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

• Published in: Journal of food engineering 2018-03, Vol.221, p.11-19
• Main Authors: Gili, Renato D., Torrez Irigoyen, R. Martín, Penci, M. Cecilia, Giner, Sergio A., Ribotta, Pablo D.
• Format: Article
• Language: English
• Subjects: Effective diffusion coefficient; Effective heat transfer coefficient; Fluidization; Mathematical modelling; Wheat germ
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2017.09.029

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. •Fluidised bed drying of wheat germ particles at 90–150 °C was studied.•Two analytical solutions with constant diffusivity and constant volume were tested.•The solution for short dimensionless times was not suitable in this process.•The complete analytical solution, a series, provided excellent agreement with data.•Heat transfer coefficient and Arrhenius parameters were estimated solving inverse problems.