Published in Food Research International, the research tested a variety of strategies to limit the effects of iron reactivity on colour changes in fortified foods – finding a number of approaches can help reduce undesirable changes to colour and flavour resulting from the addition of iron.
Enrichment of food with vitamins and minerals has been identified by several organisations, including the World Health Organisation (WHO), as one of the most efficacious and cost-effective means to prevent hidden hunger at global level, said the Nestlé team.
They noted the fortification of complementary infant food, including vegetable or fruit purees, can provide “a great contribution to deliver the right amount of micronutrients.”
“[However], for vegetable and fruit purees, iron fortification often leads to strong colour and taste modification,” said the team, led by senior author Nicola Galaffu from the Micronutrient Fortification Group at Nestlé Research Centre.
Such alterations to colour and taste, which are caused by the high amount of polyphenols in fruit purees reacting with iron, can lead to a reduction in consumer acceptance because they typically use colour as a key freshness indicator.
“The general approach to avoid this phenomenon is to use poorly soluble iron compounds. Although this might improve colour stability, it often has a negative impact on bioavailability,” wrote the team – adding strategies based on complexation generally lead to more stable and bioavailable solutions with less or no impact on colour and taste.
The Nestlé research team used a model systems approach based on polyphenols involved in colour changes with ferrous sulphate.
They tested the role of pH, polyphenol concentration, heat treatment and stability constants in food samples fortified with iron to help provide a guide in identifying promising strategies to limit the negative effects seen when ‘added iron’ reacts to polyphenols in foods to form iron-polyphenol complexes.
“The use of well accepted food ingredients was found to be a feasible approach for the stabilisation of highly reactive iron salts such as Ferrous Sulphate,” said Galaffu and her colleagues.
“Indeed, it was demonstrated how the influence of pH, complexation of iron to natural ligands, such as citrate, and competitive binding of other divalent micronutrients (such as magnesium, calcium and zinc) to polyphenols can be used to minimise undesired colour changes in the food product.”
They added that in the future it may be worthwhile for the industry to further develop strategies for limiting colour changes by extending the list of chelating food ingredients and/or testing combinations of existing strategies.
“Finally, the last step in the development of these strategies need also to take into consideration the iron absorption through clinical trials to ensure that during the reformulation a good bioavailability is also maintained,” the Nestlé team concluded.
Source: Food Research International
Published online ahead of print, doi: 10.1016/j.foodres.2016.05.017
“Strategies to limit colour changes when fortifying food products with iron”
Authors: Edwin Habeych, et al