Experimental study of fig drying using supercritical fluid of carbon dioxide

Drying foods, such as freezing methods and hot air, are not ideal and reduces the nutritional value and is also expensive and is used only for high value food. In this research, drying with supercritical fluid of carbon dioxide was investigated to remove moisture from the figs. In the drying process with supercritical fluid, the structure of food products is maintained during drying. The design of the experiment was carried out in a factorial arrangement using Design Expert software and analysis variance table to determine the effect of three pressure parameters, temperature, and time to measure the removal rate of moisture. The calculated factorial model was meaningful and able to select the best drying parameters. In optimum conditions, the highest yield (78.109%) with the desirability of 0.992 at 20 MPa, 60 °C and 120 minutes duration. The results showed that the drying of figs during the whole drying period is carried out at the downstream stage, which indicates that the drying of these materials, the internal moisture control, controls the rate of drying and mass transfer. In this study, by solving the second Fick's law and in the range of pressure and temperature tested, with the assumption of the spherical of the fig using the Crank equation, the amount of moisture diffusion coefficient between 4.51× 10-10 and 0.18 × 10 -10 m2/s were obtained. The fig's drying rate was also calculated. Increasing temperature and pressure caused to increase the drying rate.