Hot‐air drying of corn kernels: Drying kinetics and quality improvement

Abstract

AbstractBackground and ObjectivesDuring the hot‐air drying process of corn kernels, excessive stress can cause cracks to develop. For this reason, it's essential to identify the optimum parameters that can minimize stress during hot‐air drying.FindingsIn this study, a three‐dimensional fitness model was established based on the average geometric size of corn kernels. Additionally, a hot‐air drying model was constructed on the basis of heat and mass transfer, stress‐strain theory, and conservation law of heat and mass transfer. Simulated calculations of heat and mass transfer were performed to obtain the temperature and moisture gradient distribution. This distribution was then coupled with a stress model to reveal the variation of drying stress. Verification experiments were conducted on the drying model. The results indicated that the temperature and moisture gradient were symmetrically distributed about the geometric center of corn kernels. At symmetrical positions about the geometric center, their sizes were almost equal but their directions are opposite. The thermal stress and moisture gradient stress showed the fact of larger surface but smaller interior of corn kernels. Furthermore, they both increased rapidly in the initial stage and then slowly decreased. The maximum value of thermal stress was 4.57 kPa, and the maximum value of moisture gradient stress was 0.49 MPa.ConclusionsMass transfer plays a significant role in the hot‐air drying process, and cracks can develop as a result of excessive moisture gradient stress. To mitigate these issues, it's important to increase the air humidity in a controlled manner to significantly reduce the total stress. The maximum error in temperature between simulated and experimental results was 8.5%. This suggests that our drying model can be effectively utilized to explore temperature gradient, moisture gradient, and stress distribution of corn kernels.Significance and NoveltyThis study provides insights into the mechanism of stress generation that occurs during the hot‐air drying process of corn kernels. Our analysis indicates that properly increasing the air humidity can significantly reduce drying stress and consequently prevent the formation of cracks. This ultimately leads to improved product quality and economic value.