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Yogurt: Enhancing a Superfood


Photo: Chr. Hansen, Inc.

In the past decade, doctors, nutritionists and health magazines have published various lists of “superfoods” that might include some 10 to 24 different foods touted to enhance health, defy aging and impede the progression of changes that lead to diabetes, hypertension, Alzheimer’s and cancer. The foods are usually listed in alphabetical order, so yogurt is usually the last—but definitely not the least—of these superfoods.

Yogurt starts with a healthy base of dairy protein and calcium. Add billions of friendly bacteria, a pleasant taste and creamy texture, and a superfood is born. But yogurt is also the perfect delivery vehicle for added vitamins, fiber, essential fatty acids and antioxidants. A growing trend among yogurt manufacturers is to include a trademarked strain of probiotic bacteria, and possibly other selected ingredients such as fiber, to create a product that delivers a specified health benefit, or is targeted to a specific population group.

Making a good thing better 

For centuries, people in some parts of the world have consumed yogurt and fermented milk. It came naturally that these types of products were carriers for probiotics. “This is partially due to the fact that some of the probiotics, like Lactobacilus acidophilus, L. casei or Bifidobacterium, can grow in milk,” notes Mirjana Curic-Bawden, Ph.D., senior scientist, Chr. Hansen, Inc., Milwaukee. It’s also important that the chosen food system is considered healthy and can deliver a live cell count that is high enough to provide a beneficial effect. Levels of 109-11 cfu are typically used in clinical trials.

Yogurt’s base, milk, has long been recognized as a good source of calcium, but the benefits don’t stop there. “An accumulation of research over the past 30 to 40 years has shown that milk and milk products play a role in reducing the risk of chronic disorders, including osteoporosis, hypertension, excess body weight and body fat, and colorectal cancer,” notes Pete Huth, directory of regulatory and nutrition transfer, Dairy Management, Inc.™, Rosemont, IL.

A targeted approach 

Some manufacturers get very specific in targeting yogurt with probiotics to specific health benefits, such as weight control or regularity. “In my opinion, this trend will continue. However, the specificity of claims will be quite limited by what the consumer wants to hear and what FDA will allow to be stated,” notes Mary Ellen Sanders, Dairy and Food Culture Technologies, Centennial, CO. “Claims on immunity, regularity, intestinal health, oral health, vaginal health, staying healthy are all possible. Certainly there are human studies in the body of published work on probiotics which could support these statements.”

A probiotic effect is strain specific. Not every L. acidophilus or Bifidobacterium strain will have a probiotic effect. “The effect has to be documented in clinical trials,” adds Curic-Bawden. “Documented probiotics strains always have the specific ID (unique strain designation composed of letters and/or numbers).” Companies might also give a strain a trademark name, in addition to the scientific name, such as Bifidus Regularis™, the trademark name for Bifidobacterium animalis.

Some products use a single strain, while others combine several strains of probiotic bacteria. Curic-Bawden notes: “The most recent trend in Europe and Asia is to use one strain. But that strain is, as a rule, supported by extensive scientific and clinical documentation. These products have cell counts that are documented to confer health benefits, and most of them have structure/ function (or biological function) claims.” The product’s cell count at the end of shelf life must be as high as that used in the clinical trials. Targeted health benefits include:

Weight management. Who hasn’t noticed Yoplait’s yellow polka-dot bikini ad highlighting the benefit of yogurt as part of a reduced calorie diet? Recently, Dannon introduced Crave Control™ yogurt with Protein- FiberPlus™. The company’s website notes: “Studies have shown that consuming foods rich in protein and fiber help reduce hunger sensations.”

Digestive health. Perhaps one of the most substantiated health benefits of probiotics is their ability to decrease the incidence or duration of certain diarrheal illnesses. Clinical studies demonstrated the efficacy of one yogurt in reducing transit time in elderly subjects. One probiotic strain has been clinically proven to restore high levels of beneficial bacteria to pre-antibiotic levels faster than the body does on its own. Various prebiotics provide a source of fiber, and promote the growth of beneficial bifidobacteria.

Better bones. Yogurt is an excellent source of calcium, and clinical trials show that specific prebiotics boost calcium absorption. Most yogurt also contains vitamin D, and FDA recently proposed revising the calcium and osteoporosis health claim to include vitamin D.

