Optimization of hazelnut kernel drying in an infrared dryer with microwave pretreatment using response surface methodology

In this study, hazelnut kernels were dried in an infrared dryer with microwave pretreatment. To determine the optimization conditions of the hazelnut samples, response surface methodology and central composite design were used to investigate the effect of temperature levels (45, 65 and 85 ° C), infrared power levels (500, 1000 and 1500 W) and microwave power levels (270, 450 and 630 W) on drying of hazelnut kernels. The adequacy and accuracy of the fitted models (Lack of Fit and R2) were checked with analysis of variance (ANOVA). Response surfaces and contour plots were created to show the interaction between the independent and the response variables. Based on the experiments, the optimum conditions for the highest values of effective moisture diffusivity and L* (color index) and the lowest values of consumption energy, shrinkage and a*, b* (color indices) were determined at air temperature of 45°C, microwave power of 470.86 W and infrared power of 1316.72 W. The optimum values of the response variables affecting the effective moisture diffusivity, consumption energy, shrinkage, L*, a* and b* were obtained 2.35×10-9 m2 s-1, 2.65 kWh, 12.94%, 54.10, 14.97 and 16.70, respectively.