Residence time distribution and kinetics of insolubility of skim milk powder during spray drying

Abstract

In spray drying, the particle residence time is the duration of atomized droplet spent inside the drying chamber. Residence time distribution (RTD) is a critical parameter in spray drying that plays a significant role in the properties of the dried powder and the efficiency of the drying process. This study determined the RTD of skim milk powder (SMP) at the drying tower during spray drying using the GEA NIRO mobile minor under various operating conditions. The method was validated using two different feedline systems (short and long) under two distinct operating conditions (hammering and non-hammering). The mean residence time without hammering and hammering conditions were 17 and 23–27 s, respectively. This study also assessed the insolubility formation of SMP at different drying conditions. The insolubility formation of SMP increased with the drying temperature and mean deposition time. The formation of insoluble material followed the first-order kinetics and was well described by the Arrhenius-type relationship. Quantitative wall deposition during drying was 63–75% of the feed dry matter. This study might help optimize the spray drying process, achieving consistent and high-quality spray-dried products.