Food Product Design: Health/Nutrition - May 2005 - Synbiotic Synergy of Pro- and Prebiotics

May 2005

Synbiotic Synergy of Pro- and Prebiotics

By Sharon Gerdes
Contributing Editor

Americans are a little behind Europeans and Japanese when it comes to understanding the importance of gut health. But that might be changing. It appears that some of the European enthusiasm for probiotics might be crossing the big pond and reaching Americans. Probiotics literally means, "good for life," and new product data from New York-based Datamonitor's NPD database, ProductScan Online, show that probiotics are among the top food trends for 2005, so they may also be "good for business."

Prebiotics are the food or fuel for these healthy bacteria. Studies show that the consumption of a wide range of prebiotics can improve gut health, even when no probiotic is present. However, when a food formulator can combine both into one food, the result is called "synbiotic," and that might just be the next hot food trend.

A wealth of scientific evidence is emerging to show that probiotics and prebiotics might enhance a number of normal functions while playing a role in reducing the risk of several chronic diseases. Food manufacturers and industry associations are also making a major effort to inform consumers and health professionals about the many benefits of probiotics and prebiotics. First let's explore the health benefits of probiotics.

Friendly bacteria
The most-compelling health benefit of probiotics is their effect on balancing intestinal microflora. Probiotics are defined as live microbial food supplements that benefit the host by improving the microbial balance in the intestine. Jim Kopp, vice president, Lallemand Advanced Baking Solutions, Montreal, explains their activity in a way that typical consumers can understand: "Probiotics take up space in the large intestine. When that space is filled with healthy, beneficial bacteria, it keeps out the pathogenic bacteria. These healthy, beneficial bacteria increase the health of the digestive tract."

The bad bacteria can proliferate in the digestive tract because of various factors, including diet, stress and antibiotics. A typical American diet, high in fat and low in fiber, might contribute to this imbalance.

The Third International Convention of Probiotics was recently held in Paris, bringing together researchers and health professionals from around the world to uncover new facts about the role of probiotics in good health. "There is consensus that probiotics help to minimize the effects of lactose intolerance," notes Miguel Freitas Ph.D., medical marketing manager, The Dannon Company, Inc., White Plains, NY. "These lactic-acid bacteria will actually predigest the lactose, metabolizing it to lactic acid. The probiotic bacteria in fermented-milk products and yogurt that survive the trip to the intestinal tract may also provide additional lactase-enzyme activity. This is why it is easier for certain population groups to digest yogurt than it is to digest milk."

Newer research shows that probiotics can provide benefits to the entire body, from oral health to colon health, according to Mary Ellen Sanders, owner Dairy & Food Culture Technologies, Centennial, CO. "One of the best substantiated benefits of certain probiotic strains is their ability to reduce the duration of infectious diarrhea (often caused by rotavirus) in infants and children. The impact on reduction of incidence is less well documented. Some studies have shown a reduction of incidence of antibiotic-associated diarrhea and travelers' diarrhea, but not all studies are positive. This likely suggests the importance of choosing the right strains and doses for efficacy."

Probiotics also help to improve immune function. "A recent Dannon survey indicated that nearly a third of Americans are very concerned about the strength of their immune system, yet 65% did not know the beneficial effect of probiotics on immunity," according to Freitas. About 70% of the body's immune system is located in the intestinal tract. Research shows that probiotics might have a beneficial impact on the regulation of critical components of the immune system, such as antibodies and natural killer cells.

Finally, a growing body of evidence is indicating that probiotics might have a role in minimizing the risk of several diseases including intestinal infection and Helicobacter pylori. "While more clinical trials are warranted in these areas, the initial research shows promise in both irritable bowel syndrome (IBS) as well as inflammatory bowel disease (IBD)," adds Freitas. "The case is also strong for reducing allergies and eczema in children." Currently, there is no consensus on reducing the risk of colon cancer, but this is certainly an area of keen interest.

It must be noted that specific health benefits are derived from specific bacteria. Some of the strains with documented health benefits include members of the Lactobacillus genus (L. casei, L. acidophilus, L. plantarum, L. rhamnosus, L. paracasei) and bifidobacteria (B. bifidum, B. lactis). For example, L. casei has been shown to strengthen the body's defenses.

"Danisco has an excellent range of probiotic cultures with documented health benefits marketed under the FloraFIT(TM) and HOWARU(TM) brands," notes Beth Jones, product manager, cultures, fresh dairy and probiotics, Danisco USA, Madison, WI. "Also important is the quality of documentation and safety. Danisco has over 20 gold-standard clinicals with their strains, and strains demonstrating safe use for over 15 years in the industry."

