The Greek origin of the word chelate signifies the plier-like claws of a crab, thus depicting the concept of clinging or holding with a strong grip. The term chelate was first applied by Sir Gilbert T. Morgan and H. D. K. Drew in 1920. They suggested the term for the caliper-like groups which function as two associating units and fasten to a central atom so as to produce heterocyclic rings.
Free metal ions in food systems may form insoluble or colored compounds or catalyze degradation of food components, resulting in precipitation, discoloration, rancidity or loss of nutritional quality.
Chelating agents eliminate these undesirable effects by forming stable, usually water-soluble complexes with free metal ions. A chelate is a water-soluble complex between a metal ion and a complexing agent. It usually does not dissociate easily in solution, but forms an inert complex. In labile complexes, however, the metal ion can be readily exchanged.
Chelating agents such as malic acid, citric acid and tartaric acid are used to prevent the flavor changes, discoloration and rancidity of the foods. These are very important in food manufacturing companies.
Chelating agents have a ring-like center which forms at least two bonds with the metal ion allowing it to be excreted. Chelating agents are usually organic compounds (a compound that contains carbon) which have high affinity and can bind/carry metal ions and play very important roles in living systems e.g., hemoglobin, transferrin, phytochelators and microbial siderophores.
The combination of surface active and chelating properties in a single molecule result in a chelating surfactant. These are water soluble molecules suitable for chelation in most aqueous systems.
Chelating agents serve as scavengers of metals which catalyze oxidation. For example, EDTA is a chelating agent permitted for use in the food industry as a chemical preservative. Calcium disodium EDTA and disodium EDTA have been approved for use as food additives by the United States Food and Drug Administration.
In beverages, chelating agent prevents flavor and color degradation in soft drinks and fruit drinks. This is a particular problem with certified colors and when any ascorbic acid is present.
Trace quantities of metal ions are naturally present in most vegetable products. During processing and retort, trace amounts of iron are released and available to form highly colored salts. Natural color of the canned products can be maintained by the use of chelating agents.
Food additive - Metal chelator
