Optimization of drying conditions and component to reduce wall sticking during spray drying of infant formula milk

Abstract. Wall sticking, which greatly reduces productivity and lowers product quality, has been a big challenge facing spray drying. Structure of drying tower and atomizer, as well as drying conditions are the main influencing factors. This research explores the possibility to reduce wall sticking by optimizing drying conditions and component so as to obtain higher recovery rate of infant formula milk powder. Response surface experimental results indicated that inlet air temperature, feed concentration, feed speed, as well as interactive effect of inlet temperature and feed concentration had significant influences on recovery rate for determined milk ingredient. According to mixture experiments at optimized drying conditions, whey protein, fat and lactose contents, as well as interactive effect of fat and lactose contents had significant influences on recovery rate. Wall sticking which greatly reduces productivity and lowers product quality influenced recovery rate significantly. Positive effects were observed for components (whey protein, fat and lactose contents) on recovery rate, while negative effect for interactive terms of whey protein and fat and terms of fat and lactose. On the optimized drying condition for our experimental facilities of 136°C, 19.80% and 4.07 mL/min, respectively for temperature, feed concentration and feed speed, the maximum recovery rate was obtained at a whey protein, fat and lactose content of 18%, 31% and 51%, respectively. Wall sticking phenomena could be reduced by optimizing drying conditions and mildly adjusting components of infant formula milk.