Many manufacturers add a combination of one or two bacteria. But one manufacturer combines three bacteria in an encapsulated form. The goal is to deliver these healthy bacteria "alive" to the colon where they do their magic.

Staying alive
Different probiotic cultures have different survival rates, and good survival is a selection criterion for probiotic cultures. Probiotic bacteria must first remain viable through the shelf life of the product. Then the probiotics must survive the treacherous journey through the acidic environment of the stomach, past the bile juice secreted by the pancreas and ultimately into the colon.

The way to deliver viable probiotic cultures in a food system, dairy or nondairy, is to keep the cells in a semidormant, nonmetabolizing state. "This is achieved by either keeping the food refrigerated, maintaining a low-moisture environment in the food or creating a moisture barrier between the culture and the food matrix," says Jones. "Yogurt is the best example of a probiotic-supplemented food employing low temperature to preserve probiotic viability. Low-moisture powdered beverages offer a means to preserve probiotic viability in a dry-food format. Both of these approaches to maintaining viable probiotic cultures are well used in the food industry."

The pH of the food can also impact probiotic viability. "Maintaining the pH in a range that the culture normally sees during fermentation is best, and generally falls in the pH range of 4 to 7.5," says Jones. "Select organisms may be able to tolerate pH outside of this range, but this is a good range to start with when formulating a probiotic-supplemented food."

Another formulation approach is to create a moisture barrier or use microencapsulation. "Microencapsulation will allow supplementation of probiotics into moist food systems, such as bars in which refrigeration is not utilized," explains Jones. "This technology is exciting for food formulators as it will open doors to a multitude of new probiotic delivery vehicles. Probiotic cultures are living organisms, thus elevated temperatures above normal ambient temperatures can be detrimental and should be avoided. Baking temperatures or pasteurization temperatures will be lethal to cultures. So the addition of cultures to a food must be completed after all heat treatments."

In yogurt, there are standards for levels of live and active cultures. However, there are no standards for levels of viable probiotic bacteria in other food products. "One possible target level is 5 million active bacteria per serving of food," suggests Kopp. "When the probiotics are in the body, the objective is to have 0% release in the stomach and 100% release in the lower intestine." That is where the prebiotics become critical.

Bacterial chow
The term "prebiotic" is used to describe a variety of oligosaccharides and other food ingredients that promote the growth of beneficial organisms. The fermentation of prebiotics produces short-chain fatty acids. Their presence reduces colonic pH, which inhibits growth and activity of pathogens. In the United States, the most widely used prebiotics are fructans, inulin and oligofructose (also known as fructooligosaccharides, or FOS), a widely used source of prebiotics that comes from chicory and Jerusalem artichoke plants.

Various lactose derivatives, such as lactulose, lactitol and lactosucrose, also function as prebiotics. Tagatose, a newer, multipurpose, low-calorie bulk sweetener derived from lactose, can also function as a prebiotic. Processors can also derive prebiotics from starch. This group includes malto- and isomalto-oligosaccharides, polydextrose, and certain resistant starches. Gums can also serve as prebiotics.

Armed with an understanding of the health benefits of each prebiotic, product designers can then see how they can incorporate the various probiotics and prebiotics into winning food formulations.

Bring on the inulin
As mentioned above, currently the two most widely used prebiotic ingredients are inulin and oligofructose. The primary difference is that FOS contains short chains of between 2 and 10 fructose units. The term "inulin" describes a broad range of fructans, including chains of 2 to 60 units.

Both ingredients behave the same nutritionally. They both are considered fiber, and both might help to reduce the risk of cardiovascular disease by reducing serum cholesterol. "Both ingredients boost immunity and have no affect on blood glucose," notes John Martin, project leader, Orafti Food Ingredients, Malvern, PA.

Inulin might also have potential for reducing the risk of colon cancer. "A recent EU-sponsored multi-center study showed that several bio-markers for colon cancer risk were positively modulated by a synbiotic treatment consisting of inulin and probiotic bacteria," notes Fred Kaper, board member, Sensus America, Monmouth Junction, NJ.

A recent clinical trial showed that consuming 5 grams per day of Frutafit® inulin for 90 days resulted in a significant increase in bifidobacteria. "This paper has been submitted for publication in the European Journal of Clinical Nutrition," adds Kaper. This represents the first time that a dose-response effect of a prebiotic formulated in a processed food product was investigated and demonstrated in vivo in healthy human volunteers.

