Effect of supplementary irrigation on total antioxidant capacity and phenolic content of hazelnut

Abstract

Aim of this study was to investigate the effect of supplementary irrigation on the total antioxidative capacity and total phenolic content of hazelnuts. Orchard of hazelnut trees were irrigated at the different growth stages combinations. To determine antioxidative capacity, the samples were analyzed by the spectrophotometric assay using the stable DPPH radical. The total phenolic content was determined by the Folin-Ciocalteu assay. The results indicated that the total antioxidative capacity was affected by the irrigation conditions. The hazelnut kernels and defatted hazelnut kernels from irrigated at all growth stages showed the highest antioxidative capacity, while the lowest antioxidative activity was observed in control (no irrigation applied). On the contrary, the hazelnut kernel oil obtained from control induced higher antioxidative capacity than irrigated at the first growth stage. These spectrophotometrically measurements confirm that hazelnut kernels and their oils contain antioxidative components having different structural properties such as lipophilic and hydrophilic character and amounts of these compounds were changed by irrigation conditions. In contrast, any notable change of total phenolic content was observed in hazelnut samples, depending on the irrigation condition.