Cardiovascular health. Human studies have shown blood-pressure reductions with fermented milks, and adding specific whey proteins or a unique patented grape seed extract might offer further reductions. Plant sterols in yogurt can reduce low-density lipoprotein (LDL) cholesterol and create a heart-health claim.

Allergies, immunity and kids’ health. Many yogurts are targeted to the younger generation, some including EPA and DHA omega-3 fatty acids. Children’s health has been an active area of probiotic research. “Studies conducted in day care settings on levels of diarrhea, respiratory illness, absences, dental caries, etc. are very targeted toward kids,” says Sanders.

Natural and organic. Besides taking sugar and fat out of certain products, yogurt manufacturers are also taking out artificial flavors, colors and preservatives.

Survival and delivery tactics 

Yogurt naturally delivers healthy doses of calcium and protein, and can also be easily fortified with a range of vitamins, antioxidants, probiotics and other beneficial nutrients.

By far the most important addition to yogurt is probiotic bacteria. A 2001 FAO/WHO report defines probiotics as “Live microorganisms which when administered in adequate amounts confer a health benefit on the host.”

“Yogurt has a shelf life of 42 to 60 days and has to be refrigerated,” says Curic-Bawden. “It is more likely that yogurt (or milk) will have adequate amounts of probiotics, as compared to supplements that may have been kept and handled under uncertain conditions. Also, the proteins and other dietary components present in a food matrix provide certain protection to probiotics during passage through the stomach.”

Most U.S. yogurts contain a cocktail of several “live and active cultures.” Title 21 of the Code of Federal Regulations (CFR), Part 131, Section 200, requires that yogurt contain Streptococcus thermophilus and Lactobacillus bulgaricus. These bacteria may help lactose digestion, and some scientists consider this to be a probiotic effect, while others do not consider these to be true probiotics. “During the production of yogurt, these cultures grow fast and dominate the total number of live and active cultures,” notes Curic-Bawden. “Additional strains that are present (L. acidophilus, Bifidobacterium, L. casei, L. rhamnosus) usually are not scientifically documented and not present at the levels demonstrated to confer health benefits.”

Growth and survival of a probiotic culture in different food products is strain specific. For example, some sugars, especially at high concentrations, can decrease probiotic survival. Neither sucralose nor acesulfame K seem to be of concern. Some probiotic strains are tolerant enough for a range of food products. For instance, the same probiotics can be used in spoonable and drinkable yogurts, and kefir, a traditional fermented milk from Eastern Europe and Russia with multiple strains of lactic acid bacteria and yeasts. Kefir has shown double-digit growth in each of the past five years.

Evidence supporting dairy as a delivery vehicle for probiotics is still emerging, and some variations between individual probiotic strains is likely. Todd Klaenhammer, Ph.D., director, Southeast Center for Dairy Research, Raleigh, NC, says: “Bifidobacteria, which are often delivered in yogurts, preferentially ferment lactose—so delivery in milk-based formats may be advantageous.” A study by Nestlé (Journal of Bacteriology, 2006; 188:1260-1265) observed that, for Bifidobacterium longum, “When growing concomitantly on both sugars, glucose consumption is strongly reduced until the complete depletion of lactose.” Another report, “Functional Dairy Products,” edited by Mattila-Sandholm and Maria Saarela (2003, Woodhead Publishing Ltd.), showed increased survival rate of the probiotic strain, Lactobacillus rhamnosus GG, in milk and cheese vs. a freeze-dried powder.

In any food, it is important to start with targeted probiotic levels and ensure those levels are maintained during the shelf-life of the product. Achieving high cell counts in a fresh fermented product depends on inoculation rate and growth (incubation) conditions. “Keeping a high cell count during 50 to 60 days of shelf life depends on numerous factors, such as pH of the product, presence of dissolved oxygen, addition of various preservatives and storage temperature,” says Curic-Bawden. “Most of the popular functional ingredients that can be added to yogurt, such as plant sterols, vitamins and omega-3s, will have no negative effect on cell count, but manufacturers should test their specific line for viability to be sure.”