Research has shown that adding a combination of short- and long-chain fructans can increase calcium absorption by 18%. Generally, short-chain units are broken down in the first part of the large intestine, while the longer-chain units are broken down in the lower part of the large intestine. This digestion through the colon increases the absorption of calcium and magnesium by the body.

Recent science indicates a positive interaction between short-chain FOS (scFOS(TM)) and isoflavones on bone-mineral density. "The preliminary research is promising, and human work is in progress," says Linda C. Douglas, scientific affairs manager, GTC Nutrition, Golden, CO. "These findings are very exciting, given the ability of scFOS to stimulate calcium absorption. In addition, there is a wealth of evidence to support gut health. More recently, scFOS has been shown to reduce the symptoms associated with irritable bowel, provide probiotic support versus broad-spectrum antibiotic use and increase the effectiveness of lactobacilli in the body."

A hefty dose
Another prebiotic ingredient, polydextrose, beneficially provides sustained fermentation throughout the   colon. "The rapid fermentation of fast-fermenting prebiotics with subsequent gas production and accumulation of lactic acid in the proximal part of the large intestine can cause gastric discomfort," notes Donna Brooks, product manager, Danisco Sweeteners, Ardsley, NJ. "Slowly fermented prebiotics, such as polydextrose, can sustain fermentation all the way to the distal end of the large intestine. This result is less gas and no lactic-acid accumulation, thus minimizing gastrointestinal stress."

Unlike some prebiotics, polydextrose is tolerated up to a mean dose of 90 grams per day with no adverse gastrointestinal effects. A comparative study showed that a diet with supplemental Litesse® lowered the fecal pH and reduced the production of some carcinogens. Polydextrose is 90% prebiotic.

How low can you go?
Another effective prebiotic is resistant starch. "Most starches are digested and absorbed in the small intestine, but resistant starch passes through to the large intestine where it functions as a dietary fiber," notes Rhonda Witwer, business development manager, nutrition, National Starch Food Innovation, Bridgewater, NJ. "There are different types of resistant starches in the diet. RS2 is a type of resistant starch that retains its natural granular shape, but resists digestion because of crystallinity within the granule. This particular resistant starch functions well as a prebiotic."

Studies in rats, pigs and various other animals have shown that high-amylose resistant starch increases the number of beneficial bacteria and decreases the number of harmful bacteria in the colon. "Specifically, RS2 increases bifidobacteria and lactobacillus and decreases E. coli," adds Witwer. "Selected strains of bacteria have been shown to bind to the starch granule all the way to the large intestine."

Studies show that most people need 15 to 20 grams of fiber per day. Most get 4 to 5 grams a day from bread, corn, cereals and beans. An additional 10 to 15 grams per day of resistant starch would be needed in the diet to derive the full range of health benefits.

Resistant starch increases the production of butyrate in the colon. Studies indicate that butyrate may be protective against colon cancer, and is the preferred energy source for colon cells. A 2003 study, published in Microbiology and Immunology (Vol. 47, No. 12), showed that a combination of Hi-maize(TM) and Clostridium butyricum, a probiotic strain of bacteria, significantly decreased the number of aberrant crypt foci, a precursor and biomarker for colon cancer, more than the probiotic alone.

In the dairy case
Traditionally, probiotics have been delivered in yogurt and other cultured dairy beverages. "Lactic acid bacteria (LAB) got their start with dairy products as a means to add shelf life to milk," notes Joe O'Donnell, executive director, California Dairy Research Foundation, Davis. "Over the ages, the LAB have grown quite comfortable living in the milk environment. Product developers have exploited that relationship and developed all kinds of fermented-dairy products."

Those LAB that produce health (probiotic) benefits also enjoy a relationship with the milk environment. LAB receive messages from the milk. "We don't know a lot about how milk guides the probiotics, but we will," adds O'Donnell. "It is because of this interaction that milk is the preferred delivery vehicle for most probiotics. Milk is not only providing a substrate for the bugs, but is indirectly influencing growth and development and health of the consumer. Nature was very clever by working with systems rather than individual foods."

Probiotics should be consumed on a regular basis to have a beneficial effect. One method of delivery is through daily probiotic servings, sometimes referred to as "shots." A new report from New York-based market-research publisher Packaged Facts, "The U.S. Market for Cultured Dairy Products," released in Feb. 2005, shows that daily probiotic servings are becoming increasingly popular in the United States. These concentrated probiotic beverages are often sold in small, single-serve bottles averaging just over 3 oz. each. "A typical 100-ml probiotic serving sold in the supermarket will contain 10 billion L. casei Defensis(TM) bacteria," adds Freitas. "The manufacturer has conducted quality-assurance tests to ensure that these numbers of viable bacteria are available for the typical 27 days of shelf life." It should be noted that this product is being sold as a food, and not a dietary supplement.

