Food Product Design: Applications - March 2004 - Cultured Dairy Products

March 2004

Cultured Dairy Products

By Cindy HazenContributing Editor

Perhaps no other saying could describe the cultured dairy category as aptly as the adage, "everything old is new again." Indeed, fermented and cultured milk products may be older than recorded history. Various legends describe the spontaneous production of yogurt. In one version, a pitcher of milk belonging to a Turkish nomad congealed in the warm sun as he rested on a mountain slope. Another story describes a nomad traveling in the Turkish desert who carried a goatskin bag of milk -- the heat and agitation of his camel's movement thickened and acidified the milk. Yet another tale credits Genghis Khan as accidentally creating the first yogurt. Supposedly, his enemies filled his gourd with milk in hope that as he traveled it would sour and poison him. Quite the opposite occurred. Rather than a dangerous foodstuff, he discovered his gourd filled with a rich, fulfilling custard-like food.

Yogurt is reputedly not only nourishing but also life-extending. Elie Metchnikoff, who won the Nobel Prize in Physiology and Medicine in 1908 for his work on phagocytosis, wrote in his book "The Prolongation of Life: Optimistic Studies" of his belief that cultured foods led to longer lifespans. He observed that Bulgarians, who as a culture regularly consume yogurt,   commonly live to 90 or 100 years old. He found similar longevity in certain Russian villages where residents made kefir, a cultured milk drink, a regular part of their diet.

Metchnikoff based his theory on the concept that health -- and hence, longevity -- is linked to intestinal integrity. A normal, healthy intestinal tract contains colonies of disease-fighting bacteria. Cultured dairy products, which contain live bacteria, enhance this normal flora. Additionally, these products are nutritional powerhouses, high in protein, calcium and other nutrients.

A healthy market This good-for-you persona is helping drive the cultured-dairy category. According to Dr. Rajiv Dave, associate professor of dairy science, South Dakota State University, Brookings,   sales of yogurt and cultured milk topped $2.5 billion for the 52-week period ending Nov. 1, 2003. For the category, he notes an increase of 3.1% from the previous year. Yogurt production, excluding frozen yogurt, increased 34.5% over the past 5 years. Drinkable yogurt, a relatively new product, has increased 1,406% since 1999.

Yogurt is clearly the star performer of dairy sales but sour cream sales have also risen. In 2002, sales of sour cream and dips, as reported by the USDA Economic Research Service, increased by 4%. It's likely that the growth of the Hispanic population and the popularity of Hispanic cuisine   among the general public is helping drive sales.

On the other end of the scale, sales of cultured buttermilk and cottage cheese have declined slightly. Though they too are healthy food choices, they've experienced less growth -- in part because they've been overlooked by younger generations.

It's alive The cultured dairy-making process is similar across a spectrum of products. Essentially, dry ingredients such as sugar, stabilizers, nonfat milk solids and/or optional dairy ingredients are mixed with the milk, which is then homogenized and pasteurized. Most manufacturers use high-temperature short-time (HTST) pasteurization. Although actual temperatures and times vary from plant to plant, they usually exceed the minimum requirements of 161?F for 15 seconds for standard milk products. When the milk cools to a certain temperature, manufacturers inoculate it with a lactic acid bacterium, which is available in freeze-dried or frozen pellet form. During the fermentation process, manufacturers maintain yogurt temperature and monitor acid production. When the proper pH is obtained, for example 4.4 to 4.7 for yogurt production, the product is cooled further to stop fermentation.

The microorganisms added vary depending on the product being made. Sour cream, buttermilk and cottage cheese curd use Lactococcus lactis. Leuconostoc species bacteria are also added to cottage cheese. The standard of identity for yogurt specifies that it must be made from Lactobacillus bulgaricus and Streptococcus thermophilus. Subspecies of these bacteria and the strains of subspecies can vary. For example, in sour cream and buttermilk production, Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis or Lactococcus lactis subsp. lactis biovar diacetylactis may be used.

