Work

Long-Term Survival of Cronobacter sakazakii, Salmonella enterica, Listeria monocytogenes, and Enterobacter spp. in Powdered Infant Formula Based on Relative Humidity

Year: 2025

Type: article

Abstract: • All bacteria survived for up to 360 d in powdered infant formula (PIF) at 25°C. • All bacteria persisted in PIF for ≥90 d without significant population reductions. • Minimal changes in PIF a w dramatically affected the survival of bacteria. Powdered infant formula (PIF) has previously been shown to support the survival of bacterial foodborne pathogens including Cronobacter sakazakii , Listeria monocytogenes , and Salmonella enterica at various storage temperatures. However, the effect of long-term storage on bacterial survival under different relative humidity (RH) conditions is not well understood. In this study, milk-based powdered infant formula (water activity (a w ) = 0.27) was inoculated individually with cocktails of Salmonella enterica , Enterobacter spp., Cronobacter sakazakii or Listeria monocytogenes and stored at 25°C under controlled relative humidity (RH) levels of 23, 33, 43, 53, or 75%. Bacterial populations and PIF a w were measured at intervals up to 360 days. The highest a w of 0.39 was recorded for PIF stored under 75% RH after 90 d or at 53% RH after 360 d, however these levels also resulted in significant bacterial population reductions of > 1 log CFU/g after 60-120 d and 60-180 d, respectively, with L. monocytogenes being the least desiccation-resistant of those tested. RH levels between 23-43% did not result in a significant change in a w over 360 d, however bacterial populations did decrease, but to a lesser extent, than for the higher RH levels. Population reductions for all bacteria were ≤ 3.50 log CFU/g after 360 d. All four bacteria examined in this study persisted in PIF for ≥ 90 d without a significant decrease in population regardless of RH storage conditions.

Source: Journal of Food Protection

DOI: 10.1016/j.jfp.2025.100670