Mellican Renée I, Li Jianjun, Mehansho Haile, Nielsen S Suzanne
The Procter & Gamble Company, Miami Valley Laboratories, 11810 East Miami River Road, Cincinnati, Ohio 45252, USA.
J Agric Food Chem. 2003 Apr 9;51(8):2304-16. doi: 10.1021/jf020681c.
Iron deficiency affects over two billion people worldwide (Lotfi, M.; Venkatesh Mannar, M. G.; Merx, R. J.; Naber-van den Heuvel, P. Micronutrient Fortification of Foods: Current Practices, Research,and Opportunities; Micronutrient Initiative: Ottawa, Ontario, Canada, 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 goal of this research was to examine the interaction of iron with simple phenolics and polyphenols. Factors that may affect off-color development, such as pH, oxygen, temperature, and reducing and chelating agents, were evaluated as a model for food products. Our 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. Because this is an oxidation/reduction reaction, the redox potential of all of the components is critical to the color development. Ferrous iron sources with low redox potentials and ferric iron sources with high redox potentials caused off-color development with catechol. Only polyphenols that contain ortho-hydroxyl groups cause off-color development with iron. All of the factors tested affect off-color development and redox potential of the system. Low pH, low oxygen, high temperature, and the presence of reducing and chelating agents inhibited off-color development. To confirm the model, foods that contained these polyphenols were evaluated for off-color development when iron was added. The foods tested reacted similarly to the models of polyphenols with iron. Off-color development was caused by oxidation-reduction interactions between ferric iron and polyphenols that contained ortho-dihydroxyl groups. Ferrous iron needed to be oxidized to participate in off-color development. In addition, methods identified in the models to prevent off-color development were effective in most of the food products examined. Using the ferrous form of iron and maintaining it in its reduced form by lowering pH, removing oxygen, and including reducing agents, it was possible to fortify foods with highly bioavailable iron.
缺铁影响着全球超过20亿人口（Lotfi, M.; Venkatesh Mannar, M. G.; Merx, R. J.; Naber-van den Heuvel, P. 《食品的微量营养素强化：当前实践、研究与机遇》; 微量营养素倡议组织：加拿大安大略省渥太华，1996年）。然而，用生物利用率高的铁强化食品在技术上具有挑战性，因为会出现变色、变味，维生素催化降解以及脂质氧化等问题。生物利用率高的铁在食品和饮料变色过程中所起的作用尚未得到充分理解。本研究的目的是考察铁与简单酚类和多酚类物质的相互作用。作为食品模型，评估了可能影响变色的因素，如pH值、氧气、温度以及还原剂和螯合剂。我们的结果表明，与简单酚类儿茶酚反应导致变色的铁必须处于氧化态，并且在儿茶酚存在下铁会被还原。由于这是一个氧化/还原反应，所有组分的氧化还原电位对颜色的形成至关重要。氧化还原电位低的亚铁源和氧化还原电位高的铁源都会与儿茶酚发生变色反应。只有含有邻位羟基的多酚会与铁发生变色反应。所有测试的因素都会影响体系的变色和氧化还原电位。低pH值、低氧气含量、高温以及还原剂和螯合剂的存在会抑制变色。为了验证该模型，对含有这些多酚的食品在添加铁时的变色情况进行了评估。测试的食品与多酚和铁的模型反应相似。变色是由三价铁与含有邻二羟基的多酚之间的氧化还原相互作用引起的。亚铁需要被氧化才能参与变色过程。此外，模型中确定的防止变色的方法在大多数检测的食品中都是有效的。使用亚铁形式的铁，并通过降低pH值、去除氧气和添加还原剂将其保持在还原态，就有可能用生物利用率高的铁强化食品。
