Drying behavior and quality assessment of nectarine slices dried by different drying methods

In this study, nectarines were dried using four methods: microwave, hot air, microwave-hot air combination, and freeze drying. The effects of these methods were evaluated based on drying time, moisture diffusion, modeling, color, rehydration, energy use, and surface temperature. Two different microwave power values (200 and 300 W) and a single temperature value (50 °C) were used for product drying. The relation of the length of drying time of nectarine samples according to the methods was found as Freeze-dry>hot air>microwave>microwave-hot air. While the lowest effective moisture diffusion coefficient was obtained in freeze dry method, the highest effective moisture diffusion coefficient was found in 300 W-50 °C application. Midilli et al. model could be chosen to represent the thin-layer drying of nectarine slices for all cases. The greatest total color change (∆E) was observed in samples dried at 300 W-50 °C, whereas the minimal color change was recorded in the freeze-dried samples. Both rehydration capacity values (3.152±0.053) and energy consumption (4.152±0.215) values of freeze dried samples were found to be higher than the other methods. The highest product surface temperatures were found in products dried by microwave method. The study indicates that microwave–hot air drying offers shorter drying time with acceptable quality, while freeze drying, though less energy-efficient, provides superior quality.