A number of factors come into play when determining the appropriate cultures. According to Marilyn Stieve, senior product manager, cultures for fermented milks, Chr. Hansen, Inc., Milwaukee, WI,   flavor and viscosity should be considered, and acidification would be another important criteria.

Simply put, S. thermophilus contributes body whereas L. bulgaricus is the primary flavor source. Nothing, however, is clear-cut. Not only do the ratios of these two microbes contribute to the final flavor and texture, but the presence of other ingredients in the formulation will determine how these components react. Gary Pieper, technical service representative, Grade A dairy products, Chr. Hansen, says, "Cultures will inherently have changes in their characteristics depending on the ingredient profile that it is being exposed to. Fructose, for example, will discourage the growth of some cultures where it won't have an effect on others."

According to Terri Rexroat, business line manager, Degussa BioActives, Waukesha, WI, all lactic-acid cultures produce acid, and this acid reduces the pH of the milk and gives it the typical product flavor. "What the cultures do in a product can result in a milder flavor," says Rexroat. "They may not produce as much acid or cause the pH to be as low in the final product. A higher pH is going to translate into a milder flavor." This is particularly evident in yogurt production. Today's yogurt has less bite than yogurt produced a couple of decades ago. "A lot of cultures now result in a higher pH in the finished yogurt so there is a milder flavor and really that's probably what's translated into the giant growth in the yogurt industry," she says.

Additionally, specific strains within a culture can develop specific flavors within the product. Sour cream production routinely uses a flavor-producing culture in addition to the acid-producing culture to develop the diacetyl flavor, which gives sour cream its typical taste.   "Without the flavor-producing strains, you're just going to have something that tastes like lactic acid," says Rexroat. "What the flavor-producing strains do is give sour cream or yogurt or buttermilk a much more rounded flavor."

Flavor aside, certain cultures have been selected to produce polysaccharides to build body in sour cream, buttermilk and yogurt. Polysaccharides can vary greatly, from compounds held tightly to the cell wall to those that are released into the medium. They may consist of one type of sugar monomer, such as those produced by Leuconostoc mesenteroides or they may consist of several types of monomers. L. lactis and L. bulgaricus produce several types. In addition to individual culture selection, the presence of sugars in the formula can encourage the amount of polysaccharide production.

According to Stieve, bacteriophage resistance is another important consideration in culture selection. Bacteriophages, viruses that attack and destroy bacteria, kill the lactic acid bacteria and then multiply rapidly, causing inconsistencies in the finished product or at worst, an unusable product. This can be a challenge for the dairy industry because bacteriophages occur naturally in the plant environment. Some dairy processes are more vulnerable. Cottage cheese, which is produced in open vats, is the most susceptible because of the product's exposure. Buttermilk, which is produced in a contained fluid process, is the least vulnerable to attack. Sanitation is critical, though not always effective in elimination because bacteriophages are heat resistant and can remain dormant for years. However, one trait can help the dairy manufacturer stay ahead. "Each virus is specific to one of the bacteria," says Stieve. Rotating the strains of cultures used reduces the chance of bacteriophage contamination.

"Ideally, to have the most consistency, a company should use only one culture system," says Pieper. "But, because of phage, we are required in the culture industry to produce variations in strain selection that allow a plant to alternate cultures. To control phage, you must look at the plant environment and the exposure of finished product to the environment because phage cannot grow unless they are in the presence of a host cell. If you can eliminate the exposure of the finished product to the environment, you can eliminate the ability for the phage to replicate. Alternating the culture is a way to keep a step ahead of the growth or multiplication of phage. Some products are more forgiving than others and some products have very little ability to allow us to switch cultures in and out without having a noticeable affect on finished product. Rotation of cultures is very plant specific and production environment specific. One operation can run one culture per week and then give it a week's rest. Some operations have to alternate more than one culture per day, depending on how often their tanks and equipment are exposed to the same culture. In a cottage cheese operation, because it's an open vat system, it's common to change culture every day because of the exposure that product has to the environment."

