Capturing the effect of initial concentrations on the drying kinetics of high solids milk using reaction engineering approach
2013
Chew, Jia Han | Fu, Nan | Woo, Meng Wai | Patel, Kamlesh | Selomulya, Cordelia | Chen, Xiao Dong
Many industries practice trial and error method to achieve optimum process conditions for desired powdered product quality in the event of fluctuations in the feed concentration, which happens more often than not and leads to wastage in product, time and energy. This paper presents the thermal-moisture drying histories for skim milk droplets from 37 to 43 wt%, in order to study the effects of initial solids variation on drying kinetics. The changes in droplet temperature, diameter and moisture content during drying were directly obtained using a glass filament single droplet drying technique. The experimental data were interpreted using the reaction engineering approach, an activation energy-based model where drying is dependent on vapour density gradient at the material-air interface. It was shown that the drying profile was sensitive to the initial solid content of droplet at this range of concentrations, since attempts to apply a single master activation energy curve to describe drying kinetics yielded less accurate predictions. The model's predictions were validated experimentally for both moisture content and temperature profiles during drying. The proposed approach enables drying histories of high solids milk to be modelled more accurately and could potentially assist in evaluating process design for high solids milk drying. ©INRA and Springer-Verlag France 2013.
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