Research is uncovering the importance of gastrointestinal (GI) health. Beyond simple digestive regulation and avoidance of unpleasant disturbances, some benefits include increased immune defence, enhanced nutritional absorption, lessened reactions to allergens and improved oral hygiene, cholesterol and weight management. Consumers are becoming increasingly aware of the need to not only feed their stomachs but to feed their GI systems.
The food industry is discovering new ingredients as a means to feed and support healthy digestion. Probiotics and prebiotics are appearing in products found in the dairy case, the frozen food section, the cereal aisle, the candy counter and in just about any imaginable vehicle.
Digestive EcosystemThe digestive system is teeming with bacteria in a climate that is as complex and succinctly balanced as the densest jungle. Trillions of bacteria, including hundreds of species, must exist in perfect balance for ideal health. Probiotics and prebiotics can play an important role in this delicate balance.
Probiotics are defined as live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. Microbial equilibrium is always at risk because the GI lining is replaced every week or so. A healthful diet is necessary both to replenish probiotic bacteria and also to nourish them.
Prebiotics are selectively fermented ingredients that essentially ‘feed’ the healthy bacteria, that is to say, allows specific changes in the composition and/or activity of the GI microflora in a beneficial way. The type and amount of prebiotics consumed influences the microbial population and the types of bacteria that inhabit the GI tract.
ProbioticsProbiotics may be the answer for healthy digestion, but successfully incorporating them into finished products can be quite difficult. Live probiotic bacteria must withstand processing, storage and transit to the human GI tract and they must survive in reliable numbers to meet labelling claims.
In addition, probiotic definitions and health may vary among countries which can add to the complexity of incorporating these into foods. Table 1 shows an example of claims accepted by Health Canada in regards to probiotic microorganisms in food.
The Joint FAO/WHO Working Group Report on Drafting Guidelines for the Evaluation of Probiotics in Food offers guidance for the evaluation of probiotics in food.
The group stresses strain identity distinguished by current scientific names. Probiotic effects are predominantly strain specific, with a few possible exceptions. It stands to reason that a health claim should correlate the health benefits linked to specific strains.
Besides genus, species and strain designation, the minimum viable numbers of each probiotic strain at the end of the shelf-life should be declared on products making probiotic claims.
Laboratory TestingLaboratory testing is essential to all phases of product launch—development, pilot plant, shelf-life testing and ultimately manufacture, to be sure that sufficient levels of probiotics are maintained. Knowing the optimum point for addition of probiotics into the manufacturing process is key to maximising viability.
Temperature, pH and shear can impact the ability of probiotic bacteria to not only survive, but to flourish. Oxygen exposure, during manufacture or through permeation through packaging, also affects probiotic viability.
Testing may not only be necessary for finished products, but also to ensure the quality of incoming goods is monitored and sustained. In addition, proper storage conditions must be utilised to preserve shelf-life of these probiotic bacteria.
To accurately enumerate bacteria, it is necessary to use specific methodology based on the strain. These methods are based on antibiotic resistance, the sugar fermentation abilities of the different strains, oxygen requirements and whether or not they are present as spores.
When multiple species are present within a given product, enumeration procedures are especially complex and may require different media than would be used if targeting a single bacterial strain.
As an example of the complexity of probiotic testing, 19 different media are can be used to differentiate the different species of lactobacillus in commercial samples.
Providing protection for probiotics at the start of their journey to food manufacture and ultimately digestion is key to maximising survivability.
MicroencapsulatingEntrapping cells with a calcium-alginate gel matrix is the most common method of microencapsulation. Spray drying, extrusion and emulsions are also means of microencapsulating live cells with a physical barrier.
Yet microencapsulation is not without challenges. All ingredients must be affordable, compatible and food grade. Microencapsulated probiotics must not have a deleterious effect on flavour or texture. The microencapsulate must offer sufficient protection during manufacture, storage and digestion.
In the end, they must be able to release the probiotic bacteria at the targeted point in the GI tract. There is a great deal of innovation in finding the best possible combination of cost, ingredient, process and microbial advantage.
A wealth of imaginative delivery systems is quickly reaching consumers, including beverage caps and straws. One product incorporates a healthful blend of probiotics, antioxidants and prebiotic fibre and stores them in the bottle cap.