The processing culture While cultured dairy products may share the same blueprint, they exhibit notable differences in fat content, use of other ingredients and processing methods.

Sour cream, except when characterized by nutritive sweeteners or bulking flavoring agents, is required by the Code of Federal Regulations (CFR) to have 18% milkfat and a titratable acidity of no less than 0.50%, calculated as lactic acid.

According to Pieper, most plants pasteurize using a vigorous variation of HTST, typically 185?F for 3 to 6 minutes. "Most people run it with a short-time system with an extended hold time to denature the whey protein as much as possible to get the benefit of the water-binding capacity once the product is made," says Pieper. As the product cools, the milk fat crystallizes, which gives it stability. The denatured whey protein provides a more stable product.

"The main difference between buttermilk and sour cream is strictly the fat. Buttermilk and sour cream are nearly identical in operation," says Pieper. Buttermilk is required to have no less than 3.25% milkfat, not less than 8.25% milk solids, nonfat, and a titratable acidity of not less than 0.50% lactic acid. "In buttermilk, you are relying more on the whey protein denaturization and polysaccharide-producing cultures to provide the body and texture because it is a fluid product," says Pieper.   The goal in a buttermilk operation is to prevent the visible whey separation in the container, whereas in sour cream you want to prevent syneresis. Buttermilk is typically cooled prior to packaging where sour cream is packaged at set temperature. If sour cream is cooled past the temperature at which the butterfat will crystallize, you can break down the structure of the product."

The basic formulation for yogurt is very similar to buttermilk -- culture use is the major difference. Streptococcus thermophilus establishes the upfront acid drive. Lactobacillus bulgaricus provides flavor as well as helps in acid production as the product pH declines. Culture selections, blends and the ratios of cultures used can have a major impact on a product's flavor, body and texture.

The milk source can also alter the flavor and texture profile. Sheep's milk creates a creamier yogurt because of the milk's higher protein and fat content. Product made from goat's milk has a characteristic flavor. In the United States, most industrially made yogurt is produced from cow's milk.

Yogurt has a higher milk solids level than other cultured dairy products. During manufacturing, the serum solids content is standardized to a level of 10.5% to 11.5% by the addition of nonfat dry milk or other optional ingredients. CFR specifies that manufacturers can increase nonfat solids content though the addition of concentrated skim milk, nonfat dry milk, buttermilk, whey, lactalbumins or modified whey, however, they must maintain the ratio of protein to total nonfat solids. Frequently, producers use optional ingredients to reduce cost, though some ingredients also can improve quality. For example, 80% whey protein concentrate can enhance viscosity and texture.

The method and timing of flavoring depends on the type of yogurt. Sundae-style yogurts are made by adding fruit or fruit flavorings to the bottom of the retail package and topping with inoculated base. The individual cups are then incubated. In stirred yogurts, which have a creamy texture, the flavors and fruits are added after fermentation. The blended yogurt is then discharged into cups. Drinkable yogurts are simply stirred yogurts, however the solids content usually doesn't   exceed 11%. Also, drinkable yogurts undergo additional homogenization to reduce viscosity.

Stabilizing solutions Sometimes, more body is required than can be provided by the cultures. This is especially true of reduced-fat products.

Modified food starch and gelatin combinations typically stabilize yogurt, according to Douglas Vargo, senior technical service representative, Danisco USA, New Century, KS. The modified food starch provides filling viscosity and fruit piece suspension at the filler. The gelatin creates a settable texture later on in the cooler. "Depending on how much gelatin you use," says Vargo, "you can either get a Jell-O- like consistency   or a pudding-like consistency by just minimizing the amounts of gelatin. For those people who don't want to use gelatin, there are other substitutes. You'll see a lot of whey protein concentrate, pectin and even some chelated agar used in yogurt."