Prebiotic inulin also provides a number of formulation benefits to various dairy products. Inulin functions well in chocolate milk, often in combination with carrageen. It can help improve the mouthfeel of nonfat and low-fat products at a usage level of 1% to 5%. In soymilk products, inulin can help to mask any undesirable flavor notes.

Kaper notes that inulin also functions as a fat replacer in low-fat cheese. In processed cheese, it can aid in fat reduction at a level of 3% to 5%. In cream cheese, it improves spreadability at a level of 9% to 15%. In hard cheeses, it can help reduce caseinate and starch levels. He also comments that in fresh cheese, inulin binds water and limits water loss in cooking. In ricotta cheese, inulin can replace guar and karaya gums, which are much more expensive.

Yogurts and smoothies
Since dairy products have a high buffering potential in the stomach, the result is a protective effect on the good bacteria. During fermentation, cultures may produce additional bioactive components and functional peptides, which have additional health benefits. Thus, all types of yogurt and dairy smoothies are good vehicles for probiotics. "Inulin works well in drinkable yogurt where it adds mouthfeel, creamy texture and reduces fat," comments Martin.

Inulin can also help stabilize beverage systems. The longer-chain inulin works well in systems that are already cloudy and where a thicker product with creamier mouthfeel is desired. Food formulators can easily incorporate 2.5 grams per serving in these products to achieve a "good source of fiber" claim.

Short-chain inulin is also available as a liquid product. "This product can be shipped in totes and is easily dosed into dairy products or beverages," notes Kaper. "Inulin syrup is very soluble up to 75%." The viscosity and sweetness is comparable to that of maltitol syrups or a DE 60 corn syrup. The water activity is also the same as maltitol syrups.

"Resistant starches are insoluble, and so they work well in thickened beverages where the texture of the beverage helps hold the starch in suspension," comments Witwer. "Resistant starch is also being used in yogurts, where 2 to 3 grams can be used in a typical yogurt formula."

Another resistant starch, ActiStar(TM), is based on tapioca starch, which is known to work well in critically sensitive product applications concerning flavor and taste, notes Dorothy Peterson, sales specialist, starch ingredients, Cargill Food & Pharma Specialties, Minneapolis. "Because of its very fine crystalline structure, this ingredient provides a pleasant mouthfeel in cultured-dairy-based products," she says. "It is stable at low pH and during food fermentation and can tolerate temperatures up to 120?C."

Specific types of products often dictate specific stabilizing ingredients. "For acidified-milk or -whey beverages, pectin -- and in particular, high methoxy pectin -- is an ideal stabilizer," notes Florian Ward, Ph.D., senior principal scientist, TIC Gums, Belcamp, MD. "A combination of guar and pectin works well for acidified-milk beverages. Pectin has the effect of a clean label and prebiotic effect. Lambda carrageenan also works well in acidified whey or milk because of its negative ionic charge. A low level of carrageenan is ideal in this application." In smoothies, xanthan gum is a good prebiotic choice. It is very acid-resistant and heat-stable.

Other healthy drinks
For clear beverages, the short-chain inulin ingredients work well and will add minimal viscosity when used at lower levels. In other nutritional beverages, inulin can reduce calories while contributing a pleasant caramelized flavor and allowing the formulator to decrease the sugar levels. Inulin is labeled as a fiber, rather than a sugar. Unlike many other fiber sources, inulin has good solubility. "In high acid beverages, there is some potential for hydrolysis, especially if the product is not refrigerated," says Martin. "A combination of refrigeration and high solids will minimize hydrolysis." Inulin also works synergistically with high-intensity sweeteners.

Inulin has excellent heat stability. It waltzes through sterilization and pasteurization unscathed. However, pH can be an issue, especially in extended-shelf-life high-acid beverages. For example, carbonated beverages, which typically have a pH of 2.8 to 3.2, are probably not a good system for inulin. "When formulating extended-shelf-life beverages in the pH range of 3.5 and 4.0, food formulators might have to work to optimize a stabilizer system," comments Kaper. "At this pH, food developers can check with the suppliers for time and temperature models to minimize any stability issue." Handling issues become obsolete above 4.0 pH.

"The use level of FOS varies depending on the application," notes Douglas. "The recommended dose for the benefits ranges from 1 gram to 3 grams per day, which can be divided into four daily servings of the finished product. For beverages, where the typical serving size is 8 fl. oz., the use level would be 0.31%, based on a 0.75-gram dose of FOS per serving."