The ingredients are released into 12 ounces of water when a button is pressed. Another product incorporates dry, stable probiotics in beads that are cradled in filters at both ends of the straw. As liquid passes through the straw, the beads dissolve and release the probiotics.
PrebioticsIn order to boost populations of beneficial bacteria in the GI tract, it is helpful to provide a food source and prebiotics do just that. They are non-digestible and like probiotics, must confer health benefits to the host.
The most commonly used prebiotics are inulin-type fructans. Fructan is a general term used to describe chains of fructose molecules with anywhere from two to 60 units connected with beta (2-1) fructosyl-fructose glycosidic bonds.
Fructooligosaccharide (FOS) or oligofructose is a more specific term that can be used to describe short chains of fructose with two to 10 units, whereas inulin generally refers to compounds having greater than 10 units.
Inulin chains are usually terminated but a glucose unit, whereas FOS may or may not as this is dependent on how the FOS is produced. Many plants and vegetables, such as artichokes, leeks, asparagus, onions, garlic and chicory, contain these inulin-type compounds.
Galactooligosaccharides (GOS) are another group of commonly used prebiotics. Like oligofructose and inulin, they stimulate species of bifidobacterium, and to a lesser extent, lactobacilli. GOS is structurally similar to oligosaccharides that occur naturally in human milk, and offer similar health benefits.
Other less studied candidate prebiotics include polydextrose, soybean oligosaccharides, isomaltooligosaccharides, glucooligosaccharides, xylooligosaccharides, palatinose, gentiooligosaccharides and sugar alcohols, such as lactitil, sorbitol and maltitol.
Evaluation & StandardsWith such a wide range of emerging chemical compounds and attributes, organisations such as FAO Food Quality and Standards Service and International Scientific Association for Probiotics and Prebiotics (ISAPP) are calling for scientific evaluation of functional and health properties.
Figure 1 shows example guidance for evaluation and substantiation of prebiotics. Regulatory standards may be lacking, and many of the newer compounds have been used in animal studies. but not human research.
Some potential prebiotics are described by ISAPP as ‘candidate’ prebiotics, since scientific evidence is less advanced. Well-conducted human trials are required to substantiate claims.
ISAPP stresses that the term prebiotic should be confined to nutrients that are selectively fermented only by beneficial digestive microflora. Oligosaccharides non-selectively fermented in the colon may have been erroneously described as prebiotic.
This classification is inaccurate since the prebiotic definition applies only if a small number of beneficial bacteria ferments the prebiotic, and not a large number of microbes with potentially generating negative health effects.
FAO provides three criteria for qualifying prebiotics. Foremost, a prebiotic is not an organism or a drug but is a component that can be characterised chemically. Second, it must have a measurable health benefit that is not due to absorption of the component into the bloodstream or due to the component acting alone.
Last, it must be shown that the sole presence of this component and the formulation in which it is being delivered changes the composition or activities of the microbiota in the target host. FAO suggests these mechanisms might include fermentation, receptor blockage or others.
Health ClaimsMeeting health claim approval is less concrete than meeting nutritional label claims. Not only do health claim labelling laws differ among countries (as do nutrition labelling laws), but health claim laws are often ill defined. Companies must be able to defend their positions with clinical studies.
European Union regulations stipulate that nutrition and health claims must be based on and substantiated by generally accepted scientific data.
What a manufacturer considers ‘generally accepted scientific data’ may be completely different than that of a regulator, leading to an unapproved request. In the last few years, European Food Safety Authority (EFSA) has generated guidance documents for the scientific requirements for certain health claims, and this should help companies plan submissions accordingly.
In Canada, probiotic health claim compliance has been required since April 2010, a year after publication of their Accepted Claims About the Nature of Probiotic Microorganisms in Food.
This guidance document provides an explanation about the requirements necessary for health claim uses and helps companies understand the regulations.
Undoubtedly, it will take time for legislation across the globe to catch up with rapidly developing ingredient advances and new product introductions, to say nothing of the scientific studies illuminating new health benefits.
Finally, genomic research projects have explored the notion that probiotic nutritional input can be targeted to specific genetic make-up to optimally impact health. Dialling in probiotics based on a personal genotype may ultimately provide the answer that leads to greater longevity.