Sour cream utilizes a starch and gum combination. Locust bean gum or guar gum will give the product viscosity, but have little effect on syneresis. "Carrageenan is probably the number one effective ingredient for holding wheying off," says Vargo. Dips based on sour cream face another problem if they contain southwestern spices, because the amylase in jalapeño and other chile peppers will break down starch. Gelatin is used in those formulations.

Nonfat sour creams require a bit of stabilizer wizardry. The fat in regular sour cream contributes to body and texture, so much so that a stabilizer isn't necessary for the product to set. Once the fat is removed, viscosity is built with nonfat dry milk and stabilizer. "You have to use a lot more stabilizer," says Vargo. "You might use 0.5% stabilizer for regular sour cream, and use a 3% level for a nonfat."

Stabilizers in buttermilk are normally starch based. Locust bean and carrageenan gums react synergistically to build body and to protect against whey-off in the carton. Locust bean gum also has the cleanest flavor release.

Probiotics, prebiotics and symbiotics Probiotic bacteria, Lactobacillus acidophilus and Bifidobacterium , are naturally found in the intestinal tract. "The hypothesis is that these bacteria are already present in the intestinal tract, so if you keep continually ingesting these bacteria via a media like yogurt, there is a chance of multiplying these bacteria and maintaining a healthy balance," says Dave. Stress and antibiotic use can impact the microfloral balance of the intestine, allowing a preponderance of coliforms and other unwanted organisms.

Consumers are becoming more aware of the health benefits of probiotics. There is an abundance of scientific documentation. Dave sees tremendous opportunities for the marketing and development of probiotic-containing foods, but he believes that labeling regulations are the main hurdle for U.S. manufacturers. Current labeling laws prevent the declaration of probiotic health claims. "There are no health claims, but some claims are being made for structure and function -- 'keeps the immune system healthy' and those kinds of things," says Robert Garfield, senior vice president of regulatory and technical affairs, the National Yogurt Association (NYA), McLean, VA. NYA has petitioned FDA to define the amount of cultures in yogurt. "The current standard says there has to be certain types of cultures in order for (a) product to be called yogurt, but it does not define how much. We think that's an important number and should be fairly straightforward for consumers," says Garfield.

Prebiotics are oligosaccharides that the intestinal tract cannot digest. "These prebiotics travel to the end of the intestine and survive the process of hydrolysis," says Dave. "These particular substrates go into the right place where there are a lot of the bacteria that need to be balanced. Pathogenic types won't be able to utilize this, but the probiotic bacteria will multiply. Prebiotics are only used by the acidophilus and bifidobacteria. When their numbers come up, they produce acid and keep those bad bugs down."

For example, notes Robert Veghte, business manager, Roxlor International, Wilmington, DE, in yogurt, which contains probiotic bacteria, the inclusion of prebiotics feeds the beneficial intestinal bacteria. "When you put the two together you get what they call a 'symbiotic' because you're adding beneficial bacteria and you're stimulating the growth and a better environment for these beneficial bacteria."

A number of ingredients can act as prebiotics, but product designers often add inulin and fructooligosaccharides (FOS) to dairy formulations. "Inulin is a general term for chains of fructose, linked by beta-2,1-linkages flanked on one chain end by a glucose unit, commercially extracted from chicory root," says John Martin, project leader, Orafti Active Food Ingredients, Malvern, PA.   " Fructooligosaccharides are a specific type of inulin with a degree of polymerization (DP) between two and 10 commercially obtained by synthesis from sugar. Degree of polymerization is the number of monomeric units -- in this case fructose -- in a chain."

Inulin, a soluble fiber, provides a variety of functional and nutritional benefits. According to Martin, it possesses a neutral to slightly sweet flavor and is easy to formulate into a variety of foods. "Inulin has beneficial flavor improvements in food systems, such as reducing the strong acidic flavors in yogurts, as well as the vitamin and/or mineral bitterness in nutraceutical products, beany flavors in soymilk and 'cooling' caused by sugar alcohols in a variety of other commercial products," he says. "When combined with artificial sweeteners, inulin can also round out the sweetness profile."  

