Personal Injury Law

Mind the baby: Bacterial risks when preparing powdered infant formula

By Doug Powell

Long-time FSnet/bites fan, first-time contributor, Steve Forsythe of Nottingham Trent University sends along this bit he prepared for the U.K. Food Standards Agency.

Who knew preparing infant formula could be so complicated? I've been doing it for months and didn't give it much thought. This food safety stuff is tough, it sure ain't simple, and cross-contamination once again features prominently.

From the executive summary:

Powdered infant formula (PIF) is a generic term used to cover a range of breast milk fortifiers and substitutes. These are not manufactured as sterile products, but are intended to conform to appropriate microbiological specifications. For PIF in international trade these were recently revised by Codex Alimentarius Commission (CAC 2008). Previous FAO/WHO 2004 and 2006 expert meetings on the microbiological risk assessment of powdered infant formulas have recommended the reconstitution of PIF with water no less than 70°C, and used within 2 hours. The use of high reconstitution temperature is considered to reduce the viable count of Cronobacter spp. and Salmonella serovars and a short storage period would limit the growth of any survivors, and therefore this practice would reduce the risk of neonatal infection through the ingestion of contaminated infant formula. However it is apparent that various preparation practices are used by caregivers. This report considers the risk associated with bacterial survival and subsequent multiplication following reconstitution at <70°C, for Cronobacter spp., Salmonella, other Enterobacteriaceae and Acinetobacter spp. Therefore it considers organisms previously designated of concern due to clear evidence of causality between infant infection and infant formula contamination, and those for which the causality was plausible, but not yet demonstrated; FAO/WHO (2004 & 2006) Category A and B organisms.

Summary points:

1. It is not feasible for caregivers to easily judge the temperature of reconstitution water in order to meet the >70°C guideline. Reconstitution using water which had been boiled and left for 30 minutes resulted in temperatures ranging from 46 to 74°C depending on the volume of water boiled. This results in different degrees of lethality to bacteria, but boiling 1000ml of water gave temperatures on average >70°C after 30 minutes.

2. In general, bacteria had similar growth rates in whey-based (or first milks) infant formulas compared with casein-based (or second milks) infant formula. However, in whey-based infant formulas they were more heat tolerant and had shorter lag-periods. These resulted in differences in predicted outcomes following reconstitution at various temperatures using the JEMRA E. sakazakii risk model; point 5 below.

3. There was variation in thermotolerance between Cronobacter strains, with no single Cronobacter species more thermotolerant than the others. All Cronobacter were less thermotolerant than the well described, highly thermotolerant strains of Salmonella enterica serovar Senftenberg. Of the remaining organisms, the most thermotolerant organism was a strain of Enterobacter hormaechiae, which was nearly twice as thermotolerant as Salm. Senftenberg at 55oC.

4. The upper growth temperature varied within the Enterobacteriaceae, with Cr. sakazakii, Cr. malonaticus, Cr. dublinensis, Ent. cloacae, and Esch. coli being able to grow at 44°C.

5. Bacterial growth and death rates in whey- and casein-based infant formulas for Cronobacter spp., Salmonella serovars, other Enterobacteriaceae, and Acinetobacter spp. (Category A and B organisms; FAO/WHO 2004 & 2006) were used with the JEMRA E. sakazakii risk model for 7 scenarios with reconstitution temperatures between 10 and 70°C. For all scenarios, reconstitution at 70°C predicted decreases in bacterial numbers ranging from 1 log for Salm. Senftenberg and Salm. Enteritidis, to >104 log decrease for Cr. sakazakii and was dependent on the formula base. The model also predicted overall decreases in bacterial numbers for all scenarios when the reconstitution temperature was 60°C, although this was less than a 0.5 log decrease for some strains. In contrast, at 50°C some strains had predicted increases depending upon the scenario and the formula base. For all strains growth was predicted for 2 scenarios of mixing in a 1 or 25 L container, 1 h preparation time at room temperature (20°C), refrigeration (4°C) for 6 h, rewarm to 37°C, and feed within 30 min (37°C).

Full post as published by BarfBlog on January 14, 2010 (boomark / email).