Atomisation technologies used in spray drying in the dairy industry: A review

Atomisation is an integral element of the spray-drying process, whereby a bulk liquid feed is converted to discrete droplets, greatly increasing the surface area of the feed liquid and thereby increasing considerably the achievable rates of evaporation of water. These droplets, through evaporation of water in the main dryer chamber, become individual powder particles during the spray-drying process. This review provides a comprehensive examination of the most recent developments in atomisation technology for spray-drying, with a particular focus upon dairy applications (e.g., skim and whole milk powders, casein- and whey-based powders, and fat-filled milk powders). As well as a review of principles of different technologies for atomisation, such as rotary atomisers, pressure nozzle atomisers, pneumatic atomisers, ultrasonic atomisers and electrospray atomisers, the industrial applicability and challenges in use of each approach to atomisation are presented. Approaches for monitoring the atomisation process and other factors that influence atomisation, such as feed composition and key process parameters, are considered to provide a holistic analysis of the atomisation process.