The Risk Assessment That Changed How Formula Is Prepared

The study: FAO/WHO. (2006). Enterobacter sakazakii and Salmonella in powdered infant formula — Microbiological Risk Assessment Series No. 10.

Powdered infant formula isn’t sterile — and for the most vulnerable consumers (neonates, especially premature and immunocompromised), Cronobacter sakazakii (formerly Enterobacter sakazakii) contamination can cause meningitis and necrotizing enterocolitis with devastating mortality. The FAO/WHO risk assessment modeled the risk and evaluated interventions.

What the assessment found

The organism’s presence in PIF (low-level, heterogeneous), its extraordinary resistance to desiccation, and the risk factors: intrinsic contamination of the powder, and preparation practices (water temperature, holding time, feeding duration). The modeling showed that preparation with water at 70°C — killing the organism in the reconstituted formula — dramatically reduced risk.

The guidance that followed

WHO’s preparation guidelines (2007): water no cooler than 70°C, rapid cooling, short holding times, discard leftovers. Industry reformulation and process improvements. Hospital NICU protocols built around the guidance.

The risk assessment lesson

This is risk assessment at its most consequential: a vulnerable population, a severe outcome, and a clear intervention (hot water) validated by modeling. For manufacturers: the assessment also drove process improvements — the industry couldn’t rely on preparation alone. Environmental monitoring for Cronobacter, dry-plant hygiene, and ingredient control became standard. The 2006 assessment shows what risk assessment is for: not academic exercise, but identifying the intervention that saves babies’ lives, then implementing it globally.

The 70-degree compromise

The WHO guidance to prepare formula with water no cooler than 70°C is a risk assessment translated into a kitchen instruction — and like all such translations, it involves compromise. The temperature kills Cronobacter effectively, but it also degrades some nutrients, requires careful cooling before feeding (burn risk), and demands a discipline (thermometers, timing) that’s a lot to ask of exhausted parents at 3 AM. The guidance is scientifically sound and practically demanding, which is why implementation — not just publication — became the real challenge.

The hospital NICU setting shows what full implementation looks like: standardized preparation protocols, trained staff, audited compliance. The home setting shows the gap: surveys of preparation practices find widespread non-compliance with the temperature guidance, not from negligence but from the friction of real life. This is the eternal public health tension — the optimal instruction versus the followable instruction — and honest assessment acknowledges that some of the theoretical risk reduction is lost in practice.

The manufacturing side of the response is equally important and often underemphasized. The risk assessment didn’t just change preparation guidance; it drove process improvements — stricter environmental monitoring for Cronobacter, dry-plant hygiene standards, ingredient controls. The long-term solution isn’t hotter water in millions of kitchens; it’s cleaner powder from the factory. Both matter, but the manufacturing controls protect every infant including those whose caregivers never see the guidance. The 2006 assessment’s full legacy is the combination: better product plus better preparation, each compensating for the other’s limitations.

The risk assessment’s policy children

The FAO/WHO Cronobacter risk assessment’s policy children — the Codex code of hygienic practice for powdered formula, the microbiological criteria, the WHO preparation guidance — demonstrate the risk assessment-to-regulation pipeline working end to end. The assessment quantified the risk; the Codex translated it into the manufacturing standards; the WHO translated it into the preparation instructions. The complete chain, from the quantitative model to the nursery.

Source: FAO/WHO. (2006). Enterobacter sakazakii and Salmonella in powdered infant formula. Microbiological Risk Assessment Series No. 10.