No matter the strain, a yogurt will contain live and active cultures only if it undergoes heat treatment before acidification. The criteria of the National Yogurt Association, McLean, VA, for live and active cultures state that a finished yogurt must contain at least 1 billion live lactic acid bacteria per gram at the time of manufacture, and those cultures must remain active for the stated shelf life. Some research suggests that prebiotics—nondigestible fibers that serve as sources of carbohydrates for probiotics in the GI tract—enhance survival of probiotics in fermented milk and yogurt, and also during passage through the GI tract. “Besides ingredients like inulin, fructooligosaccharides and polydextrose,” Curic-Bawden says, “we’ve witnessed the rapid extension of the range of natural ingredients that have potential prebiotics effects.” Again, those effects are unique to each pro- and prebiotic—or synbiotic—pair. To achieve a synbiotic effect, she says, “a specific prebiotic should selectively favor the probiotic strain. The effect has to be tested in vitro and in vivo.”
Friendly fats
In addition to probiotic cultures, other, less-intuitive functionals are finding their way into yogurt. Among the more popular is the omega-3 fatty acid docosahexaenoic acid (DHA), associated with everything from healthy infant neural development to reduced heart disease risk.
As a long-chain polyunsaturate, DHA is prone to oxidation from prolonged exposure to oxygen, high temperatures and transition metals like copper and iron. Yogurt’s refrigerated storage and short shelf life makes it an ideal medium for omega-3 stability.
Experts offer several tips for working with omega-3s: If a yogurt undergoes high-shear mixing, limit its exposure to the atmosphere by shortening mixing times, keeping temperatures low and covering the mixing vessel. Add the DHA as close to the end of production as possible, such as prior to homogenization. Blend the oil with other ingredients to thermally stabilize it and to reduce its surface area. Better yet, work with encapsulated oils, and take advantage of chelating agents like citric acid and EDTA to sequester pro-oxidant metals. Nonfat applications are harder to fortify than their fat-containing cousins, but even so, some manufacturers have packed as much as 32 mg of DHA into a single 6-oz. serving, qualifying the product for an “excellent source” of DHA claim.
Another healthful fat is conjugated linoleic acid (CLA), a natural constituent of ruminant meat and dairy products with demonstrated weight-management benefits that have prompted some manufacturers to add it to yogurt. “Clinical evidence supports the role of CLA in many aspects of reducing body fat, increasing lean muscle and enhancing healthy, active living,” says Patrick Luchsinger, marketing manager, North America, Lipid Nutrition, Channahon, IL. “This means that products can be positioned not only to help dieters, but also those who want to maintain weight and certainly those who wish to enhance their exercise program for optimal body composition. This increases consumer interest in yogurt at a time when health and wellness is paramount.”
His company markets a form of CLA that “is appropriate for use in all types of yogurt,” Luchsinger says. CLA particularly shines in drinkable applications because the proteins in the beverages double as emulsifiers for it. To establish that emulsion, he suggests adding the CLA to yogurt under continuous mixing and at a temperature around 140°F. After homogenization, applying a heat treatment can extend the product shelf life. The ingredient can withstand UHT and standard pasteurization, and can be added before or after fermentation. “In the case of a fermentation step,” he says, “the CLA can be emulsified in the milk, after which a standard process and fermentation can follow.”
CLA is also a polyunsaturated fatty acid liable to oxidation. Avoiding the usual triggers—oxygen, heat, light, transition metals—is standard, but as with DHA, “other factors may help avoid oxidation, like antioxidants and the chelators citric acid and EDTA,” Luchsinger says. As for the levels that yield a health benefit, clinical trials of his company’s product have pointed to 3 grams as effective. “This can be split into different doses or consumed at one time,” he says, “so manufacturers may choose to add 1.5 grams per serving and note that it contains one half the effective daily dose.”
Protein power
Like CLA, whey protein is a natural component of dairy products that manufacturers are adding to yogurt. According to Reed, the reason for doing so is elementary: “Protein, overall, is a huge trend.” But while health-minded consumers want more protein, they don’t want more chalky, protein-powder shakes. “They’re looking for a comfortable medium that’s familiar to them and that delivers nutrition benefit,” he says. Enter yogurt. “It’s portable, it’s convenient, it’s a reasonably sized serving, and it’s really targeting those active, exercise-involved individuals.”