中文摘要：

为了解莲子干燥过程中水分传递过程,监控、预测水分变化,该文通过开展莲子薄层热风干燥试验,考察了莲子在不同干燥温度（50、60、70、80、90℃）下干燥特性,建立了莲子热风干燥试验模型;利用低场核磁共振技术（nuclear magnetic resonance,NMR）,弛豫时间（transverse relaxation time,T2）和成像（nuclear magnetic resonance imaging,MRI）,考察了干燥过程中莲子内部水分分布状态与变化规律。结果表明,莲子干燥一直处于降速干燥段;干燥温度显著影响干燥过程（P〈0.05）,干燥温度升高,干燥时间缩短;通过比较4种数学模型,发现莲子干燥过程采用Midilli模型（决定系数R2〉0.998）进行准确模拟（相对误差E〈10%）;有效扩散系数在6.056 7×10^（-10）～1.660 3×10^（-9） m2/s之间,并随着干燥温度的升高而增大;活化能为24.268 5 k J/mol。核磁共振试验表明,半结合水是莲子的特征水分,占新鲜莲子总水分的85.59%,其脱除过程呈现指数特征（R2〉0.91）;干燥过程中,不同状态的水分流动性变差。莲子内部存在水分梯度,表层最先失去水分,莲芯水分最后脱除;干燥终止时,剩余水分主要存在于莲芯部位。MRI为确定莲子干燥终点提供了直观的参考依据。研究结果可为控制莲子热风干燥过程、优化干燥工艺参数提供理论依据。

英文摘要：

Lotus seeds are the seeds of plants in the genus Nelumbo, particularly the species Nelumbo nucifera in Asia and Africa. Lotus seeds are of great importance to East Asian cuisine and used extensively in traditional Chinese medicine and Chinese desserts. Drying process is one of the most important processes for lotus seeds, which can suppress activities of microorganisms, enzymes or ferments and maintain its nutrition content. Moisture transfer in lotus seeds during the drying is a complex process, and the safe moisture content is fundamentally important for industrial processes, because quality and energy consumption are related to moisture content. A better understanding of the mechanism of moisture transfer should help improve the product quality and efficiency of drying process. Thin-layer hot air drying characteristics of lotus seeds were investigated in the temperature range of 50-90 ℃ at a constant air velocity, and water mobility and distribution in lotus seed samples were estimated based on the nuclear magnetic resonance （NMR） methods （relaxation time and imaging） in this study. The results indicated that the drying process involved a deceleration phase, and had no constant-rate phase. The strong influences of drying temperature on drying rate and drying curve were evident. Four empirical drying models, i.e. Lewis, Herderson-Pabis, Page and Midilli model, given in literature for describing time dependence of moisture ratio change, were used to fit experimental data, and their coefficient of regression （R2） and root mean square errors （RMSE） were predicted and compared by non-linear regression analysis using the Matlab R2012b software. Relative percent error （E%） was used to determine the goodness of the moisture prediction during the drying. It was found that the Midilli model could predict drying curves compared with experimental data point for the drying of lotus seeds in temperature range of 50-90 ℃ （R2〉0.998, E〈10%）. The effective diffusivity was obtained using the Fick?