Drying of a Low Porosity Product (Carrot) as Affected by Power Ultrasound

The main aim of this work was to assess the influence of power ultrasound on mass transfer process during convective drying of a low porosity product submitted to different acoustic energy levels. Drying kinetics of carrot cubes (side 8.5 mm) were carried out at 40 °C and 1 m/s applying different electric power levels to the ultrasonic transducer: 0, 10, 20, 30, 40, 50, 60, 70, 80 and 90 W. Drying kinetics were modelled considering the diffusion theory. From the results, a significant (p<0.05) influence of power ultrasound application on drying kinetics of carrot cubes was found. Drying rate increased as the electric power applied got higher. The influence was only observed above an acoustic energy threshold, which corresponded to an electric power applied to the transducer of 20-30 W. From this threshold, a linear relationship was found between the average effective moisture diffusivity or the mass transfer coefficient and the electric power applied to the transducer.