A very promising alternative increasing in application in food products in the U.S. and Europe is the use of prebiotics. Prebiotics are non-digestible carbohydrates, usually oligosaccharides, which survive digestion in the stomach and small intestine and enter the colon. The important feature of prebiotics, however, is that they are then selectively fermented by the indigenous “probiotic” bacteria, increasing their population and activity. The ingestion of prebiotics has repeatedly been shown to alter the composition of fecal bacteria. Generally, a positive effect would be to see increases in the populations of lactobacilli and bifidobacteria and decreases in less desirable organisms such as clostridia and protein-degrading bacteroides. These organisms produce toxins and tumor-promoters from metabolism of proteins that have escaped digestion in the upper gut. On the contrary, bifidobacteria and lactobacilli produce a complex range of compounds which inhibit the growth of invading pathogens. They also are capable of modulating the activity of the immune system.
In the U.S. and Europe, there are a limited range of prebiotics available for use in food processing. These include fructans and galacto-oligosaccharides. The fructans are either inulin, derived from chicory, or fructo-oligosaccharides (FOS). FOS can be made from chicory inulin by partial hydrolysis or from sucrose by enzyme transfer reactions. Galacto-oligosaccharides (GOS) are manufactured from lactose by enzyme transfer reactions and thus represent a potential economic upgrading of a by-product from the dairy industry. The disaccharide lactulose is also a prebiotic at sub-laxative doses. It is not, however, used in foods at the present time, presumably as it commands a higher price as a medicine for treatment of constipation and hepatic encephalopathy.