Effect of bifidogenic factors on growth characteristics of bifidobacteria in infant formulas.

A bifidogenic factor, lactulose or fructooligosaccharides, was added (0.5%) into infant formula based on soy or infant formula with hydrolyzed casein. The infant formulas were then inoculated (2.5%) with Bifidobacterium bifidum (ATCC 15696), Bifidobacterium breve (ATCC 15700), Bifidobacterium infantis (ATCC 15697), or Bifidobacterium longum (ATCC 15708) or their mixture (mixed culture) and incubated at 37 degrees C for 24 h. Lactulose did not influence maximal counts or generation times in either formula for any species except B. infantis, which had lower counts. Trends of developed acidity and pH of the mixed culture in the infant formulas with or without lactulose were similar to those for B. breve. Maximal counts and generation times remained unchanged with or without fructooligosaccharides for all species and the mixed culture, except for B. bifidum in the formula based on soy, for which maximal counts did not occur. Growth in either formula was inhibited for B. infantis with lactulose and B. breve with fructooligosaccharides past 8 h of inoculation.