We scrub down our kitchens and bathrooms with antimicrobial cleansers, make sure to cook our hamburgers thoroughlyand swallow antibiotics to treat strep throat infections.

In our ongoing war against bacteria, however, it is easy to forget that many species of these single-celled organisms actually are innocuous — and some are even beneficial. In fact, billions and billions of bacteria call the human body home, and many of these perform duties essential to our physical well-being.

Moreover, when administered in adequate amounts, certain bacteria can promote gastrointestinal health and help prevent common infections. These bacteria, called probiotics, long have been part of the yogurt scene and now are making their way into other dairy products.

By definition, probiotics are living microorganisms that bestow some sort of health benefit on the host — for the purposes of this article, the human body — when they are administered in adequate quantities. In the United States, Lactobacillus acidophilus is the probiotic that shows up most often in dairy products. Other probiotics commonly used in the dairy arena include Bifidobacterium strains and other Lactobacillus strains such as L. casei and L. reuteri.

Both Lactobacillus and Bifidobacterium species are normal inhabitants of the human intestine. But antibiotic use, disease, aging and other factors can negatively alter the microbial landscape, paving the way for a number of health problems. Dairy products containing these probiotic good guys, therefore, can help restore — and maintain — the microflora balance.

Although each strain has its own specific benefits, all the aforementioned probiotics have been found to improve intestinal balance when consumed regularly and adequately.

"Probiotic bacteria exert competitive antagonism to suppress the growth of disease-producing bacteria," says Terri Rexroat, business line manager for Degussa Food Ingredients US LLC's BioActives business line, Waukesha, Wis. "This action can help prevent such maladies as viral and bacterial diarrhea and inflammatory bowel disease, and it can help reduce the effects of lactose intolerance and constipation."

Some strains produce organic acids and/or natural antibiotics that help prevent pathogen colonization, says Rexroat. They also can stimulate the immune system and aid in reducing serum cholesterol levels.

Although L. acidophilus is most widely documented for its impact on lactose intolerance, it has the least supporting documentation of the major probiotics for other beneficial effects, says Anders Henriksson, Ph.D., research manager for probiotics with DSM Food Specialties, Sydney, Australia. The ability of B. lactis to reduce the duration and severity of the rotavirus infection in children has been well documented, he says. L. paracasei also has been shown to have a positive effect on rotavirus infections, as well as on antibiotic-associated diarrhea.

As the evidence of probiotics-related benefits mounts, manufacturers outside the dairy category are showing a growing interest in the bacteria. Numerous supplement manufacturers, in fact, now offer probiotics-packed products in convenient capsule or tablet forms.

Consumers are likely to reap more health benefits, however, by ingesting the bacteria in yogurt, milk or even cheese.

Because it is a fermented product, yogurt makes a natural delivery vehicle for probiotics, says Rexroat. "The probiotics actually participate to an extent in the fermentation and contribute to a pleasing mild flavor profile that is popular in modern yogurt," she says. "The relatively simple production process for yogurt is not too detrimental to probiotics, and when these cultures are handled with care by minimizing vigorous agitation and air incorporation, higher counts can be realized."

Although yogurt's relatively low pH can negatively impact probiotic viability, says Rexroat, the problem can be mitigated somewhat if processors maintain a product pH above 4.1. Other cultured dairy products such as sour cream also provide good probiotic delivery vehicles for many of the same reasons, she says.

In contrast, supplements face obstacles that threaten probiotic viability, including (improperly performed) dehydration and room-temperature storage conditions, says Trish Dawson, senior technical affairs manager for DSM Food Specialties, Menomonee, Wis. In addition, their long shelf life eventually might translate into a reduced number of viable cells.

"None of these conditions occurs in certain dairy products such as yogurt and fermented milk," says Dawson. "The products have a high moisture content, refrigerated storage and a relatively short shelf life. High-moisture fermented dairy products also provide conditions and the opportunity for the probiotic cultures to grow."

Supplements do promise more in the way of live bacteria, notes Mary Ellen Sanders, Ph.D. She runs the Dairy and Food Culture Technologies consulting firm in Centennial, Colo., and also acts as a probiotics consultant to the California Dairy Research Foundation.

"If you take what supplements say on their labels at face value," Sanders says, "they are much higher-potency delivery vehicles for probiotics. I just don't think most people are formulating their yogurts so that people are getting 5 billion or 10 billion (live bacteria) per day."

Of course, Sanders admits she could be wrong. But the failure on the part of U.S. yogurt manufacturers to disclose the levels of live bacteria contained within their products does pose a predicament for consumers seeking certain probiotics-related benefits. Still, she believes food products — dairy products in particular — are far superior to supplements as probiotics delivery vehicles.

"When you eat yogurt, you're not just getting live bacteria, you're getting something that's going to help neutralize stomach acid when you're consuming the bacteria," says Sanders, "and potentially help it survive and get into the intestine alive. You're getting vitamins and minerals that are going to help enhance your nutritional value. You're getting calcium, which has been shown by some research to improve the ability of your intestinal tract to resist certain types of pathogens. … You're getting a range of physiological benefits by eating this complex, very nutritious food product that probiotics can supplement."

