Prebiotics are basically non-digestible food ingredients that can benefit the human body by stimulating the growth and activity of beneficial bacteria -- also known as probiotics -- in the colon. A more precise definition by the International Scientific Association of Probiotics and Prebiotics (ISAPP) is “a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health.”
Although prebiotics are mainly known to have an effect on colon microbes, some scientists think they may interact with other systems, such the oral cavity and the uro-genital tract. There is potentially a great number of substances that fulfill this role. Some examples are inulin from chicory and Jerusalem Artichoke, short chain fructo-oligosaccharides (short-chain FOS) and trans Galacto-oligosaccharides (T-GOS). It is very important that the effect of prebiotics is scientifically proven prior to making any claims.
Friendly bacteria known as probiotics ferment the prebiotic substances in the large intestine and produce short chain fatty acids (scFAs). These fatty acids decrease the colon pH. Lowering the pH of the colon assists in the reduction of pathogenic bacteria and viruses, thus reducing the incidents of diarrhea and other problems associated with infections of the gut. The scFAs are absorbed into the blood stream and metabolized by the body. The activity of the beneficial bacteria and the various substances they produce in the large intestine also is thought to contribute to numerous health benefits, ranging from prevention of chronic diseases to improving the immune system, as well as facilitating the absorption of minerals and vitamins into the body.
Due to consumers’ sometimes-unhealthy diets, these bacteria tend to diminish to such an extent that they are not present in sufficient numbers to provide a beneficial role. The numbers of these microorganisms in the colon can be increased in three ways. First is a diet change, to consume more foods that contain prebiotics so that these bacteria naturally re-establish normal populations in the colon over time.
Second, high doses of probiotics may be taken orally; these should be consumed regularly to have a beneficial effect. A substantial number of these bacteria will survive the harshness of the human digestive system, and an essential number will end up in the colon, where they will get established and eventually provide the health benefits. Taking probiotics orally needs to be accompanied by having enough prebiotics in the diet for the bacteria to feed on in order to survive, flourish and produce the substances that provide the health benefits.
A third approach is to take prebiotics and probiotics in combination as a food. Although this practice is known to many cultures of the world, it is only now beginning to be appreciated in North America. For example, a live-culture yogurt will contain both prebiotics and probiotics. Food companies are developing many new products that contain prebiotics, probiotics or both.
[Editor's note: It has also been argued that increased consumption of probiotics will selectively support naturally present (i.e., endogenous) probiotics, thus increasing their level over time.]
Adding Prebiotics and Probiotics to Foods
Incorporating prebiotics into food products is a natural way to deliver these healthy ingredients to consumers. Most prebiotics are easy to incorporate and, as an added bonus, are instrumental in providing functionality to the food product. For example, short-chain units of prebiotics will behave like sugar and contribute to the browning effect and crispiness of the finish product. On the other hand, longer-chain unit prebiotics will act like a fat replacer, contributing to texture and mouthfeel. Most prebiotics are not normally damaged or substantially altered by food processing conditions, and therefore, their gut functionality is retained. On the other hand, harsh processing conditions will kill the majority of probiotics in prepared foods, since food processing parameters are often designed to eliminate microorganisms for food safety reasons.
New technologies may provide tools that could partially overcome this problem. Cultures of probiotics are now available in microencapsulated form that is designed to survive the intestinal environment and reach the colon unharmed. These encapsulation techniques may also provide a viable solution for the incorporation of these bacteria in processed foods. In addition, some of these bacteria form spores when they are exposed to high temperatures. The spores can survive high temperatures for long periods of time. Perhaps delivering these bacteria in the form of spores could be another solution.
Many opportunities await the food processing industry to develop food products that contain prebiotics or probiotics. Before developing these products, it is important to make sure they comply with the regulatory requirements of the country in which they are produced, marketed and exported.
Both prebiotic and probiotic applications to processed foods need to be approached with caution. Food industry innovators need to make sure that the products developed are truly delivering the beneficial effects to the consumer. Prebiotics and probiotics are incorporated into food products to provide health benefits to the consumer. It is important that these benefits are maintained through the manufacture and storage of the product until they are consumed.
From the December 6, 2010, Prepared Foods E-dition