Quantify activity of commercial prebiotics.

Prebiotic bacteria are functional food ingredients that are neither digested nor absorbed in the human digestive system. But they stimulate the growth of specific intestinal microorganisms. Probiotics are small organisms that help maintain the natural balance of organisms--microflora--in the intestines.

Methods for assessing the extent to which a prebiotic stimulates the growth of probiotic organisms reportedly do not exist. Such a technique would provide a basis for optimizing combinations of prebiotics and probiotics. Scientists at the University of Nebraska wanted to establish a prebiotic activity assay and determine the activity score of five commercial prebiotics. Their research has led to the development of a quantitative method for evaluating the ability of commercial prebiotics to selectively stimulate various probiotic bacteria. Information gained from this research will aid in the optimization of probiotic and prebiotic combinations as functional food ingredients.

Investigators based prebiotic activity scores on the change in cell biomass obtained after growth of the probiotic strain on 1% prebiotic or 1% glucose, and after 24 hours relative to the change in cell biomass obtained for enteric strains grown under the same conditions. Prebiotic activity was measured for five commercial prebiotic carbohydrates: two forms of fructooligosaccharides, two forms of inulin and a purified form of galactooligosaccharides. Activity also was determined for 10 probiotic bacteria: five Lactobacillus and five Bifidobacterium.

Prebiotic activity scores were dependent on the probiotic strains tested and the type of prebiotic utilized. The highest scores were for Lactobacillus paracasei 1195, which was paired with the two inulin products and one of the fructooligosaccharides (1.17, 1.10 and 1.00, respectively). In contrast, B. bifidum NCI had the lowest scores when grown on galactooligosaccharides and inulin (-1.24 and -1.17, respectively).

Most potential prebiotics are carbohydrates, but the definition does not exclude non-carbohydrates that could be used as a prebiotic. In theory, any antibiotic that would reduce the number of potentially harmful bacteria and favor health-promoting bacteria or activity can be considered a prebiotic.

Further information. Robert Hutkins, Department of Food Science and Technology, 338 Food, University of Nebraska, Lincoln, NE, 68583; phone: 402-472-2820; email: rhutkins1@unl.edu.