Heat, dry, survive: Up-stream parameters and matrix effects driving Salmonella enterica and Cronobacter sakazakii survival in whole milk and powdered infant formula during spray-drying

Milk powder and powdered infant formula (PIF) are long-shelf-life products, yet they're still occasionally linked to outbreaks. Infants, in particular, represent a vulnerable segment of the population, making contamination events especially concerning. This study investigates the impact of various spray-drying conditions on the survival rates of Salmonella enterica and Cronobacter sakazakii, previously subjected to sub-stress, in whole milk and PIF. Using a Taguchi design, we examined the influence of food matrix, initial dry matter concentration, sub-stress conditions, and bacterial strains on the survival of S. enterica and C. sakazakii. The results showed that PIF provides a highly protective environment and that desiccation sub-stress significantly increases bacterial survival. Understanding bacterial survival mechanisms during the spray-drying step, with regard to drying conditions, can help to improve the microbiological safety of powdered dairy products, thereby reducing health risks in vulnerable populations.