Nano iron could lead to big fortification future

Using a technique called flame spray pyrolysis, researchers from the Swiss Federal Institute of Technology; Zurich (ETH) have prepared nano-structured iron and zinc complexes with improved bioavailability, which could offer opportunities to tackle two of the globe’s major deficiency concerns.

Florentine Hilty told attendees at the IFT International Food Nanoscience Conference at the Hilton in Anaheim that early development work of the nano-structured complexes showed that feeding iron-deplete rats resulted in approximately the same bioavailability as that observed for iron sulphate, the so-called gold standard for iron.

Iron deficiency affects about a third of the global population, with two billion people anaemic around the world, said Hilty. In addition, zinc deficiency affects 30 per cent of the world’s population.

Two main avenues are open to redress the balance in favour of iron and zinc status, she said, and these are supplementation and fortification. “Fortification is the most cost-effective and you can reach a large population,”​ said Hilty.

The research is still in its early stage, she said, and preliminary safety data indicated no adverse side effects, no histological abnormalities in the animals, and no elevation of oxidative stress, as measured by TBARS. Hilty stressed however that the studies to date were from a short feeding period and that they were not toxicological studies.

Iron challenges​

Fortification of foods with iron poses several challenges, depending on the types of iron used. Using water-soluble iron sulphate or iron gluconate offer the advantages of providing high bioavailability, but the disadvantage of adversely affecting the colour of the resultant product. On the other hand, water- insoluble elemental iron or ferric phosphate offer poor bioavailability.

“With nano, the bioavailability of elemental iron in rats can increase with increasing surface area,”​ Hilty told attendees in Anaheim. “The nano-structured complexes also lower the impact on certain food matrices.”​

The flame spray pyrolysis technique appears to offer a viable method of producing cheap and bioavailable nano-scale complexes for iron and zinc fortification, said Hilty. The technique works by forming nano compounds when a precursor is sprayed into a flame with oxygen. The nano complex is then collected in a filter. The technique is versatile, can produce atomically mixed compounds with a high surface area, and is cheap with high production rates.

“We need to be cost-effective, especially if we want to go into fortification of staple foods in developing countries,”​ she said.

The Swiss researchers have produced complexes with different ratios of iron and zinc, while phosphate inclusion can improve the solubility of the iron-zinc. Furthermore, other minerals such as calcium and magnesium can be added, said Hilty, without affecting the solubility of the iron and/or zinc.

Bioavailability results from in vitro​ and in vivo​ tests showed that, compared to iron sulphate, the bioavailability of iron-zinc phosphate was 95 per cent, iron-zinc-magnesium oxide was about 91 per cent, and iron-zinc-calcium oxide was about 82 per cent.

Despite promising early data, Hilty cautioned that future studies would include a complete safety evaluation, investigation of how the nano-structured compounds behave during different processes, such as extrusion, and storage studies to examine the effects of long term storage.

When quizzed on the effects of the nano-structure compounds on flavour and taste, Hilty added that no data is currently available on how they affect the sensory profile. Also, how the large surface area complexes affect oxidation is also currently unknown.