Particle morphology development of food materials during drying

Spray drying is a widely used process providing powders with long shelf lives which can easily be transported and readily reconstituted. During spray drying, droplets generated by atomization of the feed are converted into particles with a particular size, surface composition, and morphology depending on both the material properties and the process parameters. The morphology of primary particles greatly determines the characteristics of a powder formed from these particles or from agglomerates of primary particles. Therefore, tailoring the primary particle morphology is desired for producing powders with superior bulk properties. Morphology development may also be critical for the protection and controlled release of active ingredients or retention of volatile substances. Despite the widespread use of spray dryers, it is still a difficult task to adapt the primary particle morphology during spray drying towards desired applications as there is limited understanding of the key factors responsible for the morphology development. Lack of understanding and accordingly inefficient control of the morphology evolution of particles may result in material losses when the product fails to meet the required quality standards.

A more thorough understanding of morphology development is required to advance particle engineering during spray drying. In the present work, we improved our understanding of morphology development by relating the fundamental properties of the drying materials to the dynamics and skin properties of drying single food droplets. To do this, we aimed to predict the skin properties during drying and the final particle morphology, from the rheological properties of the constituents depending on concentration and temperature. The insights obtained in this work may offer a route towards multi-scale understanding and better control of spray drying processes.