Iron bioavailability of fortified skim milk: An in-vitro study to investigate the influence of iron salt fortification on the phase distribution and oxidation state of iron in skim milk

Anaemia affects a third of women and almost 50% of infants and toddlers worldwide. Iron deficiency is the most common cause of anaemia, and the most common nutritional disorder in the world. To increase dietary iron intake, iron fortification of staple foods commonly consumed by the general public is an effective approach to prevent and control iron deficiency anaemia. It is important to maximise the iron bioavailability (absorption by the human body) in these fortified products, since iron overload is also known to cause Since the diet of infants and toddlers revolves around milk, milk is a good food carrier to address iron deficiency anaemia in children. The aim of this project is to assess the influence of five factors on the bioavailability of iron fortified skim milk: (1) iron concentration, (2) molecular form of the added iron, (3) storage time after fortification, (4) the addition of an iron enhancer and (5) the addition of an iron inhibitor.Skim milk was fortified with FeC l2 and FeC l3 to 5 and 20 mmol Fe L−1and stored for 24 hours or one week.Part of the milk was further left untreated and to another part ascorbic acid (vitamin C) or tannic acid were added as respectively iron enhancer and iron inhibitor. The bioavailability of the iron in these milk samples was assessed on phase distribution and oxidation state, since it is believed that iron in the soluble phase of the milk and in the oxidation state Fe2+ is more bioavailable.Analysis showed that the difference in iron concentration induced a pH decrease, which was greater for the higher concentrations of iron and the molecular form FeC l3. The pH difference caused the percentage of iron present in the casein fraction to increase, in the protein fraction to decrease and did not influence the iron in the soluble phase. It was also found that the 20 mmol L −1 FeC l2 showed more iron in the soluble phase and more Fe2+, whereas no statistical difference was observed for the 5 mmol L −1 , which might also be dueto the pH difference. The increase in storage time to one week was reflected by an increase in iron bound to the caseins. This shift was not reflected in a change of oxidation state. The addition of the iron enhancer (ascorbic acid) increased the iron present in the protein fraction and soluble phase, which was strengthened by the further decrease in pH. The chelation of iron by ascorbic acid did not necessarily reduce Fe3+ tot Fe2+; the Fe2+ decreased for the 20 mmol L −1 FeC l2, whereas it increased for the 20 mmol L −1 FeC l3. Lastly theaddition of the iron inhibitor resulted in a significant decrease of Fe2+. Most iron was bound to the casein or precipitated as iron-tannic acid complex.Overall, this research confirmed that the bioavailability of milk is not easily evaluated, since the behaviour of iron in milk depends on many different factors that can not be studied isolated. Only by evaluating many possible combinations of concentration, molecular forms, additives and storage conditions, the bigger puzzle can be solved. This project attributed to a part of the solution and is therefore a valuable contribution in the development of bioavailable milk products, that will reduce iron deficiency anaemia in children.Applied Physic