The flavor problem of soybean oil. XII. Nitrogen coordination compounds effective in edible oil stabilization

Summary Metal deactivating agents containing nitrogen as the coordinating atom have been developed for use in edible oils. The most effective compounds were those containing two carboxyl groups, α,α′ to the nitrogen. Those containing β,β′ carboxyls were less effective, and the efficiency of α,β carboxyls was intermediate. The activity is explained on the basis of the formation of metal chelation rings—complexes believed to be typical Werner's coordination complexes. The nitrogen atom may be an amine or a cyclic nitrogen. Complex coordination compounds can also be formed from acidic nitrogen compounds, such as hydroxamic acids, when the proper structure for metal chelation exists. Chelidamic acid has been found to be a very efficient metal deactivating agent for both copper and iron. Imino α or β dicarboxylic acids show varying degrees of effectiveness toward the complexing of iron and copper. The greater the number of 5‐membered chelation rings that are possible around the metal atom, the greater is the observed stability.