High outlet temperatures reduced the water content for Lactobacillus death during spray drying process

Spray drying often compromises lactic acid bacteria (LAB) viability due to thermal and dehydration stress. This study investigated how inlet and outlet spray drying temperatures affect Lactobacillus dehydration responses by analyzing air temperature and water content within the drying tower. We found that the outlet temperature significantly impacts bacterial viability more than the inlet temperature. For Lactobacillus bulgaricus sp1.1, dehydration inactivation occurred at an outlet temperature of 60 °C, with cell death observed around 32% water content. Conversely, at 120 °C/70 °C, combined stress caused severe membrane damage, reducing survival and prolonging acid production’s lag phase. The faster drying at 120 °C/70 °C also lowered the critical water content threshold to 25.6%. These findings illuminate the relationship between the critical moisture content of the death of LAB and the outlet temperature in the spray drying process and outlet temperature during spray drying, offering crucial guidance for optimizing LAB spray drying processes.