Assessing Hot Water Reconstitution Instructions and Labeling of Powdered Infant Formula to Ensure Cronobacter spp. Reduction

Cronobacter spp. contamination in powdered infant formula (PIF) can cause infections in high-risk infants. Public health guidelines for caregivers of high-risk infants advise reconstitution of PIF using water heated to at least 70 °C (158 °F) for microbial inactivation. This study evaluated changes to water temperature under different heating and cooling scenarios during formula preparation, aiming to identify which conditions best ensure a minimum treatment temperature of 158 °F (70 °C). Vessel type, lid usage, vessel removal from the heat source, and water volume were tested for their effects on heat retention. The "hot shot" method which uses a small volume of hot water followed by a larger volume of cooled water was also evaluated. In many scenarios, water temperatures fell below 158 °F (70 °C) during the steps prior to PIF reconstitution. The water temperature prior to transfer to the bottle, bottle material, and capacity, and volume of transferred water significantly impacted temperature (p < 0.001). The temperature of formula immediately following shaking was as high as 179.5 ± 1.6 °F (81.9 ± 0.9 °C) and as low as 138.0 ± 1.3 °F (58.9 ± 0.7 °C), depending on the preparation conditions. Bottle material and capacity, water volume, and initial water temperature significantly impacted the temperature of reconstituted PIF. Small volumes (2 fl. oz) of water in small glass bottles cooled the quickest. The hotshot method yielded temperatures well below 158 °F (70 °C). Measuring the temperature of hot water in the bottle and adding PIF when it cooled to 165 °F (73.8 °C) resulted in formula temperatures at or above 158 °F (70 °C) in almost all cases achieving a >5 log CFU/mL C. sakazakii reduction. However, 30 s of passive cooling was required to ensure pathogen lethality. PIF labels were reviewed, and lacked detailed information about how caregivers of high-risk infants should use hot water to reconstitute PIF. Our findings can help shape guidelines that improve PIF reconstitution practices.