The effects of fermentation and or vacuum flask storage on the presence ofcoliforms in complementary foods prepared for Ghanaian children

Microbial contamination of complementary foods is a major cause of childhoo d diarrhoea. In a community-based study in Ghana, we evaluated whether ferm entation of maize porridge or storage of porridge in vacuum flasks reduces coliform contamination. The complementary food examined, Weanimix, consiste d of, on a dry weight basis, toasted maize (75%), peanuts (10%), and soybea ns (15%) milled into flour. The fermented food was Weanimix made with drum- dried, previously fermented maize. Fifty women with infants 6-18 months of age participated. A repeated measures cross-over design was used. Each moth er participated in all four treatments (1 week per treatment, in random ord er): (a) non-fermented Weanimix (W), (b) fermented Weanimix (F), (c) non-fe rmented Weanimix stored in a vacuum flask (WV), and (d) fermented Weanimix stored in a vacuum flask (FV). Each week, mothers were supplied with the ap propriate food, and asked to prepare a porridge each morning by boiling the dry mix in water. Samples were collected in the evenings and immediately p lated onto 3 M Petrifilm. Contamination was defined as greater than or equa l to 100 colony-forming units of coliforms per ml. Contamination rates (95% confidence intervals) were W = 48% (38-58%), F = 25% (17-34%), WV = 42% (3 2-52%), and FV = 13% (6-20%). All pairwise comparisons were significant (P < 0.05) except for W vs WV Within the WV treatment, contamination rates wer e 85% when the sample temperature fell below 50 degrees C (N = 41) vs 12% w hen it remained >50 degrees C (N = 59) (P < 0.001). These results indicate that contamination is reduced by fermentation, and further reduced by vacuu m flask storage of fermented foods. For non-fermented foods, vacuum flask s torage was protective only when the temperature was maintained at >50 degre es C; at less than or equal to 50 degrees C vacuum flask storage increased the risk of contamination.