The main aim of this work was to evaluate the application of power ultrasound on the drying of salted cod at low temperature. For that purpose, drying experiments of salted cod slabs (length 50 x width 30 x thickness 5 mm) were conducted in a convective dryer with air recirculation, temperature and air velocity control, and an ultrasonically activated drying chamber. Air-drying (AIR) and ultrasonically assisted air-drying (AIR+US, 20.5 kW.m-3) experiments were carried out at -10, 0, 10 and 20°C at constant air velocity (2±1ºC m.s-1) and relative humidity (9±4%). A diffusion model was used in order to quantify the influence of ultrasound in drying kinetics.
Drying rate increased as air temperature was higher. At all temperatures tested, ultrasound application increased the drying rate, achieving drying time reductions between 35 and 50% by ultrasound application. The diffusion model considered described adequately the drying kinetics. The application of high power ultrasound increased significantly (p<0.05) the effective moisture diffusivity for all temperatures tested, the improvement ranged from 110% for the highest temperature tested, 20°C, to 42% for 10°C. The influence of air temperature on effective moisture diffusivity followed an Arrhenius type relationship for both AIR and AIR+US experiments.
Acknowledgements
The authors acknowledge the financial support of the Ministerio de Economia y Competitividad (MINECO) and the FEDER from the project DPI2012-37466-CO3-03.
