Spray drying droplets for a better quality end product

On July 5th, Eline Both defended her PhD-thesis on spray drying. Scroll down to read more about Eline and her promotion.

Spray drying is a widely applied manner of drying products in the food industry. Chances are that you have a few spay dried items in your pantry right now. Instant coffee, protein shakes, milk and egg powders are all examples of spray dried food products. These products are of superior quality to some other dried food products because of the mild way in which they were dried. Drying processes in the food and other industries are very energy intensive. This is why finding ways to make these processes more efficient while also focussing on a better quality end-product are a main focus of many research projects.

Identifying the factors that determine product quality

In her project PhD researcher Eline Both has used a single droplet drying approach to study the process of spray drying as a part of the ISPT drying & dewatering cluster. The project focussed on better understanding the drying process and identifying the factors that are important in determining the quality of the product. One of the key factors in determining product quality is the particle morphology, or shape, of the primary powder particle. Particle shape is closely linked to functional powder properties such as dissolution and flow ability properties. Better understanding of particle morphology will thus contribute to an improved powder quality. It will also help to improve the  efficiency of spray drying operations as better control of particle formation will reduce the risk of fouling in a spray drying tower, which leads to downtime and material loss.

Understanding morphological particle development

The main objective of this research was to create a mechanic understanding of particle morphology development in drying droplets specifically. One part of the research focussed on the skin formation of the particles and the other on whether the rheological, or flow, properties of components at high concentrations may explain the particle shape development during drying. The research concluded that especially composition and drying temperature influenced the final particle shape. Particles dried at low temperature or having a high whey protein content were more likely to form hollow particles, whereas particles dried at higher temperature or a high maltodextrin content (a food additive produced from starch by hydrolysis) had the tendency to become wrinkled. To find out all about the researcher’s findings related to the factors influencing morphological development read the full public summary here.

Applying knowledge gained in the lab in industrial processes

To conclude the research, and to help gain insights on a larger scale, the results from the single droplet drying research were compared to the morphological development of particles in a pilot scale spray dryer. This showed the importance of looking at drying from a product perspective and it emphasized the industrial relevance for this research as the morphologies observed in the pilot scale drying were similar to the observations seen in the single droplet drying experiments. This also underlined the relevance of single droplet drying methods for the purpose of observing morphology development during spray drying.

About Eline Both

Research: Powder Morphology Development during Spray Drying

Five years ago, Maarten Schutyser approached me if I would be interested in a PhD project on spray drying. This project was within the framework of the Institute for Sustainable Process Technology.

My research was about morphology development during spray drying. Many researchers already investigated the process of spray drying, but the mechanisms behind particle morphology development are still unknown. In my PhD I investigated the morphology development of single droplets and related these to the rheological properties of the ingredient formulations. Finally, I compared the single droplet drying results to spray drying on a pilot-scale.


I found that ingredient properties have major influence on particle morphology development and that rheological measurements are valuable to explain skin development, which is critical to morphology development. This was shown for whey protein, maltodextrin and mixtures thereof, and it could explain whether a particle would wrinkle or not, and what the size and number of vacuoles were. Finally, the morphologies observed in single droplet drying were similar to those from pilot-scale drying, and could be altered by changing the drying conditions.


I collaborated with industrial partners of the ISPT drying and dewatering cluster in my project. I learned a lot from working together with drying experts from industry and discussions during meetings with them contributed to better project results. In return, my work has contributed to increase our fundamental knowledge of spray drying and can thus help to steer spray drying processes towards higher energy efficiency and better product quality. Overall, I think our collaboration has been really fruitful!


This project is co-funded by TKI-E&I with the supplementary grant 'TKI- Toeslag' for Topconsortia for Knowledge and Innovation (TKI’s) of the Ministry of Economic Affairs and Climate Policy.