Droplet drying behaviour of docosahexaenoic acid (DHA)-containing emulsion

•Drying of emulsions for the production of DHA-oil microcapsules.•Droplet drying behaviour of DHA emulsions is reported for the first time.•Different wall materials influence surface solid layer formation and shrinkage.•High solids create resistive barrier for water transfer at initial drying stage.

Docosahexaenoic acid (DHA), one of the poly-unsaturated fatty acids in omega-3 series, has attracted the attention of functional food industries due to its significant benefits to human health. DHA is often microencapsulated with modified-starch and whey protein concentrate (WPC) to reduce oxidation, to improve stability during storage, and to mask any unpleasant odour. Spray drying is a common method to manufacture encapsulated powders. To the best of our knowledge, there is yet any work reported on the drying behaviour of the DHA emulsions. In fact, there is no reported literature on droplet drying behaviour, especially drying kinetics, for fish/algae oil in water emulsion system. Here, the drying behaviour of different kinds of DHA-containing emulsion droplets with varying concentrations and wall-materials were investigated via a single droplet drying device utilising the glass-filament approach to yield representative kinetics data. The changes of droplet size, moisture content, and droplet/particle temperature during drying were recorded, with the Reaction Engineering Approach (REA) employed to correlate the data. The related mechanisms were also discussed. The model has been shown to provide an accurate description of drying behaviour of different systems. This model can be implemented in dryer-wide simulation software to investigate large scale operations, thus the current work has provided the essential basis for future large scale explorations.

Graphical abstractMorphological changes of an emulsion droplet containing DHA during drying at 70 °C as observed via the single droplet drying technique.Figure optionsDownload full-size imageDownload high-quality image (134 K)Download as PowerPoint slide