Smart particle production, characterization and powder forensics
thesisposted on 02.02.2017, 02:40 by Fang, Yuan
Powdered food ingredients are common yet important in our daily life. The most well-known method to produce these powdered products is via spray drying. Nowadays, it is possible to customize the spray dried products with desired nutrition/physiochemical properties according to the requirements and demands of the consumer market. Powders resulting from different processes (or different process conditions) vary significantly in composition and the functional behaviours. This renders traditional measurement techniques for characterising spray dried products to be insufficient and inadequate. Therefore, an effective and reproducible technique to benchmark different dairy powder functionality for both manufacturers and end-users usage is necessary and remains a challenge. This thesis reports the exploration of a possible ‘toolkit’ to characterize dairy powder functionality, benchmarking powder dissolution kinetics, and investigate the effects of spray drying conditions on powder functionality. A range of techniques applied in both industrial and laboratory for powder functionality characterization were reviewed, investigated and evaluated. A methodology to characterize the solubility of milk protein concentrates (MPC) using the technique Focused Beam Reflectance Measurement (FBRM) was established and presented. FBRM provides the ability to monitor in situ the changes in chord length with time over a wide range of suspension concentrations, which directly reflected the solubility of the investigated powder. A faster rate of the chord length reduction implied a better solubility as more particles break down and dissolve in solution. Using this protocol, the effect of water temperature for MPC powders was investigated and a characteristic dissolution profile for different MPC powders was subsequently established. Importantly, the measuring protocol of using FBRM to characterize dairy powder dissolution behaviour was established and validated. Using the established protocol, FBRM was used to monitor the dissolution process of MPC powder, with the data applied in the development of a kinetic dissolution model based on the Noyes-Whitney equation. The model was used to estimate two key benchmarking parameters, namely the dissolution rate constant k and the final particle size in suspension d∞, describing dynamic dissolution behaviors and final solubility respectively of a particular powder. The effects of dissolution temperature, storage duration and storage temperature on dissolution properties of an MPC powder were also investigated and a quantitative understanding of relationship between process and storage conditions with powder functionality were achieved from the k and d∞ profiles. Furthermore, the relationship between drying conditions and the functionalities and microstructure properties of the resulting products were established by investigating the effects of production drying air temperature on the functionality of MPC. To achieve this objective, mono-dispersed MPC particles were produced using a specially constructed dryer at selected drying air temperatures. Dissolution properties of the resulting MPC product were characterized using the established FBRM protocol, and the differences in microstructure examined from transmission electron microscopy images and micro XCT. A direct relationship between the drying air temperature and solubility was established whereby the solubility of MPC particle decreased with increasing drying air temperature. The degree of protein denaturation at different drying air temperatures was also established using gel electrophoresis. The knowledge could be used to establish a better understanding of the relationship between drying conditions and microstructures, and the corresponding influence on the functionality for different powder types. This PhD work established the basis measurement and protocol for characterising different powder types with varying functional and physical properties, the basis modelling fundamental approach to elucidate the mechanism of powder dissolution as well as demonstrated how the application of these protocols and approaches by establishing the relationships between powder production conditions to resultant product functional and physical properties. This work is the first step to establishing a standardised toolkit to establish a powder characteristic profile library to be use for production optimisation and rapid powder functionality analysis.