New drying strategies that use low temperatures can have a significant impact on the improvement of food quality, in particular regarding the retention of flavor compounds, bioactives and other thermosensitive components. The vacuum spray dryer (VSD) is a spray dryer that operates with a low-pressure drying chamber, which consequently reduces the increases the thermodynamic driving force for water removal and allows drying at significantly reduced temperatures. In order to understand the process behavior and define operational strategies, a mathematical model that encompasses mass and energy balances was validated with experimental measurements of pressure and temperature during drying of large chained maltodextrin (dextrose equivalent = 10). Results from experiments carried out in a pilot VSD present a good fit with the proposed model and confirmed its underlying assumptions. In addition, comparative analyses were performed regarding physical aspects of particles produced by VSD and by conventional spray dryer (SD) in the same equipment, but without vacuum. Under the tested conditions, VSD particles presented a higher moisture content (8%) and smaller time of wettability than SD particles. The morphological changes were caused by the vacuum and can be interesting for technological applications.
Bibliographical noteFunding Information:
This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001.
- Drying modelling
- Energy balance
- Glass transition
- Spray drying