Effect of accelerated natural lactic fermentation of infant food ingredients on some pathogenic microorganisms.

Accelerated natural lactic fermentation in mixtures of water and ground sorghum, millet and pigeon pea was obtained by gradual selection of lactic acid bacteria, through inoculum recycling. Weaning food prepared from ingredients fermented this way, contained approx. 0.7% lactic and 0.05% acetic acids and had a pH of about 3.8. In porridges, a pH of less than or equal to 4.0 was required to cause death of Salmonella typhimurium and Staphylococcus aureus. Several intestinal pathogenic bacteria were inoculated into sour porridge. The most resistant Salmonella sp. died at a rate of 1.2 log cycle/h; the most resistant Shigella sp. at 0.9 log cycle/h; and the most resistant Escherichia coli strain at 0.6 log cycle/h. A yeast, Candida albicans, could grow well in the sour product, whereas a bacteriophage (MS-2) was inactivated at a rate of 0.1 log cycle/h. In the acid-sensitive bacterial cultures, no gradual adaptation to acid environments could be observed. The survival studies were carried out at 30 degrees C.