Effects of roasting on antioxidant status and phenolic profiles of commercial turkish hazelnut varieties (Corylus avellana L.)

The effect of roasting on antioxidant status and phenolic profiles of commercial Turkish hazelnut varieties was assessed. Samples were examined for their total phenolics, free phenolic acids, condensed tannins, and total antioxidant activity (ORAC). One phenolic acid (gallic acid) were positively identified in natural and roasted hazelnut varieties. Total phenolics among hazelnut varieties ranged from 177.6 to 727.5 mg gallic acid equivalent (GAE)/100 g, gallic acid from 0.16 to 0.87 mg/100 g, condensed tannins from 9.41 to 31.63 mg of catechin equivalents (CE)/g, and total antioxidant activity (ORAC) from 4020 to 11422 µmol trolox equivalent (TE)/ 100 g. Significant losses in total phenolics (around 66 per cent), free phenolic acids (around 59 per cent), condensed tannins (around 76 per cent), and total antioxidant activity (ORAC) (around 42 per cent) were noted when the hazelnuts were roasted. The present work suggests that roasting resulted in significant loss in total phenolics, free phenolic acids, condensed tannins, and antioxidant activity (ORAC) due to the removal of the brown skin. It is suggested to consume hazelnut with its brown skin to benefit from natural functional properties.