Innovations in spray drying technology for liquid food processing: Design, mechanisms, and potential for application

Spray drying is a well-established approach to converting liquid food into powder. This review discusses four types of spray drying techniques currently being used for that purpose, namely: pulse combustion (PC) spray drying, electrostatic spray drying (ESD), nano spray drying (NSD), and extrusion porosification (EP). PC spray drying is still in the development phase in the food sector, having the disadvantage of lacking industrial technology for heat-sensitive foods like milk or whey protein concentrates. On the other hand, it is able to reduce or even eliminate the viscosity limitations of atomizers, in addition to being considered a potential energy-saving option compared to conventional spray drying. ESD and NSD show promise in drying bioactive or heat-sensitive compounds like enzymes, cells, and vitamins. A nano spray dryer contains a spray mesh technology and electrostatic collector, which results in variations in particle size and product yield compared to traditional spray drying. However, the current types of equipment are only available on a laboratory scale. Also, NSD could be unfavorable when considering the low concentrations of feed solutions (0.1–1% w/v). Finally, EP is claimed to provide better physical powder characteristics and permit the drying of highly concentrated liquids. It is hoped that these additional features and technologies will be further investigated in food systems to enhance process performance and improve powder properties.