LIQUID DIFFUSION DURING DRYING OF SORGHUM GRAINS UNDER DIFFERENT CONDITIONS

ABSTRACT Drying is the most widely used process to ensure the quality and stability of plant products. Therefore, this study aimed to determine the effective water diffusivity and activation energy in grain sorghum during drying at different temperatures and initial moisture contents. Sorghum grains (cultivar DeKalb 640) were harvested with an initial moisture content of 0.49 kg water kg−1 dry matter. The effective diffusion coefficient was determined from different initial moisture contents of approximately 0.49, 0.40, 0.31, and 0.23 kg water kg−1 dry matter. Grains with different moisture contents were dried under four temperature conditions of 40, 60, 80, and 100 °C on perforated trays. The spherical geometry model was used for liquid diffusion. The experiment was conducted in a completely randomized design in a 4 × 4 factorial scheme (four moisture contents × four temperatures), with three replications. Data were subjected to analysis of variance and regression using the statistical software SISVAR®. Sorghum grain diffusivity increases at the same drying temperature as an increase of the initial moisture content of grains. The activation energy was higher for grains with higher initial moisture content, with values of 27.32, 26.75, 22.55, and 20.94 kJ mol−1, respectively.

摘要：干燥是保障植物产品品质与稳定性的最广泛应用工艺。本研究旨在探究不同温度与初始含水率条件下，粒用高粱干燥过程中的有效水分扩散系数与活化能。供试高粱品种为DeKalb 640，收获时初始含水率为0.49 kg水·kg⁻¹干物质。通过将初始含水率分别调整至约0.49、0.40、0.31与0.23 kg水·kg⁻¹干物质，测定其有效扩散系数。将不同含水率的高粱籽粒置于穿孔托盘上，分别在40、60、80与100 ℃四种温度条件下开展干燥试验。本研究采用球形几何模型进行液体扩散分析。试验采用完全随机设计的4×4因子方案（4种初始含水率×4种干燥温度），设置3次重复。采用统计软件SISVAR®进行方差分析与回归分析。结果显示，在相同干燥温度下，高粱籽粒的有效扩散系数随初始含水率升高而增大；初始含水率更高的籽粒活化能也更高，对应数值分别为27.32、26.75、22.55与20.94 kJ·mol⁻¹。