Abstract
Particle morphology development during spray drying is critical to powder properties. The aim of this study was to investigate whether the dextrose equivalence (DE) of maltodextrins can be used as an indicator for the final particle morphology. Maltodextrins were characterized on glass transition temperature (Tg) and viscosity, where low DE-value maltodextrins exhibited higher Tg and viscosity than high DE maltodextrins (≥21). A new custom-built sessile single droplet dryer was used to analyse morphology development of minute maltodextrin droplets (R0~100μm) at 60°C and 90°C. Droplets with low DE showed early skin formation (2-5s) and developed smoothly shaped particles with large cavities. Rheology on low DE maltodextrin films at dry matter of 82% (w/w) suggested that drying droplets acquired elasticity after locking providing resistance against surface compression. After locking morphology development is probably halted as the glassy state is approached. On the contrary, rheology on high DE maltodextrin (≥21) films at dry matter of 93% (w/w) suggested that drying droplets with high DE developed viscous skins, which are susceptible to surface deformations, leading to wrinkling, folding or creasing particle morphologies. The results demonstrated that DE-value may be used as an indicator for particle morphology development when interpreted in view of the process conditions.
Highlights
Drying of fluids, containing for example polymers and colloids, has gained great interest during the last decade (Both, Nuzzo et al, 2018; Fu, Woo, & Chen, 2012; Giorgiutti-Dauphiné & Pauchard, 2018; Lintingre, Lequeux, Talini, & Tsapis, 2016; Meng, Doi, & Ouyang, 2014; Sadek et al, 2015)
Others found a linear correlation between the dextrose equivalence (DE)-value and glass transition temperature (Avaltroni, Bouquerand, & Normand, 2004; Levine & Slade, 1986; Roos & Karel, 1991), which is in line with the well-known Fox-Flory equation (Fox & Flory, 1950). In this specific study we investigate whether the DE of maltodextrins can be used as an indicator for the final powder particle morphology
Particle morphology development during spray drying is critical to the final powder properties
Summary
Drying of fluids, containing for example polymers and colloids, has gained great interest during the last decade (Both, Nuzzo et al, 2018; Fu, Woo, & Chen, 2012; Giorgiutti-Dauphiné & Pauchard, 2018; Lintingre, Lequeux, Talini, & Tsapis, 2016; Meng, Doi, & Ouyang, 2014; Sadek et al, 2015) Droplets of these fluids acquire different morphologies according to the material properties and conditions applied during formation. Pauchard and Allain (2003a) studied buckling instabilities of colloidal particle suspensions and polymer solutions using sessile single droplet drying They concluded that buckling requires a permeable, somewhat rigid skin which may still bend under the pressure of solvent evaporation. Vacuole formation during drying of whey protein droplets was well described by Bouman et al (2016) and Both, Karlina et al (2018) and requires a rigid skin that resists bending, but still allows permeation of the solvent
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