Effect of blanching on the dielectric properties and microwave vacuum drying behavior of Agaricus bisporus slices

• MWB increased ε″ while decreased ε′ of A. bisporus slices.
• MWB reduced the MVD duration of A. bisporus slices.
• MWB increased the hardness of microwave-vacuum dried and freeze-dried samples.
• MWB helps A. bisporus slices in formation of uniform honeycomb structure after MVD.

The aim of this study was to assess the effects of hot water blanching (HWB) and microwave blanching (MWB) on the dielectric properties and microstructure of Agaricus bisporus slices before and after microwave-vacuum drying (MVD). A. bisporus samples subjected to MWB had the lowest dielectric constant (ε') and the highest dielectric loss factor (ε''), whereas the samples subjected to HWB had a relatively lower ε'' at 25 °C and 2450 MHz. MVD was applied effectively to the initial stages of drying A. bisporus slices when the moisture content was higher than 2.27 in dry basis (d.b.). The MVD duration of MWB samples was approximately 17.5 min, which was reduced by 22% compared with that of HWB samples. The micro-structure of the MVD-treated MWB sample was more uniform than that of the HWB sample. These results suggest that MWB improves the MVD process when applied to A. bisporus before drying.