"In beverages, polydextrose has the advantage of being very water soluble and having a clean taste and neutral to mildly sweet flavor," comments Brooks. "It is 80% soluble, making it easy to add to both dairy and clear beverages." Expect to find more probiotics and prebiotics in other food systems, including bakery and confections.

Sweet treats
Bakery applications can serve as healthy environments for probiotics. For example, Kopp suggests a cream sauce, such as the filling inside of a snack cake. This system has low water, low humidity and low heat because the high-solids cream filling is injected after baking the cake. He also noted oils as another probiotic-friendly bakery environment. Developers can spread or spray oils on top of baked goods, or use them internally in various bakery products.

Recent research in Europe is exploring the health benefits of dead probiotics. This research shows that humans can also derive benefit from dead probiotic bacteria, which act as a prebiotic in that they help the probiotics to grow. Bakers in Europe have explored fermenting artisan bread with bifidobacteria. This product is appealing to European consumers who place a high value on probiotics and food ingredients.

It is difficult for a probiotic to survive in some bakery applications, but baked products are ideal vehicles for fortification with prebiotics. "From a functional standpoint, short-chain units behave much like sugar, and are approximately one-third as sweet as sugar," notes Martin. "These ingredients contribute to browning and help provide a crisp texture in the finished product, much like sugar. The very-long-chain units behave more like a fat replacer. They provide a creamy texture and can help to lower the fat content in food products. Medium-chain fructans have a blend of properties of both types; they are frequently used for fiber fortification or to reduce flour in low-carb formulas."

With the emphasis on low-carb products, medium-chain fructans are ideal to replace flour. They also have an added advantage in that they will have a softening effect in high-protein nutrition bars. This is because sugar will crystallize, but inulin won't. Inulin is an amorphous solid that helps to extend shelf life. Inulin is also a sweet ingredient from a production standpoint. It can be dry-blended into dry products, as there is no need for hydration. Inulin syrup enhances fruit flavors and increases humectancy in bars, confections and sweet baked goods.

"Resistant starch can be used in place of flour in numerous bakery applications," notes Witwer. "It has been used up to 40% in low-carb bakery products to replace 70% of the flour." Product designers could also add it to granola, which could then be added to yogurt, possibly as a bundled retail product. Formulators could also use resistant starch in a cookie or biscuit shaped like a spoon, which the consumer could use to eat the yogurt.

"As a solid, FOS can be used to reduce the water activity for a food application," adds Douglas. "NutraFlora also improves moisture retention of food products, specially baked goods, where texture is a crucial attribute of the product." Polydextrose works well in baked goods. Food formulators can modify the texture of bars by adjusting the percentage of polydextrose in combination with the moisture content to achieve a texture from crispy to chewy.

Guar gum can be used in baked goods up to 0.35%, and in breakfast foods up to 1.2%, notes Ward.

Another lovely environment for probiotics is chocolate, which designers can use as a topping after baking, injected into a cupcake or drizzled on a croissant after baking.

Confectionery offers a lot of applications for prebiotics as well. Formulators can include up to 4% gum acacia in confections and frosting and up to 85% in soft candy.

"Polydextrose also can be used in confectionery applications, and it is a great choice for calorie and sugar reduction in hard and chewy candy," says Brooks. "It has high water solubility and high viscosity. In sugar-free confections, it allows for sugar reduction without the laxative effects of some sugar alcohols." Product designers can also use polydextrose in fruit spreads and fillings.

Magic from a bottle
Expect more work on the interactions of probiotics and prebiotics in the future. One exciting area is the development of prebiotics that display selectivity toward specific probiotic strains. The industry might also anticipate functional synbiotics targeted toward specific population groups. For example, the gut flora of breast-fed infants is much different that that of formula-fed infants. Supplemental foods for formula-fed infants might be one area for future explorations.

Another targeted area might be the elderly. Around 55 to 60 years of age, the bifidobacterial counts of the elderly markedly decrease, leading to greater susceptibility of various pathogens. Specific synbiotic foods for the elderly might show promise in reducing the risk of gastrointestinal infections.

Also expect more research into how probiotics and prebiotics can affect a wider range of health benefits, including bone health, weight management and reducing the risk of cardiovascular diseases and cancer. That's a pretty tall order for products that might come in a little bottle.

Sharon Gerdes writes and consults for various food industry clients, with emphasis in dairy products, baked goods and nutrition specialty items. She also serves as technical support consultant for Dairy Management Inc.(TM) Gerdes holds a B.S. in Food Science and Nutrition from Kansas State University. She has authored two other pieces on probiotics, which are part of the Danone Vitapole Nutrition and Health Collection.

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