Pumped-Up Dairy

To many, fortifying dairy products means the traditional practice of adding vitamins A and D to milk, which dates back to the 1930s. The driving force for fortification was a concern about vitamin-D deficiency, which eventually would lead to the development of rickets. At that time, milk was considered the best carrier to supply an adequate level of vitamins A and D to the human diet, because people consumed it daily, especially kids.

But today, fortification offers even greater possibilities. Although consumers know more about food and diet than ever before, most exceed their daily requirements for fats, carbohydrates, proteins and calories. Yet many still don’t come close to getting enough vitamins, minerals, complex carbohydrates, essential fatty acids and other micronutrients. Most nutritionists recommend getting daily nutrition from foods, rather than supplements, increasing interest in fortifying foods to meet these daily deficits. Milk and dairy products can be ideal vehicles for fortification.

Throughout history, dairy products have maintained an overall healthful image, even during the recent years’ flux and confusion about all food consumption. Though dairy products like milk, yogurt, cottage cheese, ice cream, dairy-based beverages, process cheese and natural cheese have their own unique nutritional benefits, using dairy products today as a carrier of added essential nutrients still makes good sense.

An 8-oz. serving of milk fortified with vitamins A and D fulfills a portion of our daily requirement for vitamins A (10%), D (25%) and C (4%); calcium (30%); and smaller amounts of vitamins B2, B6, thiamin (B1), niacin, folate (B12), phosphorus, magnesium, potassium and zinc. The majority of dairy products supply a similar dose of vitamins and minerals — except for the A and D levels, since most nonmilk and non-fluid-milk manufacturers do not use vitamin-A- and -D-fortified milk. Given this long list of vitamins and minerals, it’s hard to believe dairy leaves that much room for fortification, but it’s true.

Ingesting the recommended three daily servings of milk, yogurt and cheese that Dairy Management, Inc. (DMI), Rosemont, IL, recommends for strong bones makes it easy for the U.S. population to achieve the daily requirement for calcium. Statistics, however, show that most people are only eating 1.5 servings of dairy per day. Suddenly, the concept of fortifying dairy foods with vitamins and minerals, or even calcium, doesn’t sound so silly. As it turns out, vitamin and mineral suppliers have already thought about fortifying dairy products and have the ingredient technology and the application experience to pass on to dairy processors. Vitamins and minerals have their own specific usage guidelines.

Dairy products, such as drinkable yogurt or other dairy-based beverages, often have 25% of the daily value of vitamins like A, C, E, B6, thiamin, niacin, folic acid, biotin, riboflavin and pantothenic acid. Since dairy products are heat-processed to at least pasteurization temperatures, vitamin heat stability becomes an issue. Processors can minimize vitamin loss by experimenting with encapsulated versions or by adding the vitamins at the optimal stage of processing to protect those that are oxygen- and heat-sensitive.

Other ingredient interactions with vitamins can lead to product defects. Vitamin C can react with certain minerals, causing undesirable color development. Overfortification with vitamins, especially the B vitamins, often creates metallic flavors in a dairy product.

Recent research funded by DMI and conducted by Carl Brotherson, associate director of the Western Dairy Center, Utah State University, Logan, used high-pressure injection technology to inject vitamins D, B6 and folic acid into Cheddar and mozzarella cheeses. After a 330-day ripening period, the vitamins had little or no effect on the ripening process or cheese flavor. Brotherson was concerned that the starter cultures and non-starter cultures might consume the vitamins, but primarily the folic acid showed the highest loss level (40%).

Mineral fortification of dairy products, meanwhile, has a different set of issues. It is not uncommon to find dairy products fortified with up to 30% of the daily value of some minerals. Some minerals commonly added to dairy products include calcium, magnesium, iron, zinc and phosphorus.

Selecting the right form of a mineral for an application is the first hurdle. The high level of calcium in dairy foods makes it important to understand the mineral chemistry of milk before selecting the form for fortification. “Calcium in dairy products exists as amorphous tricalcium phosphate or bound to protein in the form of calcium phosphate,” says Stephan Lihl, Ph.D., business unit manager, Food, Chemische Fabrik Budenheim, Germany. Milk and other dairy products are very sensitive to the presence of minerals, especially soluble minerals. Even small changes in the mineral balance could have a tremendous effect on the milk proteins. Soluble calcium sources could cause protein precipitation, undesirable in all dairy products.

