Effect of drying methods on nut quality of hazelnuts (Corylus avellana L.)

This study was conducted to determine the effects of hazelnut drying machine (DM₁ and DM₂; at 45 °C and 50 °C, respectively) and sun-drying (concrete ground and grass ground) methods on the chemical properties of Tombul, Palaz, and Ordu Levant hazelnuts. For this purpose, protein, lipid and moisture content, water activity, free fatty acid (FFA), peroxide value (PV), rancimat value (RV) and fatty acid composition were analyzed. As expected, it was observed that monounsaturated fatty acid (MUFA) was the main fatty acid group (81.58-84.80%) followed by polyunsaturated (PUFA; 9.53-11.42%) and saturated fatty acids (SFA; 5.87-6.92%), and the major group constituted ~ 99.00% of the total fatty acids, whereas the minor group constituted ~ 0.5% of these acids. However, caproic (C6: 0), caprylic (C8: 0), capric (C10: 0), lauric (C12: 0), eicosadienoic (20: 2), erucic (22: 1), docosadienoic (22: 2), and lignoceric (C24: 0) fatty acids were below limit of detection (< 0.001%). Samples dried in DM₁ and DM₂ had more MUFA (84.49%, 84.80, respectively), and lower SFA and PUFA than those using sun-drying methods. Following the drying process, the lowest FFA and PV (0.04-0.17%, 0.00-0.27 meq O₂ kg^-1, respectively) and the highest RV (5.46-6.05 h) were recorded in the DM₁ method. Furthermore, it was also observed that as the heat increased (DM₁ and DM₂; 45-50 °C, respectively), oleic/linoleic acidity ratio, FFA, and PV increased and iodine value and RV decreased. Therefore, DM₁ was thought to be a promising method for hazelnut drying.