From a health perspective, inulin increases calcium absorption, promotes good digestive health, boosts immunity and reduces blood triglyceride levels, while serving as natural source of dietary fiber. "One of Orafti's products, Raftilose® Synergy 1, has been clinically shown to increase calcium absorption by 18% at only 2 grams per serving," says Martin. "Normal usage levels range from 3 to 8 grams of inulin per serving, but inulin has been utilized in quantities in excess of 15 grams per serving with no flavor or digestive effects."

Roxlor offers two lines of ingredients with prebiotic benefits. The inulin-base prebiotic line enhances the flavor of sugar alcohols such as maltitol, mannitol and sorbitol. The oligofructose-based product line acts as a sugar-replacement system that provides sweetness in 1:1 or 10:1 ratios to sugar. "You would simply add them in place of added sugar and it would provide you with a prebiotic-fiber source as well as the sweetening you would need," says Veghte.

GTC Nutrition, Golden, CO, offers two concentrated short-chain fructooligosaccharide (scFOS(TM)) products that can provide specific structure/function claims because they increase mineral absorption. The use of scFOS contributes to lower pH in the colon, which keeps minerals in a more absorbable form. A second mechanism that may contribute to enhanced mineral absorption is the increased expression of a calcium-binding protein in the colon when scFOS nourishes probiotic microflora. These factors work together to extend the opportunity for calcium absorption beyond the small intestine and contribute to the higher level of mineral absorption associated with the use of scFOS.

Linda Douglas, Ph.D., R.D., manager of scientific affairs, GTC Nutrition, describes one product this way: "It is a prebiotic soluble fiber that very nicely adds an unobtrusive, mildly sweet fiber to any type of cultured dairy product. It is perfect for providing fiber and mineral absorption in one easy step." Manufacturers who use this product can place a structure/function claim on their label that this product enhances calcium absorption. GTC carries this concept further with a prebiotic calcium blend. "This takes the calcium absorption power of the short-chain FOS product and blends it with a unique mineral matrix," says Douglas.   "It's available in a form that's appropriate for cultured dairy products. We would like to see this product in a calcium-enhanced or extra-calcium type of cultured product." That product could then be promoted as "maximum calcium absorption."

Sweet trends "There are a lot of opportunities for cultured milk products," says Dave. "The trend is saying that it's going to go up further in the United States. Everybody understands that yogurt has all the positives -- especially with the trend in probiotics added in it, everything is healthy, tasty and refreshing." Besides healthfulness, these products offer convenience and kid-appeal.

Walt Postelwait, industry director for sweet and savory, Degussa Flavors & Fruit Systems, Cincinnati, OH, finds that the popularity of yogurt flavors is changing. "A couple years back, dessert-type profiles were popular," says Postelwait. " I think we're seeing a swing back to some more-exotic fruit blends, taking your mainstays like strawberries, vanillas, etc. and blending them with some new exotic type of fruits, like kiwis, mangoes, papayas."

Fruit and fruit preps can be blended in swirls and colored vibrantly to make them more appealing to children and even to some adults. Sprinkles, much like those found on ice cream sundaes, add to the fun. To make these products even more enticing, packaging is key -- be it with brilliant graphics or unusually shaped containers.

Perhaps nothing speaks more of the creativeness of cultured dairy manufacturers in product generation than the development of tube yogurt. No doubt, Metchnikoff couldn't have imagined yogurt eaten straight from a prepackaged cylindrical container. Truly, everything that is old can be new again.

Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached at [email protected] .

Back to top

3400 Dundee Rd. Suite #360Northbrook, IL 60062Phone: 847/559-0385Fax: 847/559-0389E-mail: [email protected]Website: www.foodproductdesign.com