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

Abstract

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.

Modelling Condensation and Simulation for Wheat Germ Drying in Fluidized Bed Dryer

“…The local sensitivity analysis approach was used to verify the model parameter. The criterion of the model verification was calculated by using the minimum of the absolute average deviation (AAD) [31]. The equation is defined as…”

“…An empirical type provides a direct relationship between average MC and time, but it neglects the physical correlation between the drying processes and their parameters [26]. Gili et al [31] successfully developed an analytical series solution for the microscopic diffusion equations and applied a theoretical thin-layer model coupling with a macro-heat transfer model to predict the MC of WG during drying in the FBD. They also observed that the moisture loss occurred in the falling drying rate period for WG drying in the FBD.…”

Drying Applications during Value-Added Sustainable Processing for Selected Mass-Produced Food Coproducts

“…Wheat germ is another mass-produced by product from wheat milling processing and containing many nutrients, such as carbohydrate, protein, fat, vitamins and minerals [39,80]. However, fresh wheat germ is not able to bear a long-term storage due to unsaturated fats and endogenous enzyme with high moisture content causing rancidity, which is produced by oxidation reaction [81].…”

“…Different drying processes are used to overcome this problem and the numerical method was also applied. Gili et al studied the dehydration of wheat germ using a fluidized bed dryer with both mathematical modeling and experiment measurements [80]. In their experiment, the fluidized bed dryer was employed at different temperatures (90,110,130 and 150 • C) at constant air velocity (0.5 m/s) [80].…”

“…Gili et al studied the dehydration of wheat germ using a fluidized bed dryer with both mathematical modeling and experiment measurements [80]. In their experiment, the fluidized bed dryer was employed at different temperatures (90,110,130 and 150 • C) at constant air velocity (0.5 m/s) [80]. At 150 • C, the Becker model was not correctly described by the whole drying process [15].…”