Minerals are available in organic and inorganic forms that are either soluble or insoluble. Each form delivers a different level of mineral content and bioavailability. “Organic mineral sources have a higher bioavailability in comparison to inorganic minerals,” says Saul Koder, vice president of business development, Gadot Biochemical Industries LTD., Haifa Bay, Israel. Tricalcium phosphate and calcium carbonate have the highest levels of calcium (40%) but the lowest solubility. Calcium lactate has one of the lowest levels of calcium (13%) but the highest solubility. Milk minerals derived from whey contain 25% calcium, 40% phosphorus and a variety of other minerals with good solubility.

Combining mineral sources offers formulators a good option. “To maximize efficiency and minimize cost of mineral fortification, a combination of milk minerals spiked with calcium phosphate could produce a mineral blend with a higher level of calcium,” says Lihl. Mineral phosphates are insoluble over a wide pH range, so they remain unable to react with other food components, such as proteins. “Typically you would choose calcium phosphate or calcium citrate over calcium carbonate or gluconate, and magnesium citrate over magnesium lactate or oxide to fortify dairy products,” notes Koder. Some forms of calcium have additional health benefits. “Calcium citrate is less likely to form kidney stones as compared to calcium carbonate or calcium oxalate,” he adds.

The insolubility of mineral phosphates can also be a disadvantage, causing sedimentation in a dairy product. Using micro- and ultra-fine minerals can alleviate this. “Calcium phosphates with a small particle size can provide fortification with a smooth mouthfeel in fresh cheese, yogurt, cottage cheese and process-cheese products,” says Lihl. Drinkable yogurts are a newer application for tricalcium phosphates and magnesium phosphates in the United States. Weight-loss drinks often use premixes containing dicalcium phosphates as a carrier for vitamins and other functional ingredients. “We have determined the best granulation for dairy products to minimize any added mouthfeel effects,” says Koder.

Micro-fine mineral phosphates can be stabilized by the viscosity of the dairy product itself or by the addition of small amounts of hydrocolloids, sequestering agents, and/or a reduction in pH. Because fortifying agents might affect the pH of dairy products and the heat stability of milk proteins, it is often necessary to use disodium phosphates and/or citrates as buffering agents.

The mineral iron once created big problems for dairy products. “Fortification with iron salts is known to promote oxidation in dairy products, resulting in rancid flavors,” says Lihl. Ferric phosphate remains unreactive, making it feasible to fortify dairy products with iron. “Regardless of the recommended levels of added nutrients needed for specific health benefits, a desirable flavor, texture and appearance are the most important attributes to pay attention to when fortifying dairy foods,” he notes.

If adding essential nutrients isn’t enough for a dairy application, adding health-enhancing cultures can provide more value. Commercial yogurt came to the United States in the 1970s, and probiotics tagged along as a necessary ingredient for yogurt manufacture. These are also recognized today for their role in good intestinal health.

With yogurt and yogurt drinks experiencing double-digit growth within the last year, according to the July 2003 issue of Dairy Foods, this category of dairy products is definitely a success story. The magazine noted that drinkable yogurt sales have grown 630% since 1999 and now account for greater than 15% of yogurt sales in the United States. With sales numbers like these, imagine the number of healthy intestines walking around.

The technology behind probiotics has come with years of research developing specific strains from the most common species of Lactobacillus, Bifidobacterium and Streptococcus. “Each bacterial strain has unique benefits for GI (gastrointestinal) health, which have been documented through clinical trials,” says Marilyn Stieve, senior product manager, Chr. Hansen, Inc., Milwaukee. “L. acidophilus implants in the small intestine while Bifidobacterium implants in the large intestine. Using a combination of probiotics helps maintain balance throughout the GI system.”

Another way to look at probiotics, beside their link to intestinal health, is their effect on overall immunity. With 80% of the body’s immunoglobulin-producing cells located in the small intestine, the GI tract is the largest immune organ. Researchers believe probiotics influence our immune response through interaction with and adhesion to the GI tract.

How can these bacteria propagate in a dairy product and then survive in the intestinal environment? “Optimum conditions for growth of probiotic bacteria is pH 5.5 to 6.5 at 37° to 40°C, in anaerobic conditions,” says David McCoy, Ph.D., principal scientist, Chr. Hansen, Inc. Once yogurt is inoculated with a culture, it then incubates for about 5 hours at 37¾ to 40¾C, using lactose as its food source and converting that to lactic acid. This lactic acid results in a drop in pH and the formation of a milk-protein gel. Once the yogurt attains a pH of 4.6 to 4.7, processors cool it to refrigeration temperatures to stop the growth of the culture. Refrigerated temperatures should maintain the bacteria levels during yogurt’s typical 30-day shelf life. The recommended daily dose of probiotics is 108 to 109 colony-forming units (CFU), “so inoculation rates will vary depending on the serving size,” says Stieve.

