DRYING KINETICS AND MOISTURE TRANSFER PARAMETERS OF HAZELNUT

Abstract

In this experimental study, drying kinetics, sorption isotherms and mass transfer parameters (mainly the diffusion coefficient and hm) of hazelnut are investigated under various drying air conditions. Experiments were conducted in a lab-scale convective drier under the following drying conditions: temperatures at 25C, 35C, 45C and 55C; velocities at 0.3, 0.6 and 0.9 m/s; relative humidity values at 20%, 40%, 60% and 80%. Initially, sorption isotherms of the dried hazelnut are determined for different temperatures and equilibrium relative humidity values. Then, the drying characteristics of hazelnut are determined for various values of drying air parameters tested. In addition, the mass transfer parameters (i.e., Bi, moisture diffusion coefficient and hm) of hazelnut were evaluated using a correlation. The Bi numbers were in the range 0.4216–1.4806 and moisture diffusion coefficient and hms in the range from 0.7056 × 10−9 to 3.2933 × 10−9 and from 1.2401 × 10−7 to 1.7361 × 10−7 m/s, respectively. PRACTICAL APPLICATIONS Turkey is the largest hazelnut-producing country, providing most of world hazelnut production. Supplying the market with the best product available is always critical. Therefore, ensuring better harvesting and processing conditions of hazelnut attracts a great deal of research interest. To prevent field losses by unfavorable weather conditions, there is a tendency to harvest hazelnuts at moisture contents above safe storage levels. In this regard, drying seems to be necessary.