BACTERIOLOGICAL QUALITY OF INFANT MILK FORMULAS EXAMINED UNDER A VARIETY OF PREPARATION AND STORAGE-CONDITIONS

One hundred infant milk formulae (IMFs), representative of the 10 lead ing brands available in the UK, were subjected to a variety of prepara tion and storage conditions. Each IMF was the subject of triplicate tr ials in which duplicate samples were analyzed. All IMFs analyzed immed iately after reconstitution were of satisfactory bacteriological quali ty, exhibiting a total aerobic count of <10(4) CFU g(-1) (mean 2.3 x 1 0(2) CFU g(-1)) and a Bacillus cereus count of <10(3) CFU g(-1) of pow der (mean 1.3 x 10(2) CFU g(-1) for formulae containing this bacterium ). Seventeen percent of all dried IMF examined contained B. cereus; su bsequent reconstitution and storage over a 24-h period at greater than or equal to 30 degrees C resulted in this organism being detected in a further 46% (63 of 100), so that the majority of these foods exceede d the International Dietetics Association of the European Community (I DAEC) proposed reconstitution safety limit of 10(3) CFU g(-1). Variati ons in preparation conditions did not significantly influence the numb ers of Bacillus CFU present (P < 0.05). The bacteriological quality of an IMF depended on the type and number of organisms initially present and on product temperature and duration of product storage. Microbial numbers in IMFs were influenced by storage temperatures of greater th an or equal to 20 degrees C for 14 h, while incubation at less than or equal to 10 degrees C for 24 h had no effect (P < 0.05). Although the microflora of dried IMFs predominantly consisted of B. licheniformis (46%) and B. subtilis (30%), subsequent reconstitution and incubation resulted in the shift to B. cereus I (31%) and II (38%) as dominant or ganisms. The latter often grew to the exclusion of the former two Baci llus spp. Diarrheagenic enterotoxin was detected in 4% of IMFs analyze d after 14 h of storage at greater than or equal to 25 degrees C.