Nutritional composition and antioxidant activity in hazelnut shells from US-grown cultivars

The hard shell of a hazelnut is a major waste of the hazelnut industry. The chemical composition, phenolic compounds (total phenolics, tannins and condensed tannins), antioxidant activity (DPPH and ABTS free-radical scavenging assays), and the relationships between phenolic compounds and antioxidant activities of the hazelnut shells from twelve US grown cultivars were investigated to for potential commercial development. Crude fibre accounted for over 85% of total carbohydrate. The shells contained high concentrations of phenolic compounds. Concentrations of phenolic constituents and ABTS+ -scavenging capacities were significantly higher (P > 0.05) in the Oregon cultivars than their Nebraska counterparts. There were significant positive correlations between ABTS+ scavenging capacities and the phenolic compounds, whereas DPPH -scavenging capacity demonstrated a weak negative correlation with ABTS+ scavenging capacity and the phenolics. The results suggest that hazelnut hard shell may serve as a potential source of natural antioxidants for food applications.