Generally, probiotics are not recommended for products that will be pasteurized after fermentation and/or hot filled. “Manufacturers should always inoculate at good levels and work closely with the culture manufacturer for recommendations on how to grow the culture, how to store the product, and even how to package it,” notes Curic-Bawden. “Some probiotic strains have shown sensitivity to oxygen, especially at 50 to 60 days. Some manufacturers may want to add a preservative to prevent yeast and mold growth. Common preservatives such as potassium sorbate have not shown any negative effect on survival,” but they must be added after the fermentation. Additionally, prebiotics can improve survival through the GI tract. Some might also have a positive effect on growth during milk fermentation, but this effect depends on the prebiotic and also varies from one strain to another.

Specialty ingredients 

Yogurt is a good vehicle for many nutritional ingredients, because of its refrigerated storage, flexibility as to where in process a nutrient can be added (before or after set), and its final consistency, which provides uniformity during shelf-life. “Nutritional ingredients in beadlet or powder forms, such as lutein, zeaxanthin, EGCG, probiotics, CoQ10, lycopene, have been tested by DSM in yogurts and found to be stable,” notes Diane-Louise Hnat, senior marketing manager, new business development, DSM Nutritionals, Parsippany, NJ. “As a matter of fact, we have even used yogurt as the delivery vehicle for numerous new ingredients when we conduct a bioavailability study on them prior to their introduction into the marketplace. Omega-3 EPA and DHA are very versatile, in that powder, oil or emulsion forms can be incorporated into yogurt. Thus, the yogurt manufacturer can choose what works best or easiest in his process.

“In many cases, a nutrient will have an addition level as defined in its GRAS dossier, albeit a selfaffirmed GRAS or with FDA notification,” Hnat continues. “As mentioned before, some nutrients have well-recognized claims. Some marketers take more risks than others to make certain claims about a nutrient added to a product. Sometimes the level of a nutrient added to a food product is constrained by its effect on color, its effect on texture or flavor, or its effect on shelf life.”

Protein power 

In addition to its nutritional benefits, protein provides such functional characteristics as reduced syneresis and improved mouthfeel in yogurt applications.

Protein provides functional and nutritional benefits and typically comes in the form of nonfat milk, ultrafiltered nonfat milk, whey protein or soy protein. Whey proteins contribute high-quality protein, and whey protein isolate can boost the immune system and contribute to overall health. “Certain whey proteins, such as Biozate 1, can have a positive impact on cardiovascular health through reduction in blood pressure and cholesterol,” according to Laurie Davis, director of analytical research and application sciences, Davisco Foods International, Inc., Eden Prairie, MN.

Functionally, “they also reduce syneresis and improve mouthfeel and texture,” Davis adds. “This can be either a positive or negative, depending on the system. A manufacturer may choose to eliminate other gelling ingredients when using higher levels of whey protein, as it can add more texture or thickness.” Manufacturers might go as high as 7.5%, but typical usage rates in yogurt will be 2% to 5%. In a drinkable yogurt, manufacturers would add the whey protein isolate to the base yogurt, and then add that to a beverage formulation.

“Yogurt is an easy vehicle to add protein to the diet, and a great way for individuals to consume more protein,” says Davis. “Clarity won’t be a factor when selecting a whey ingredient for a yogurt application, so manufacturers should try to choose a whey protein with the cleanest flavor, especially for plain yogurt, which is a pretty bland system.”

Soy protein products are sources of essential amino acids for human metabolism and contain many of the amino acids needed for growth and development. Soy works for vegan formulations. Soy protein is also rich in dietary isoflavones, phytonutrients that play a role in women’s health. “When added to a yogurt application, soy protein is dairy and lactose free and does not contribute to cholesterol,” says Lisa Bradford, soy foods technologist, ADM, Decatur, IL. “In addition, incorporation of soy protein in a yogurt formula can yield a product that has reduced saturated fat and lower total calories.

“In a yogurt application, soy proteins display dispersion, solubility, emulsification, and contribute to the viscosity and/or texture of the final product,” adds Bradford. “Other functional ingredients include fats and emulsifiers which aid in mouthfeel and smooth texture. Stabilizers enhance texture as well, also playing a role in suspending solids.” Corn sweeteners promote sweetness and enhance the body of the finished product and some, such as dextrose, serve as fermentation media for the starter culture. Fruit juice or preps enhance flavor and can help mask soy’s off-flavors.