One dairy product that does contain substantial levels of beneficial probiotic bacteria is the DanActive® cultured dairy drink offered by the Dannon Co. Inc., Tarrytown, N.Y. The dairy supplement drink, originally sold under the Actimel® moniker, promises "10 times more beneficial cultures than yogurt."

Dairy processors can choose from a number of probiotics products when formulating their products — all designed to perform specific functions.

DSM Food Specialties offers the LAFTI® line of probiotic cultures, which Dawson says are isolated from a variety of sources, but are subjected to a "meticulous screening regime" for strains indicating probiotic effects.

"In vivo and in vitro evaluations of the selected strains have shown clear probiotic effects," says Dawson. "These include benefits such as protection against Listeria and Salmonella infection and reduction in the incidence of tumor formation. More recently, completed human trials have shown a decrease in the symptoms of IBS (irritable bowel syndrome) in patients treated with the LAFTI strains. The trials also demonstrated a significant improvement in the participants' general feeling of good health when compared to the placebo and strains other than LAFTI L10."

All LAFTI strains, adds Dawson, are evaluated to ensure they will remain in high concentrations in the carrier product and can be delivered to the gastrointestinal tract in sufficient numbers to bring about a probiotic effect.

Degussa Food Ingredients has a full line of probiotic cultures for use in dairy and other food products, says Rexroat. The company carries separate probiotic strains such as L. acidophilus, B. lactis, L. casei and L. paracasei, as well as probiotic blends and combinations included in the same package with complete yogurt cultures. It also offers the Designer Direct™ Culture program, which provides customers with custom development and blending services.

Chr. Hansen offers L. acidophilus, bifidobacteria and L. casei "as single strains or as blends," says David McCoy, Ph.D., a principal scientist with the company in Milwaukee. The products are available in both frozen pellet and freeze-dried versions.

"These can be used in fermented dairy products, non-fermented products (such as) acidophilus milk or creatively in any number of products," says McCoy. "We also offer yogurt cultures with the prebiotics as part of the culture for convenience."

The Lactobacillus and the Bifidobacterium strains are very safe, stresses Sanders. Although other probiotic strains are available and used in the supplement arena, she says, dairy processors would probably be wise to avoid most of them — at least until their safety records are proven.

For example, people with compromised immune systems probably should avoid Enterococcus bacteria, some species of which are associated with nosocomial, or hospital-acquired, infections, says Sanders. "They're normal inhabitants of our gastrointestinal tracts; they're used as starter cultures in different cheeses in Egypt; and there are a lot of Enterococcus (bacteria) that enter our system," she says. "But if you're in a certain situation, I would hesitate (to ingest them)."

With all the apparent benefits associated with probiotics, and with dairy products seemingly representing the "ideal" delivery vehicles, one would think U.S. consumers would be actively seeking out these probiotics-infused products and begging for more. But that's simply not the case.

"The U.S. consumer is still very unfamiliar with probiotics and prebiotics," stresses Jim Kappas, director of international and emerging products for Minneapolis-based Cargill Health and Food Technologies (Cargill HFT). "I think consumer education is needed."

Sanders agrees. "I think the overall dominant message to consumers is that bacteria are something to be avoided," she says. "There's a big information gap between the reasonable communication about the downside to bacteria and the positive connotations of the bacteria that can be good for us."

People do, however, seem to "have some sense" that yogurt contains live cultures, Sanders adds, and that live cultures are beneficial.

At gatherings with family and friends, notes Rexroat, she has seen "ed­u­­­cated, intelligent people" demonstrate a "complete lack of knowledge" about food and health benefits. These same people, she adds, are willing to believe information from "sensationalist, extremist sources" and are often not able to sort the facts from the fiction.

"This suggests that the legitimate dairy industry is not getting the message out as well as the general food industry and definitely not as well as the fringe groups," says Rexroat. "It is not safe to assume that consumers know that yogurt is made with cultures that have healthy benefits because many just do not know this. It is imperative that the dairy industry work overtime to correct this message and take ownership of our claims."

McCoy believes consumers afflicted with Crohn's disease and other inflammatory bowel diseases do have a much greater awareness of probiotics' potential benefits than does the general population. "Dairies have tried and are continuing to distribute the message," he says. "They are hampered by being limited in the type of claims they are able to make."

Just as plants grow greener and taller when treated with fertilizer, probiotics grow better when given their own version of "fertilizer" – substances called prebiotics. Prebiotics, usually non-digestible fibrous food ingredients, selectively stimulate probiotic growth within the colon (see sidebar highlighting a research project that used a non-fiber prebiotic — acid whey left over from cottage cheese production).

Commonly used prebiotics include short-chain fructooligosaccharides (FOS), oligofructose and inulin. Oligofructose is a mixed FOS that is produced through the enzymatic hydrolysis of inulin. Inulin is a predominantly long-chain dietary fiber extracted from chicory root.

