Ecology of accelerated natural lactic fermentation of sorghum-based infant food formulas

Accelerated natural lactic fermentation of mixed sorghum-cowpea (Formula 1) and sorghum-milkpowder (Formula 2) infant food formulas was achieved by repetitive (60 fermentation cycles of 24 h each) use of the previous batch as an inoculum at a rate of 10% (w/w) and resulted in a gradual establishment of mixed populations of lactic acid bacteria and yeasts. In Formula 1, early fermentation stages (fermentation cycles 1-4) were dominated by Leuconostoc and Lactococcus spp. which caused conditions inhibitive to yeasts. Probably due to micronutrient deficiencies, the former lactic acid bacteria were succeeded by a combination of Lactobacillus plantarum and Candida spp. achieving pH values 4.2-4.3. In formula 2, Lactobacillus acidophilus, Lactococcus lactis and Lactobacillus brevis consistently achieved pH 3.7-3.8, thereby allowing only a minority of yeasts, mainly Candida and Trichosporon spp. None of the isolated yeasts exhibited 'killer'-activity.