The interaction of iron with polyphenols
Abstract
Iron deficiency affects over two billion people worldwide (Lotfi et al., 1996). However, fortifying foods with highly bioavailable iron is technically challenging because of off-color and off-flavor development, catalytic degradation of vitamins and oxidation of lipids. The role of highly bioavailable iron in the off-color development of foods and beverages is not well understood. The goals of this research included: (1) determining the role of iron in off-color development with simple phenolics and polyphenols as models for more complex systems, (2) evaluating the effect of environmental factors, such as pH, temperature, oxygen, redox potential, reducing agents, and chelating agents, on off-color development, and (3) validating these models in commercial food products. The results demonstrated that the iron that reacts with the simple phenolic, catechol, to develop off-color must be in the oxidized state, and the iron is reduced in the presence of catechol. Iron sources that are typically used for fortification, as well as other metals, were evaluated for off-color development with catechol versus redox potential. Ferrous iron sources with low redox potentials, and ferric iron sources with high redox potentials, caused off-color development with catechol. In addition, only polyphenols that contain ortho-hydroxyl groups caused off-color development with iron. Off-color development was minimized by factors such as low pH, low oxygen content, high temperature, and presence of reducing and chelating agents. All of these factors affected the redox potential of the system. Therefore, the interaction of iron with polyphenols was an oxidation/reduction reaction, where iron was reduced and the polyphenol was oxidized. The off-color development was controlled by the redox potential of the compounds in the system. The commercial foods tested reacted similarly to the models of polyphenols with iron, and methods identified in the models to prevent off-color development were effective in most of the food products examined, suggesting that the proposed models are valid for testing commercial products.
Degree
Ph.D.
Advisors
Nielsen, Purdue University.
Subject Area
Food science|Nutrition
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