In this study, the effects of air temperature (19.6 ℃, 32.8 ℃, 54.2 ℃, 64.3 ℃, and 82.9 ℃) on the microwave-convective coupled heating, drying characteristics, microwave output spectrum, and quality of the diced apples were investigated, and the comparisons among the single microwave drying, air drying, and microwave-convective coupled drying were done.Results showed that under the highest material temperature (80 ℃), the air temperature had a significant effect on the material temperature, drying time, and product quality.With the rise of air temperature, the mean temperature that the material could reach was higher, the heating uniformity was better, the drying time was shorter, and the moisture ratio of apple cubes showed an exponential downward trend.Compared with microwave drying and air drying, coupled drying could shorten the drying time by up to 50% and 62.2%, respectively.When the air temperature was lower than 82.9 ℃, the microwave worked in an uneven intermittent mode, and when the air temperature was 82.9 ℃, the drying proceeded in the segmented heating mode.Weibull distribution function and the Dincer model could accurately describe the drying process of diced apples.The shape parameter β indicated that drying was dominated by internal moisture diffusion control.The Biot number Bi indicated that the material temperature change during drying was governed by internal heat conduction.The estimated moisture diffusivity Dcal ranged from 2.40×10-7 m2/s to 4.43×10-7 m2/s while the effective moisture diffusivity Deff ranged from 6.40×10-8 m2/s to 4.55×10-6 m2/s.The nutrient retention and sensory scores of the diced apple dried by the coupled microwave convection were the best when the air temperature was 64.3 ℃.The results of this study provide a theoretical reference for the application of coupled microwave-convective drying for diced apples.
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