Along with the practice of applying micronutrients to leaves that ultimately end up in the food product, techniques in milling grains and the baking process, all had much influence on the food’s iron and zinc (Fe and Zn) content.
Furthermore, variable responses found in wheat varieties was another consideration that the Italian team said “should be considered when introducing agronomic biofortification in planning breeding strategies that to improve mineral content in grain.”
“These results are of great support for developing a production chain of bread enriched with health-promoting compounds and bioavailable minerals and with potential protective roles against chronic cardio-vascular diseases,” they added.
The World Health Organization (WHO) identifies over 2 billion people as being deficient in key micronutrients such as Fe and Zn.
Several potential biofortification strategies are in place that attempt to increase the concentrations of Fe and Zn in cereals.
These include conventional breeding and genetic engineering as well as crop fertilization.
Soil and foliar (leaf) Fe fertilization appear to be less effective than Zn fertilization in increasing mineral concentrations in bread wheat grain, as Fe is converted to an unavailable form when applied to soils.
Researchers from the Sant’Anna School of Advanced Studies in Pisa, Italy began looking at wholemeal flour of two common wheat varieties Gentil Rosso (old) and Blasco (modern).
Two biofortification treatments (biofortification with Fe and Zn and the control) were then applied to each wheat variety.
Twelve loaves were then prepared from the wholemeal flour of the four treatments and three loves were prepared using the white flour (non-biofortified) modern variety.
In addition, the effect of milling and bread making techniques were also noted.
Biofortification increased the concentration of Zn (+78%) and its bioavailability (+48%) in the flour of the old variety, whereas it was ineffective in increasing Fe concentration in both varieties.
However, the old variety showed higher concentration (+41%) and bioavailability (+26%) of Fe than the modern one.
As regards milling, wholemeal flour had higher Fe, Zn concentration and health-promoting compounds compared to white flour.
Bread making slightly altered Fe and Zn concentration but greatly increased their bioavailability (77 and 70%, respectively).
“Foliar biofortification with Fe and Zn greatly increased concentration and bioavailability of Zn only in the flour of the old variety of wheat, whereas it was ineffective on the Fe concentration in both varieties,” the study identified.
“However, the old variety had higher concentration and bioavailability of Fe than the modern one.”
The team also found that the milling technique was a significant factor in the nutritional and nutraceutical profile of wheat flour, since Fe, Zn and their bioavailability as well as polyphenols, flavonoids, and antioxidant activity were higher in the wholemeal flour than in the white flour.
Additionally, the nutritional and nutraceutical properties of wholemeal flour were preserved in bread.
The team also noted that foliar Fe and Zn biofortification did not affect total polyphenol and flavonoid amounts and antioxidant activity in wholemeal flour.
Biofortification with Zn has previously been shown to increase the accumulation of total phenols and flavonoids in the berries of common grape vine (Vitis vinifera L.) and in cabbage (Brassica oleracea L).
“Our results showed differences in antioxidant activity between the old and the modern variety of bread wheat but not in the total polyphenols and flavonoids,” the study remarked.
The higher antioxidant activity observed in the old variety compared to the modern one is in contrast with the results of a previous study that showed modern bread wheat varieties to have a higher antioxidant activity than old ones.
Source: Journal of Agriculture and Food Chemistry.
Published online ahead of print: DOI: 10.1021/acs.jafc.7b01176
“Biofortification with Iron and Zinc Improves Nutritional and Nutraceutical Properties of Common Wheat Flour and Bread.”
Authors: Valentina Ciccolini et al.