Behavior of Listeria monocytogenes in reconstituted infant cereals

Listeria monocytogenes may contaminate and grow in reconstituted infant cereals refrigerated or temperature abused before consumption. To assess this risk, a 5-strain composite of the pathogen was inoculated in rice, oatmeal, and wheat-rice-oatmeal infant cereals, hydrated (1/6, w/v) with apple juice, pasteurized milk (2% fat) or water, and stored at 4, 15, or 25C for 0, 8 and 24 h to simulate potential advance home preparation and abuse. L. monocytogenes survived with minimal (<0.6 log cfu per mL) or no growth in all cereal preparations at 4C, but it increased in cereals hydrated with water or milk by 2.4-3.3 and 5.3-6.4 log cfu per mL in 24 h at 15 and 25C, respectively. Reconstitution of cereals with water or milk supported growth (P < 0.05) even at 8 h of abuse. In cereals hydrated with apple juice and stored at 15 or 25C, populations of L. monocytogenes were maintained below 3.0 log cfu per mL at 24 h. These results indicate that refrigeration and/or reconstitution with an acid fruit juice may inhibit growth of L. monocytogenes in infant cereal meal preparations. However, in order to ensure prevention of growth, such meals should preferably be consumed soon after preparation or held at 4C for less than 8 h.