acidity or basicity of a food. Each acidity regulator has an E number listing. Potassium adipate, which is the potassium salt formed from an adipic acid reaction, has the E number “E357” and sodium adipate, which is the sodium salt arising from an adipic acid reaction with a base, has the E number “E356.” These compounds lend a sour flavor to foods and may be used as a gelling agent.
DEHA is a plasticizer used in aircraft lubricants, plastic food wrap, and in hydraulic fluids. Hydraulic fluids are liquids that transmit power in hydraulic machinery such as the steering system in a car. A plasticizer is a compound that, once added, makes a substance more malleable. DEHA was once on the United States Environmental Protection Agency’s (EPA) list of toxic chemicals due to the belief that DEHA was a possible human carcinogen, or cancer causing substance. Though tests on mice have shown carcinogenicity, other tests have raised doubt as to whether the compound could cause cancer in humans, inciting the EPA to remove DEHA from its list of toxic chemicals.
Dioctyl adipate, which is often confused with DEHA, is also a plasticizer. DOA is a pale to clear, oily fluid often used as an ingredient in plastic food wrap, antiperspirants, and lubricants. This compound remains flexible under cold conditions, withstands heat fairly well, resists weathering to a fair extent, and has low viscosity. Chemically, DOA is an ester of adipic acid, implying that adipic acid was reacted with an alcohol compound to form DOA. Its formula is C22H42O4.