Capturing the effect of initial concentrations on the drying kinetics of high solids milk using reaction engineering approach

Abstract

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.

Exploring the drying behaviour and particle formation of high solids milk protein concentrate

“…However, a forced convection was necessary for any significant moisture removal, thus the activation energy has to increase if lower moisture content on dry basis was to be attained. Previous investigations found that SMP droplets of different initial solids, including those above 40.0 wt.% which were considered high concentration, exhibited similar drying behaviours at the later stage of convective dehydration and were able to be represented by an activation energy curve described by a common polynomial equation (Chew et al, 2013). This was similarly reflected in the MPC results (Fig.…”

“…The experimental data of SMP 20.0 wt.% and 40.0 wt.% were extracted from previous studies (Chew et al, 2013;Lin and Chen, 2002). The SMP powder contained 50.0 wt.% lactose, 33.5 wt.% protein, 0.7 wt.% fat, 12.0 wt.% ash and 3.8 wt.% moisture.…”

“…The REA is a semi-empirical model, which sees evaporation as an activation process and driven by vapour density difference between droplet surface and the drying medium. The main premise of the model is a material-specific master activation energy curve that provides accurate description to different thermal-moisture histories during drying of thin slabs or droplets under varied conditions, which is vital for dryer-wide modelling (Chen and Xie, 1997;Chew et al, 2013;Fu et al, 2012).…”

Three-Dimensional Numerical Investigation of a Mono-Disperse Droplet Spray Dryer: Validation Aspects and Multi-Physics Exploration

“…As presented in the previous sections, the three-dimensional spray-drying model has been examined using the experimental data on single-stream mono-disperse droplet drying [5] and single droplet drying [30][31][32]47]. Upon obtaining reasonable results in the range of inlet temperatures of greater than 130 C, we decided to undertake some extra-calculations.…”

Unraveling the droplet drying characteristics of crystallization‐prone mannitol – experiments and modeling

“…Previous experimental works suggested that the drying kinetics of a wide range of material have been well correlated with the REA. These materials include, but are not limited to, lactose, sucrose, maltodextrin, skim and whole milk, milk protein concentrate, cream, whey protein concentrate, docosahexaenoic acid emulsion, kiwifruit, and silica gel . Notably, these materials are generally characterized as skin‐forming or aggregate‐forming materials according to their particle‐forming behavior during drying .…”