Effects of different roasting conditions on physical-chemical properties of Polish hazelnuts (Corylus avellana L. var. Kataloński)

•Different temperature/time roasting conditions were applied to hazelnuts.•The phenolic content increased in all roasted samples.•The hazelnuts roasted at 160 °C demonstrated a phenolic content 49.3% higher than ones roasted at 130 °C.•In all samples α-tocopherol was the predominant tocol.•In samples roasted at 130 °C and 160 °C were found 79 and 102 volatile compounds.

The influence of different roasting conditions on the physical-chemical (water activity, moisture, colour, volatile compounds, tocopherols, phenolic content) properties of Polish hazelnuts (cv. Kataloński) was determined. Nuts were roasted at specific temperature/time conditions: 130 °C/40 min, 130 °C/50 min, 130 °C/60 min, 160 °C/20 min, 160 °C/25 min, 160 °C/30 min. Hazelnuts roasted at 160 °C showed a darker colour and a lower water activity and moisture than samples roasted at 130 °C. Compared to raw hazelnuts, the phenolic content increased in all roasted samples, although with a more concentration in nuts roasted at 160 °C (2998.84 mg/100 g, 3429.52 mg/100 g and 2927.81 mg/100 g after 20, 25 and 30 min, respectively). The different roasting conditions led to several aroma modifications, in fact in raw hazelnuts were identified just only 22 compounds, whereas in samples roasted at 130 °C and 160 °C were found 79 and 102 volatile compounds, respectively.