Abstract:Aiming to improve the drying uniformity of corn ear and drying efficiency, reduce the quality loss, and optimize the design of drying and storage equipment for corn ear, a deep bed drying test equipment of corn ear was designed according to the drying technical requirements. The drying test equipment included hot air device, drying section, control system, temperature and humidity monitoring components. The corn ear drying characteristics and quality experiment were conducted at different wind speeds (0.5m/s and 1m/s), hot air temperature (room temperature, 50℃, 60℃ and 70℃) and material layer thickness (180mm, 360mm, 540mm and 720mm). The result showed that with the increasing of hot air temperature and wind speed, the drying rate was improved. When the wind speed was 0.5m/s, the drying time of the first material layer under the hot air temperature of 50℃, 60℃ and 70℃ was 28h, 20h and 14h, respectively. However, the moisture content (wet basis) of corn ear at room temperature drying only dropped to 20% after 192h. With the decrease of the hot air temperature, the drying time was significantly prolonged. Increasing hot air speed was beneficial forimproving the drying rate. The change of the drying rate of corn ears in the third and fourth material layersinfluenced by hot air speed was greater than that of the first or second layers. When the hot air temperature was 50℃, the drying time at the first material layer under the wind speed of 1m/s was 14.3% lower than the wind speed of 0.5m/s. With the increase of material layers, the drying rate under each drying condition was significantly reduced, and the drying time was prolonged. The material layer of corn ear at room temperature drying conditions was in a high-humidity environment for a long time. Drying corn ear in the stage of high water content by the natural ventilation method was easy to cause internal high humidity and high temperature. The moisture content of the corn kernel was decreased firstly during the drying process,and the moisture content of the corn cob was much higher than that of the corn kernel. Compared with the control group, the brightness value of the dried materials was decreased. Besides, the increasing of the hot air speed and temperature would decrease the brightness value of corn kernel. The electrical conductivity of corn kernels dried at room temperature was the lowest, which was 104μS/cm. With the increase of hot air temperature and wind speed, the electrical conductivity was increased, indicating that the internal structure of maize kernels was damaged greatly. The starch content and soluble sugar content of corn kernel were decreased after drying, among which the starch content was the lowest at 70℃, 0.5m/s and the soluble sugar content was the lowest at 60℃ and 70℃, 0.5m/s. On the basis of the drying characteristics and quality changes of corn ear, it was determined that the deep bed drying process of the corn ear was the method of hot air drying first and then drying at room temperature. The optimal hot air drying process parameters of corn ear was hot air temperature of 50℃ or 60℃, wind speed of 0.5m/s and air channel’s unilateral material layer thickness of 360mm.