Wheat germ is an abundant by-product of the milling industry, it has excellent nutritional qualities and high tocopherols content. The aim of this work was to study the kinetics of wheat germ drying in fluidised thin-layers by applying analytical solutions of the diffusion equation. Also, was determined the effective heat transfer coefficient by solving the macroscopic energy balance to contribute with the design and optimization of a thermal treatment for this product. Four air temperatures were studied in this work, 90-150°C. The heat transfer coefficients were estimated using experimental drying rates (7.87 to 16.55 W/m 2°C). The effective diffusion coefficient for water was determined to vary from 3.22 x 10-11 to 2.38 x 10-10 m 2 /s. The analytical solution for short times was not suitable for this high temperature process. Values of diffusion coefficient and activation energy (39.27 kJ/mol) were within the ranges expected for food drying at elevates temperatures.

Wheat germ is the embryo of de wheat seed, it contains a high tocopherol and protein content, and high quality proteins and fatty acids. Also, wheat germ has a considerable enzymatic activity that limits its shelf life. The aims of the study were to physically and sorptionally characterize wheat germ particles, select the more convenient model to describe the relationship between moisture content and water activity of wheat germ and to determine their design parameters of thermal fluidization process with air. The principal axes of the particle were measured by image analysis, and their dimensions and geometric parameters were calculated. Four isotherm models were fitted to experimental data. GAB model was the more accurate to explain the experimental data. The fixed bed density and the void fraction were measured. The fluid-dynamic studies permitted to determine laminar (277.46 ± 17.48) and turbulent (7.79 ± 0.69) coefficients of the Ergun equation and the minimum fluidization velocity (0.35 ± 0.02 m/s).

No abstract