Examining of mass transfer factors and the vitamin loses during drying of the cornelian cherry with the infrared heath

In this work, during the drying proses of the cornelian cherries, effect of infrared output power on drying time, drying kinetics and mass transfer parameters are examined. In order to understand the mass transfer mechanisms, the modeling studies were carried out using two separate methods for the both cases in which the external resistance against the mass transfer is neglected and not neglected. Furthermore, the variation of some quality parameters such as Vitamin C loses, rehydration capacities and the color changes with infrared power output was investigated. All the experimental and theoretical calculations are carried out at 250, 300, 350, 400, 450, 500, 550, 600 W infrared powers. Under these conditions, final moisture contents of all the samples were successfully reduced to the value of 10 % (±1) and it was noted that drying times varied within the range of 275, 235, 185, 135, 105, 85, 67 and 50 minutes respectively. Drying rate increased with increasing infrared power. After a very short period of heating stage, it was recorded that a constant drying rate followed by falling rate period was observed. The range that constant rate occurred decreased with increasing power output. In the studied based on the assumption that the external resistance against mass transfer is neglected, in other words only the internal resistance was the dominant mechanism, it was found that the effective diffusivities increased with the infrared power output and that their values changed between 9.93x10-11 m2/s, 1.17x10-10 m2/s, 1.48x10-10 m2/s, 1.98x10-10 m2/s, 2.56x10-10 m2/s, 3.21x10-10 m2/s, 4.01x10-10 m2/s, 5.39x10-10 m2/srespectively. Experimental results were in very good comparison with the Page model defined by amongst the most widely used 10 different models in literature with the lowest χ2, RMSE and the highest R2 parameters. On the other hand, for the second situation in which the external resistance against the mass transfer is also effective, Biot number-drying coefficient (Bi-S) model was used. Because the Biot number is the most important non- dimensional parameter expressing resistance against the mass transfer and also the existence of constant drying rate period was taken into consideration , within the range of 250-400 W, only the external resistance is dominant, however, for the range of 450-600 W infrared power outputs, both external and internal resistances are available. In the range of the experimental studies were carried out , it was recorded that the Biot numbers had the values of 0.073, 0.078, 0.084, 0.093, 0.102, 0.114, 0.0119, 0.0130, and Deff had the values of 9.59x10-10 m2/s, 1.37x10-9 m2/s, 1.64 x10-9 m2/s, 2.13 x10-9 m2/s, 2.68 x10-9 m2/s, 2.05 x10-9 m2/s, 3.57 x10-9 m2/s and 4.76 x10-9 m2/s respectively. With the increase in the infrared heat, some decrease in the color parameters of dried Cornelian Cherrys samples was observed. It was found that rehydration capacities decreased with the increase of infrared power output. Finally, it was determined that Vitamin C values of dried Cornelian Cherry samples were lower compared to those of the fresh samples, and infrared power output played a very important role on the loses of Vitamin C values.