The target of this work was to investigate the influence of microwave pretreatments (at five levels of 0, 30, 60, 90, and 120 s) on the total phenolics content, antioxidant potential, mass transfer rate, effective moisture diffusivity (D eff), and rehydration rate of sweet cherries (SC). The drying duration of microwave-treated SC was shorter than the untreated sample. The average drying time of fresh SC microwaved for 0, 30, 60, 90, and 120 s were 220, 205, 190, 175, and 150 min, respectively. The D eff values, total phenolics, and antioxidant capacity of microwave-treated SC were higher than the untreated sample. In this study, the SC D eff as determined by the second Fick law varied from 8.73 × 10-10 to 1.41 × 10-9 m2/s. The experimental data for the dehydration curves were fitted to different thin-layer equations, and the Midilli equation using the experimental constants best described the drying rate of SC. As the microwave pretreatment time increased from 0 to 120 s, the total phenolics and antioxidant capacity of dried SC increased from 1491.4 μg Gallic acid equivalents (GAE)/g dry to 2272.1 μg GAE/g dry, and 54.47%-62.59% (p < .05). The microwave pretreatment enhanced the rehydration rate of dried SC. The rehydration percent of dried SC microwaved for 0, 30, 60, 90, and 120 s were 127.27%, 136.63%, 136.91%, 137.07%, and 136.72%, respectively.
Keywords: Fick law; Gallic acid equivalents; Midilli equation; antioxidant capacity; total phenolics content.
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