Investigation of the effective factors in hot air drying process on quality characteristics of lentil

In order to prevent physical damage, it’s recommended to harvest lentils at a humidity of 20%, and then reduce it to less than 12%. Remaining the plant on the field as the conventional drying method reduces the quality and quantity of lentil product. The main purpose of this study is investigation of lentil quality characteristics in different drying conditions in order to determine an optimal condition and design a specified dryer system which can dry lentil with sufficient quality characteristics. In this study, lentil grains were dried using a hot air dryer at four temperature levels of 50, 60, 70 and 80°C and three air flow velocities levels of 1, 1.5 and 2m.s-1 until the grain moisture reached to 12%. Then their qualitative characteristics were examined. Increasing the temperature and air velocity accelerated the samples drying time consumption. With increasing temperature, air velocity had less effect on the drying time of the samples. Also, with increasing both temperature and velocity factors, the required compression force increased. On other hand, with increasing temperature, the brightness of the samples (L) decreased and the color of the samples changed from green (-a) to red (+a) and changes in color parameter b showed that the intensity of yellow color in samples have been reduced. Increasing the temperature reduced the amount of protein and carbohydrates in the dried samples, in contrast, by increasing air velocity they were better preserved. Temperature had a greater effect on the protein and carbohydrate content of the samples than the air velocity. Also, the studied factors did not have a significant effect on the amount of minerals in the samples. Based on the results obtained in this study, it’s recommended to apply the drying process at lower temperatures (50 and 60 ° C) and maximum air flow velocity (2m.s-1).