Prebiotics are a group of nondigestible carbohydrates that promote the growth of healthy bacteria in the human gut. In recent years, major infant formula brands have added prebiotics to their lines to promote baby’s digestive health, while most yogurt manufacturers have eliminated prebiotics from their product formulation.

Sourcing novel prebiotics

Traditional criteria to qualify an ingredient as a prebiotic include: resistance to digestion in the stomach and small intestine, ability to be fermented by intestinal microflora and capability to selectively stimulate the growth of beneficial bacteria. Prebiotic ingredients which meet these criteria that have been widely used by the food industry include galactosaccharides (GOS), and the inulin-type fructans including the subcategory of fructooligosaccharides (FOS). Other prebiotics include lactulose, polydextrose, human milk oligosaccharides (HMO) and resistant corn starch.

Emerging prebiotics include fibers present in whole grains and pectins.

“One example is a stabilized rice bran that is currently being used in a rice milk yogurt,” said Mark McKnight, vice president of sales and marketing at RiceBran Technologies.

There is also interest in beta glucans and arabinoxylans. Some of these ingredients will be more difficult to commercialize than others.

“While some prebiotic ingredients might deteriorate or cause color change in certain beverage systems, polydextrose performs well in shelf-stable dairy beverages,” said Ramon Espinoza, product specialist, DuPont Nutrition and Health, New Century, Kan.

“Prebiotics were initially defined in 1995, and that definition has been the subject of some good scientific debate,” said Bob Hutkins, professor of Food Science, at the University of Nebraska.

Components of many common foods, including phenolic compounds associated with wine or berries, can influence the gut microbiota. However, there is no evidence that these components are fermented or metabolized by healthy gut bacteria, and so they don’t fit in the current definition of prebiotics. Also, some prebiotic fibers promote the growth of beneficial bacteria other than Bifidobacterium and Lactobacillus species, and so they would potentially qualify as prebiotics.  

Infant formula

Oligosaccharides are found naturally in breast milk, and the infant formula industry is adding GOS and FOS, primarily from plant sources, for their prebiotic effect. Recently, a novel enzyme that cleaves specific glycans from milk proteins was identified in Bifidobacterium infantis.

“We successfully expressed this enzyme in host organisms, and scaled up enzymatic cleavage of complex glycans in whey proteins in our dairy pilot plant. Initial growth data revealed that these glycans are specific prebiotics and enable the growth of B. infantis but not B. lactis,” said Daniela Barile, PhD, associate professor, Foods Science & Technology, University of California, Davis. “These exciting results suggest that glycans released from dairy proteins are selective prebiotics, producing a similar growth phenotype to the gold standard, human milk.”

The ability to use novel processing enzymes to harvest bioactive HMO mimics (glycans from proteins) using an abundant and inexpensive substrate such as cheese whey, will expand their use in gut health applications.

Prebiotics, obesity

Emerging research for prebiotic ingredients focuses on their potential role in influencing obesity.

“To date much of this research has been conducted in animal models, but a few small studies have shown effects in humans. Some interesting work is being conducted by Patrice Cani and Nathalie Delzenne at the Université Catholique de Louvain in Belgium,” said Mary Ellen Sanders, PhD, of Dairy and Food Culture Technologies, Centennial, Colo.

 Work at this university is exploring the potential role of prebiotics on hepatic insulin resistance, gut peptides and appetite regulation, and low-grade inflammation as it relates to obesity.

Challenges of clinical research

Regulatory guidance, both from EFSA and the FDA, has forced ingredient manufacturers to change the way they conduct clinical research.

“DuPont is currently conducting clinical research on soluble dietary fibers and their prebiotic effect. Clinical trials are more expensive because they must include more individuals and they must involve healthy people. For example, digestive and transit studies would include individuals with a tendency toward slow transit,” said Espinoza.

 Without a structure-function claim, it’s difficult for dairy manufacturers to justify the cost of adding a prebiotic ingredient to their formulation. But as new clinical research substantiates the health benefits of prebiotics, expect usage of prebiotics to rebound in dairy products.