Cereal Chem 64:256-259   |  VIEW ARTICLE

Changes in Iron Forms During Extrusion Processing.

R. S. Kadan and G. M. Ziegler, Jr. Copyright 1987 by the American Association of Cereal Chemists, Inc. 

Cereal mixes consisting of corn meal, rice flour, and soy protein isolate were fortified with three iron sources (FeSO4, Fe2O3, and electrolytic iron [EI]), ascorbic acid, citric acid, and an antioxidant, butylated hydroxyanisole, in various combinations. Each mix was extruded to produce a simulated breakfast/snack food. Analysis of the extruded food for metallic, soluble, and complexed iron in aqueous slurry and under simulated stomach digestion conditions was performed. Metallic iron was subjected to electron spectroscopy for chemical analysis (ESCA). Results showed that for FeSO4 and EI an extruded food contained more soluble iron under simulated stomach conditions than an unextruded mix. In aqueous slurries, nearly all iron from FeSO4 and Fe2O3 and about three-fifths of the EI had complexed with the mix during extrusion. The addition of organic acids and antioxidant to the mix containing FeSO4 and EI increased soluble iron under simulated stomach conditions. The addition of Fe2O3 to the mix with or without additives did not appreciably increase soluble iron under simulated stomach conditions. As expected, most of the soluble iron was in the ferric form in aqueous slurries and in the ferrous form in simulated stomach conditions. ESCA studies confirmed that when atmospheric oxygen was present during processing, the exterior of electrolytic iron particles was susceptible to oxidation to ferric form. The ESCA data further indicated that the outer layer of starting EI, as well as the metallic iron recovered from extruded foods and iron rust, had similar oxidation states, as shown by binding energies for iron and oxygen.