Ultrasonically assisted atmospheric freeze-drying of button mushroom. Drying kinetics and product quality

The aim of this work was to evaluate the feasibility of using power ultrasound to improve the atmospheric freeze-drying of mushroom, as interesting alternative to vacuum freeze-drying, considering not only kinetic effects but also the final quality. For that purpose, mushroom slices (Agaricus bisporus) were dried (-10 degrees C and 2 m/s) with (24.6 and 12.3 kW/m(3); 21.9 kHz) and without ultrasound application. The application of ultrasound significantly influenced the drying kinetics, increasing the effective diffusivity up to 280% and shortening drying time up to 74%. As for the quality parameters (color, texture, rehydration, and cell damage), no remarkable influence of the ultrasound application was observed. Therefore, the application of power ultrasound during the atmospheric freeze-drying of mushroom might be considered as an interesting technology providing that it significantly increased the process kinetics without greatly affecting the quality of the final product.