Heterogeneous particle structure formation during post-crystallization of spray-dried powder--颗粒学报PARTICUOLOGY

Yazdanpanah, N., & Langrish, T. A. G. (2016). Heterogeneous particle structure formation during post-crystallization of spray-dried powder. Particuology, 27, 72-79. https://doi.org/10.1016/j.partic.2015.09.007

Heterogeneous particle structure formation during post-crystallization of spray-dried powder

Nima Yazdanpanah ^*, Tim A.G. Langrish

School of Chemical & Biomolecular Engineering, The University of Sydney, Sydney 2006, NSW, Australia

10.1016/j.partic.2015.09.007

Volume 27, August 2016, Pages 72-79

Received 15 May 2015, Revised 11 August 2015, Accepted 26 September 2015, Available online 23 December 2015, Version of Record 14 June 2016.

E-mail: nyaz3239@uni.sydney.edu.au

Highlights

• Changes in particle structure of milk powder during post-crystallization was investigated.

• The sorption and desorption of moisture into or from the surface layer played a significant role.

• A multi-component diffusion model was used to mimic experimental observations.

• Two types of particle structures were observed depending on post-crystallization conditions.

• Model predicted particle structures agreed qualitatively with experimental data.

Abstract

The formation of heterogeneous particle structure in skim milk powder has been investigated in a post-crystallization facility using experimental and a mathematical model. Various processing conditions were used to produce these heterogeneous structures. The experimental process parameters were used as initial and boundary conditions for the model. The modelled data agreed well with the experimental data. The experimental and modelling results show that the powder processed at high water activity (a_w = 0.7) with low initial moisture content ( = 0.01 kg/kg) developed a crystalline surface layer while the core of the particle remained amorphous. This structure is referred to as an egg-shell structure. The powder that was processed at low water activity (a_w = 0.1) with high initial moisture content ( = 0.2 kg/kg) developed a crystalline core while the surface of the particle remained amorphous. This structure is referred to as an egg-yolk structure. Understanding the dependency of particle microstructures on the processing conditions could be useful when developing procedures to control the drying equipment because the particle microstructure affects the physicochemical properties of the powder and potential applications and behaviour of the powder.

Graphical abstract

Keywords

Heterogeneous structure; Microstructure modification; Post-crystallization; Phase change; Complex domain matrix

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