Grape seed extract 

A growing number of studies show fermented milks reduce blood pressure. Clinical trials have also shown that a patented grape-seed extract, MegaNatural®BP, can reduce blood pressure. According to Ron Martin, vice president of sales and marketing, Polyphenolics, a division of Constellation Wines U.S., Inc., Madera, CA: “Subjects who were given a dosage of 150 mg and 300 mg once a day for one month showed an average drop of 12 mm drop in systolic and 8 mm drop in diastolic blood pressure. The placebo group had no change in their blood pressure. This grape seed extract functions at the level of the endothelial cells, helping them to work properly by producing nitric oxide, which keeps blood vessels flexible.”

Grape seed extract’s astringent, but not bitter, note makes it suitable for many fruit flavors, including lemon, lime, strawberry, cranberry, pomegranate and mango. In a 12- to 16-oz. yogurt beverage, 150 mg can be added, with moderate astringent notes.

This grape seed extract is GRAS, and allows a structure/ function claim. It “supports normal blood pressure when already in the normal range,” says Martin.

Prebiotic bonus 

Adding color and flavor to the fruit prep, rather than the white mass, can offer a more consistent finished product.

Many yogurts incorporate both probiotics and prebiotics for a “synbiotic” food. Prebiotics include resistant starch, which passes through to the intestine where it functions as a dietary fiber. Polydextrose, a slowly fermented prebiotic, can sustain fermentation all the way to the distal end of the large intestine with less gas and no lactic-acid accumulation. Gums that function well as prebiotics include gum acacia, hydrolyzed guar gum and pectin. Some unabsorbable lactose derivatives, including lactulose and lactitol, serve as prebiotics.

The most researched and best-known prebiotics are inulin and oligofructose. “Inulin is found in over 36,000 plants, including artichokes, leeks and garlic, and is composed of glucose and fructose chains with a degree of polymerization (DP) of 2 to 60 units,” notes Joseph O’Neill, vice president of sales and marketing, Orafti Active Food Ingredients, Malvern, PA. “Oligofructose includes molecules with a DP of less than ten and is produced through partial enzymatic hydrolysis. The unique property of both is that they contain a non digestible beta (2-1) linkage between fructose monomers. These prebiotics are a source of soluble fiber and provide both nutritional and functional benefits in foods. They selectively promote the growth of bifidobacteria and improve digestive health and efficiency.” Various inulin and oligofructose products may have different fiber contents, so rates of 2.6 to 2.9 grams per serving will contribute 2.5 grams and support a “good source of fiber” claim.

Oligofructose is available in powder and as syrup. “In fruit preps, it will also provide sweetness and is often used in combination with high-intensity sweeteners to bring the taste profile closer to a sugar control,” says O’Neill. “Inulin also adds texture to the fruit prep. In the white mass, inulin enhances the creamy texture, rounds out the flavor profile and serves as a fat mimetic. It has the advantage of building body, mouthfeel and creaminess without contributing excess viscosity. In soy yogurts it can mask any beany notes that might be present.”

Flavor tricks 

“Yogurts and yogurt drinks in which health benefits are naturally present have driven flavor trends, such as dark fruits and berries, including pomegranate, açaí and blueberry,” notes Marie Cummings, manager of food applications and product development, David Michael & Co., Philadelphia. “Fortification and the addition of grains to dairy foods have also driven trends.”

Vitamins, proteins, caffeine, omega-3s and other “good for you” ingredients may have notes that require special flavor-masking systems. In fruit-on-the-bottom yogurt, manufacturers can flavor the fruit prep or the white mass. “The fruit prep is delivered in the range of 8% to 20% to the finished product. The prep contains sweeteners, colors, flavors, grains, functional ingredients and stabilizers,” Cummings notes.

“The selection and amount of sweetener systems and stabilizers may affect the flavor of the yogurt. There is an advantage to adding the color or flavor to the fruit prep rather than dosing directly into the yogurt. The color and flavor can be more evenly distributed with minimal variation in the finished product.” 

Sharon Gerdes writes and consults for various food industry clients, with emphasis in dairy products, baked goods and nutrition specialty items. Her career includes experience as both a food and flavor technologist. She holds a bachelor’s degree in Food Science and Nutrition from Kansas State University.

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