Trends of spray drying: A critical review on drying of fruit and vegetable juices

Spray drying is extensively used to preserve fruit and vegetable juices in powder form. The major concern is to obtain high quality fruit and vegetable powders, which requires optimization of spray drying conditions. High drying temperature damages sensitive bioactive compounds, carrier agent protects such compounds and other factors involved in spray drying affect physicochemical and microstructural attributes of the product. This review summarizes current trends of spray drying of fruit and vegetable juices, covering principles of spray drying, physicochemical and microstructural effects of spray drying conditions, optimization of spray drying conditions and new developments in spray drying. Several new techniques have been introduced into spray drying, helping to overcome its limitations. These techniques are posted to set new standards for the production of high quality fruit and vegetable powders in industrial application. The most significant factors in spray drying are inlet temperature and carrier agent. Successful spray drying enhances physical properties of powdered products, while preserving bioactive compounds with the help of carrier agents or their combinations. Response surface methodology is the most suitable tool for optimization of spray drying conditions. The application of ultrasound technique during atomization, vacuum drying chamber with controlled atmosphere, and supply of dehumidified air to drying chamber of basic spray dryer have distinctly improved the potential of the technology over conventional spray drying. These advances will contribute to further research improvement of drying of fruit and vegetable juices by conventional approaches as well as modified spray drying techniques.