Modelling of Convective Carrot Drying

Drying of carrots was investigated in a laboratory dryer with an electric heater and in a dryer with infrared irradiation. Before drying, samples were blanched in a 1 % aqueous solution of ascorbic acid and 0.5 % aqueous solution of sodium chloride. Based on the experimental data, the time dependency of moisture content, drying rate and diffusion coefficient were calculated and presented. These dependencies were approximated by using a two-parameter exponential model. It was established that such approximation could be used only for experimental results obtained in the infrared irradiation dryer, owing to the excellent set-up of the measuring device for monitoring changes in sample mass. Thus obtained measurement results are in high correlation with the calculations and indicate that, as expected, the applicability of the two-parameter model is conditioned by the availability of measurements of changes in the sample mass. The diffusion coefficient of moisture was determined for different experimental conditions, ranging between 1 x 10–7 and 6 x 10–6 m2 min–1 for blanched carrots in the 1 % aqueous solution of ascorbic acid, and between 1 x 10–8 and 1 x 10–5 m2 min–1 for carrots blanched in the 0.5 % aqueous solution of sodium chloride