"Inulin and oligofructose are the most widely offered prebiotics in the dairy sector and can be used for either the nutritional advantages or their technological benefits," says Joseph O'Neill, national sales manager for Orafti Active Food Ingredients, Malvern, Pa. Both substances are all-natural fibers, he says, and processors can use them to support a "good source of fiber" nutritional content claim.

Inulin stimulates the growth of bifidobacteria in the large intestine, says O'Neill. "Many of the beneficial effects of inulin are a result of the short-chain fatty acids produced during the fermentation," he says. "It is believed that the short-chain fatty acids — lactic, propionic and butyric acids— lower the pH in the colon, making the calcium salts dissociate and (become) more bioavailable. It is also believed that the short-chain fatty acids may have an effect on the calcium-transport mechanism, leading to increased mineral absorption."

Orafti's Raftilose® Synergy 1, an enriched form of inulin, "has been clinically proven to boost both calcium and magnesium absorption," says O'Neill. The product also reduces heart health-threatening triglycerides and has demonstrated immune-enhancing effects. As a "bonus," inulin masks the off-notes associated with high-intensity sweeteners, he adds, "leading to a flavor profile more like sugar."

In addition, says O'Neill, products such as Raftiline® inulin can help dairy and other food processors meet the demand for low-carbohydrate and reduced-calorie product offerings. "Raftiline inulin can partially replace the sugar and starch in such formulations and help reduce the digestible carbs they contain," he says. "The natural fibers inulin and oligofructose behave just like sugar, and in combination with high-intensity sweeteners, they have a sweetness profile like sugar."

Cargill HFT offers the Oliggo-Fiber™ family of inulin and oligofructose soluble fibers. Although all of the line's offerings work well in dairy applications, says Kappas, the various grades will differ in their impacts on final product texture or viscosity. In addition, the grades vary a bit in their residual sugar levels. The company has put together a grid to help manufacturers see what product grade works best for a particular application.

An increasing number of manufactures are combining probiotics and prebiotics in their products. Such combinations often are referred to as "synbiotics."

For example, Horizon Organic includes in its yogurts the NutraFlora® brand of FOS, which acts as a food source for probiotics and enhances calcium absorption. Stonyfield Farm puts a "specially enriched" form of inulin into its yogurts. In addition to its prebiotic benefits, says the company, the product has been shown to increase both calcium absorption and bone mineral density.

Although industry and academia have made significant progress in pro­biotics-related research, they admit they still have much to learn.

"First, we have to understand the mechanisms involved," says Sanders. "We need to understand how they work because we want to get away from this 'black box' — just throwing 10 billion in and seeing an effect."

Researchers also need to understand the role of dose and strength and strain, Sanders continues. Most studies have involved fairly high doses of probiotics, she says, so experts really do not have a "good sense" of the levels at which the probiotics will not work. Larger clinical studies that involve greater numbers of people will be needed.

During the next decade, researchers also will focus on attaining a better understanding of individual responses to probiotics, predicts Sanders. "Each person has a very unique flora," she says. "The more we know about an individual's genetic makeup — and the human genome project is going to give us that — and the more we know about their individual microbiological makeup … (the more) we're going to start to be able to categorize people and say: 'We would expect Lactobacillus to work with a person in this particular case.'"

That means consumers soon might be clamoring for customized yogurts and made-to-order milks — as long as dairy processors and probiotics suppliers can successfully convey the probiotics story.

Researchers at South Dakota State University, using funding from Rosemont, Ill.-based Dairy Management Inc. (DMI), recently manufactured a tasty but unusual synbiotic yogurt. What made the yogurt so unique is that it used acid whey left over from cottage cheese production as a powerful prebiotic.

Rajiv Dave, associate professor of dairy science at the university, replaced a portion of the nonfat dry milk in the probiotic yogurt with acid whey protein (AWP). Rich in peptides and amino acids, the AWP contains predigested nitrogen to improve the growth and viability of the probiotic bacteria. The substance also is a good source of calcium.

A consumer taste panel gave high marks to a strawberry yogurt sample containing 1.9 percent AWP.

Although other researchers have attempted to use acid whey in yogurt formulations, says Dave, their efforts failed because the product was added to the milk before heat treatment, and the milk curdled upon heating. To fix the problem, Dave developed a technology for cold blending, or cold mixing, the two ingredients — the yogurt mix with milk solids and the acid whey solids.

"You separately heat treat them so they don't curdle," says Dave. "You mix them when they're cold; then you add the culture and incubate and make yogurt."

It's a win-win situation. Cottage cheese processors get a way to mitigate the huge expense associated with acid whey disposal, says Dave, while dairy processors — and consumers — end up with a more nutritious yet full-flavored yogurt that delivers the proper appearance, body and texture.

To learn more about DMI's research on AWP in fermented dairy products, call its technical support hot line at (800) 248-8829.