Wheat germ thermal treatment in fluidised bed. Experimental study and mathematical modelling of the heat and mass transfer

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 (7.87-16.55 W/m2 °C). The effective diffusion coefficient for water was determined to vary from 3.22 × 10 −11 to 2.38 × 10 −10 m2/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.