Authors

Abstract

This study addresses the starch phase transitions induced by coupled temperature and moisture variations during paddy rice drying and the associated deterioration in grain quality. A mathematical model for intermittent drying was developed by integrating the glass transition mechanism with a three-dimensional realistic grain geometry. The model was validated using continuous drying (CD) and two-stage intermittent drying (2SID) experiments. The results showed excellent agreement between simulations and experimental data, with correlation coefficients exceeding 0.95. Model analysis revealed that during 2SID at 45 °C, the glassy region rapidly formed from the grain surface inward, accounting for approximately 19.6% of the total grain volume at the end of the first drying stage. After a 20-min tempering period, the internal moisture gradient was effectively reduced, and the glassy region expanded only slightly by about 2.1%. Following the second drying stage, the glassy region increased to approximately 47.9%, while the central layer of the grain remained in the rubbery state throughout the process. Compared with CD, 2SID not only reduced the total drying time by approximately 9.09% but, more importantly, significantly regulated the internal moisture distribution through the tempering stage, thereby helping to mitigate fissure formation and improve head rice yield. The proposed model provides a reliable theoretical framework and predictive tool for optimizing intermittent drying parameters and simultaneously enhancing drying efficiency and paddy rice processing quality.

Abstract in Chinese

本研究针对稻谷干燥过程中因温度与水分变化导致的淀粉相态转变及其引发的品质劣化问题，提出了一种融合玻璃化转变机制与三维真实籽粒几何的间歇干燥数学模型。模型通过连续干燥（CD）和两段间歇干燥（2SID）实验进行验证，结果表明模拟数据与试验结果高度吻合，相关系数均超过0.95。模型分析显示，在45°C的2SID过程中，玻璃化区域首先从表层快速形成，第一干燥阶段结束时约占籽粒体积的19.6%；经20分钟缓苏，水分梯度有效降低，玻璃区仅小幅扩展约2.1%；第二干燥阶段后，玻璃区总面积增至约47.9%，而中心层始终维持在橡胶态。与CD相比，2SID不仅将总干燥时间缩短约9.09%，更重要的是通过缓苏阶段显著调控了内部水分分布，从而有助于减少裂纹产生、提升整精米率。该模型为优化间歇干燥工艺参数、协同提升干燥效率与稻谷加工品质提供了可靠的理论工具与预测手段。