A lab scale single droplet drying (SDD) kinetics device, based on acoustic levitation, was setup. This allowed drying of single droplets using dry air and/or infrared (IR) heating. It was used to investigate the effect of physicochemical properties of the liquid feed on particle formation, and IR wavelength on heating efficiency. To investigate the possibility to use microwave drying during powder production, a lab scale process was designed, allowing production of a powder with innovative functional properties.
Three draft publications and a patent were prepared and they will be submitted starting from March 2019. Two publications focus on: (i) morphology development in single drop drying for whey protein (WPI) solution and its colloidal aggregates; and (ii) IR laser heating of single droplets. The patent is about innovative protein based dried products. The third publication will follow the patent, reporting the innovative properties of the developed product and guidelines for its production.
Projects results were presented at European and international conferences and at industrial seminars. They will continue to be presented in the coming year. In addition, this project set science for processing new structure with innovative functions, which will be followed up by future research projects. Results were also well received by industry partners acquired during the project.
Following the main scientific results are presented.
- Morphology of WPI solutions and its colloidal aggregates
The control of particle morphology during the SD of food powders is one of the key factors affecting powder properties in food applications, in a dry and reconstituted state. Generic research in the field of drying of colloid suspension revealed the key mechanisms in play for systems whose behavior may be modeled with a few parameters describing colloidal interactions, Brownian motion, evaporation rate, as well as hydrodynamic stresses generated during drying. In this study, we validate models used to predict and control morphology of nanoparticles, for WPI powders, which are of main interest for pharma/food industries. WPI was used in its native and aggregated state. Single particle of WPI solutions were dried using the SDD device. Results showed that the morphology development and final morphology of the particles are significantly affected by colloidal size. Such phenomenon was successfully explained by calculating relevant parameters for describing mechanical properties of particle shell. In conclusion, we showed that it is possible to achieve diverse final morphologies of particles using same drying conditions and starting from the same type of colloids (WPI) but with different degree of aggregation. In addition, it is possible to predict final morphology of particle by estimating mechanical properties of the particle shell. This fundamental knowledge establishes the base for controlling particle formation and functionality of food/pharma dried products.
- Electromagnetic drying of single particles
The goal of this study was to improve thermal efficiency of the SD process by combining electromagnetic and convective heating. To understand potential of this novel methodology, electromagnetically assisted drying of single droplets was performed. Self-engineered electromagnetically assisted heating systems were tested for trials food feeds droplets, water and oil based. It allowed heating and drying single droplets at different power and wavelengths. Results showed that heating/drying of oil/water based droplet was instantaneous and fast cooling was possible since the surrounding air was not heated. Efficient heating/drying was achieved using larger wavelengths and higher power, thanks to the greater penetration depth.
In conclusion, single droplets were successfully dried using a IR heating system. By selecting the right wavelength drying efficiency was improved. Since no air flow was needed to heat the droplet, intermittent heating was performed as well as rapid cooling. Combination of electromagnetic energy and SD is a novel technology. This study set the base for the development of efficient drying techniques in the food/pharma/chemical industry.
