Comparative effects of soil and foliar iron and zinc fertilization on phenolic content, antioxidant activity and dietary fiber in wheat (Triticum aestivum L.).

The agronomic application of Fe and Zn-chelate fertilizers represents an approach for modifying wheat grain composition.
In this study, total phenolic compounds (TP), antioxidant capacity (CUPRAC) and crude fiber were determined in grain and flour of two Macedonian wheat varieties treated by soil, soil+foliar and foliar application of Fe and Zn fertilizers.
The bread wheat varieties (Triticum aestivum L.) “Treska” and “Radika” were grown under the same field conditions.
In whole grain samples, TP content ranged from 0.92 to 1.29 mg GAE g⁻¹ DW in “Treska” and from 0.94 to 1.23 mg GAE g⁻¹ DW in “Radika”. The highest TP value in “Treska” was obtained under soil Fe application (1.29 mg GAE g⁻¹ DW), while in “Radika” under combined soil+foliar Zn treatment (1.23 mg GAE g⁻¹ DW). In flour samples TP ranged from 0.76 to 0.92 mg GAE g⁻¹ DW in “Treska” and from 0.83 to 1.04 mg GAE g⁻¹ DW in “Radika”. CUPRAC values in whole grain varied from 3.32 to 5.48 mmol TE g⁻¹ DW in “Treska” and from 3.82 to 5.07 mmol TE g⁻¹ DW in “Radika”. In flour samples values ranged from 1.8 to 2.2 mmol TE g⁻¹ DW in “Treska” and from 1.75 to 2.25 mmol TE g⁻¹ DW in “Radika”. Crude fiber content in whole grain ranged from 2.49 to 3.44% in “Treska” and from 2.25 to 3.43% in “Radika”, while in flour it ranged from 0.70 to 1.07% and from 0.58 to 1.38%, respectively. Fe- and Zn-chelate fertilizers influenced TP content, antioxidant capacity and fiber distribution in wheat grain and flour.

Keywords: wheat, biofortification, iron fertilization, zinc fertilization, phenolic content, antioxidant activity