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Novel strategies limit color changes in iron-fortified food products.

Iron, vitamin A, zinc and iodine have been recognized to be the micronutrients with the largest deficiencies among populations worldwide. Iron is highly reactive and may lead to negatively perceived organoleptic changes in products, such as dull color and off-taste.

But enriching foods with vitamins and minerals is one of the most productive and cost-effective ways to prevent hunger globally. For example, fortifying complementary infant food, including vegetable or fruit purees, can deliver the right amount of micronutrients to needy populations.

However, for vegetable and fruit purees, iron fortification often modifies the products' color and taste. These changes to color and taste, which are caused by the high amount of polyphenols in fruit purees which react with iron, can negatively affect acceptance of the products by consumers who often focus on product color as a key freshness indicator.

Scientists at Nestle indicate that usually the way to keep this from happening is to use poorly soluble iron compounds. Although this might improve color stability, it often has a negative impact on the bioavailability of the nutrients.

To find a solution to this problem, the researchers utilized a model system based on polyphenols involved in color changes with ferrous sulphate. They examined the role of pH, polyphenol concentration, heat treatment and stability constants in samples fortified with iron. The resulting data could guide them in identifying approaches that would limit the negative effects that occur when added iron reacts with polyphenols in foods to form iron-polyphenol complexes.

Specifically, phenolic compounds with two or more vicinal hydroxy benzyl moieties in their structure, such as catechols and pyrogallols, were examined for their ability to give spectral bathochromic shift phenomena when mixed with iron salts.

Strategies for limiting color development were based on: adjusting the pH; the saturation of polyphenols with unreactive divalent metal ions; and the suppression of iron reactivity through complexation. Some of these strategies resulted in a significant improvement in color stability, with the best results achieved by the latter.

The findings in model systems gave good insight of the mechanisms involved in color changes. The Nestle researchers were able to apply the findings to iron-fortified banana puree.

Further information. Nicola Galaffu, Micronutrient Fortification Group, Nestle Research Centre, Vers-chez-les-Blanc, PO Box 44, CH-1000 Lausanne 26, Switzerland; phone: +41 21 785 81 11; email:

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Author:Galaffu, Nicola
Publication:Emerging Food R&D Report
Date:Jul 1, 2016
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