Intestinal flora may not be the first topic that springs to mind during high tea. Mainstream foods designed to improve gut health have, however, lessened the stigma of discussing what’s going on with what’s going in. Consumers are steadily becoming more aware of beneficial bacteria such as Lactobacillus and Bifidobacterium, as well as some strains of Streptococcus thermophilus, Escherichia, Enterococcus and Bacillus. Strong enough to survive the journey through our digestive system, and powerful enough to provide an array of healthful benefits, these important microorganisms cannot live without nutrition. Such nourishment comes in the form of prebiotics.
Bacto-snacks
Prebiotics are dietary carbohydrates. Although typically some form of fiber, not all fibers are prebiotics. Classification as a prebiotic requires resistance to digestion and absorption in the gastrointestinal tract, fermentability by gastrointestinal microflora, and stimulation of growth or activity of one or more beneficial intestinal bacteria.
Prebiotics are also not universal in their usage by bacteria. Larger particle sizes can inhibit fermentation by certain bacteria. Byprod-ucts of fermentation by one bacterium, however, can feed another. Differences also exist in the overall health benefits provided by pre-biotics. In addition to proliferation of helpful bacteria, prebiotics have demonstrated positive effects such as improved mineral absorp-tion, reduced risk factors for colorectal diseases, improved immune system function and improved resistance to infection.
Prebiotic parade
Utilized as a bulking agent, and for fat and sugar reduction, polydextrose has gained recognition as a prebiotic fiber. Polydextrose is an oligosaccharide—a short chain of sugar molecules (typically 3 to 10 units) made by thermal polymerization of glucose. It imparts greater viscosity than sugar at the same concentration, but does not deliver tremendous sweetness. Although partially hydrolyzed in the small intestine, low-molecular-weight polydextrose polymers are fermented by probiotic organisms in the gut, yielding short-chain fatty acids (acetate, butyrate and isobutyrate) that help retard development of colon cancer.
Polydextrose is water-soluble and has a neutral flavor. While only mildly sweet, it can help balance the sweet taste of high-potency sweeteners, and mask off-flavors of fortification ingredients, such as some vitamins and minerals. It is easily incorporated into beverage products, and stable under UHT and pasteurization processes at 3 to 7 pH. In ice-cream, polydextrose provides freezing-point-depression effects similar to that of sugar. It improves humectency and shelf life in baked products and bars.
Many plants, such as onions, Jerusalem artichokes and chicory contain inulin, a family of fructose polymers ranging from 2 to 60 fructose units, but typically greater than 10. Fructooligosaccharides (FOS) are chains with 10 fructose units or less, and are 100% fer-mentable. The smallest of these, 2 to 4 fructose units long, are referred to as short-chain fructooligosaccharides (scFOS). Their actual degree of fermentation depends on the bacterial strain.