Influence of Drying Conditions and Temperature on Hazelnuts (Corylus avellana) Fruit Quality

Hazelnut fruit or kernel has nutritional and medicinal value and is consumed raw or roasted. Used hazelnut was Gerd-e-Eshkevarat. To determine the best drying temperature for hazelnuts, a factorial experiment in a completely randomized design with two factors; dryer air temperature in three levels (40, 50 and 60°C) and fruit type in two levels (with and without skin) in three replications was applied. Fruits were dried in a thin layer with a laboratory dryer. To determine the specialized energy required for drying hazelnut in each treatment, electrical work equation in dryer (heater work + fan work) was used. Peroxide and acidity of hazelnut oil were measured by standard institute and Iran industrial research methods. The results showed that the interaction effect of fruit type and temperature was not significant on fruit oil percentage, but other traits were influenced by interaction effect of treatments. The highest percentage of protein (13.62%) was obtained in roasted hazelnuts with 60°C and with skin. The highest and lowest percentage of oil acidity (0.28 and 0.11%) were recorded in roasted hazelnuts with 50°C with and without skin, respectively. Peroxide numeral value (8.25 and 1.30) was obtained in roasted hazelnuts with 40 and 60°C with skin, respectively. Overall, 60°C was the most suitable temperature for drying hazelnut fruit which resulted to enhance most physiologic and taste traits.