Dairy products are good carriers of probiotics for other reasons in addition to their pH and heat sensitivity. “Dairy products provide buffering against stomach acids, helping to increase the number of cells that reach the intestine,” says McCoy.

With the benefits probiotics offer, it’s hard to believe that immune health has been so slow to catch on in this country. Probiotic-fortification of dairy products is much more widespread in Europe and Asia. “There is much greater use of structure/function claims associated with probiotic use in these countries, as compared to the implied claims commonly used in the United States,” says Stieve.

Once you have your probiotics and have eaten them too, there is a group of ingredients that you should consider as a perfect complement. “There is a growing focus on products that contribute to digestive health, like symbiotic dairy foods that incorporate both prebiotics and probiotics in yogurt and frozen desserts,” says Donna Brooks, product manager, Danisco USA Inc., Ardsley, NY.

Prebiotics, such as polydextrose, inulin, acacia gum and other fiber sources, contain carbohydrates that are not metabolized upon reaching the colon. The growth of Bifidobacterium in the large intestine depends on these carbohydrates as a source of energy, hence the term “bifidogenic.” Bifidobacterium liberates lactic acid, acetic acid and other short-chain fatty acids, which creates an acidic environment that inhibits the growth of pathogenic bacteria from species such as Clostridium and Enterococcus. Most of these fibers have a very high level of soluble fiber, which is important for Bifidobacterium growth; one well-known example is polydextrose.

“Polydextrose is a reduced-calorie ingredient containing 90% fiber and functions as a prebiotic sustainable throughout the colon,” says Brooks. Putting fiber on the ingredient legend of a dairy product was typical only for reduced-sugar or reduced-calorie products.

“Polydextrose has the advantage of many years of use in dairy products because of its neutral taste and ability to replace sugar, and still provide a smooth texture and creamy mouthfeel,” she explains. Lactitol, a sugar-free sweetener derived from lactose, also benefits digestive health. “Using a combination of polydextrose (for fiber enhancement) and lactitol to develop frozen desserts such as ice creams, sorbets, and popsicles, also qualifies them for sugar-free, no-sugar-added and low-calorie claims,” Brooks notes.

Another dietary fiber source is acacia gum, frequently referred to as gum acacia or gum arabic. “Our acacia-gum product is a tree exudate that is all-natural, GMO-free, and 100% acacia gum with a minimum of 90% soluble dietary fiber on a dry basis,” says Sharrann Simmons, vice president and general manager, Colloides Naturels, Inc., Bridgewater, NJ. The company also offers an organic acacia gum for organic dairy products.

Acacia gum can function as a stabilizer, emulsifier and gelling agent, in addition to providing an excellent source of soluble fiber. Due to its low viscosity and bland flavor, the ingredient has no special formulation or processing requirements to add it into dairy products such as yogurt, milk, dairy-based beverages or even cheese.

“The functionality and consistency of acacia gum can be enhanced by selecting from different sources and regions, thus eliminating the natural variation that occurs in different crops,” says Simmons. Acacia gum has some advantages over other similar ingredients. “Acacia gum is noncariogenic and has a low glycemic index, without the laxation effect found in other sugar-free ingredients such as sugar alcohols,” says Sebastian Baray, technical manager, Colloides Naturels International, Rouen, France.

In the future, there may be added benefits to consider when fortifying dairy products with acacia gum. “New clinical research indicates that acacia gum may enhance calcium absorption, an important benefit for dairy products,” says Simmons.

In some parts of the world, the news has led to applications in yogurt. “It is quite popular in Europe to use an acacia gum as a prebiotic in combination with the probiotics in yogurt to provide nutritional benefits, as well as a smoother texture and flavor,” says Baray. This popularity may catch on yet in the U.S. market. “As more dairy products are developed for different gender and age groups in the future, acacia gum is well designed to meet the nutritional needs for all of these groups,” says Simmons.

One fiber source showing up on ingredient legends all over the cultured-products aisle is inulin. “Dairy products are perfect food systems for inulin because it helps to enhance calcium absorption and can mimic the mouthfeel of fat in low-fat dairy applications,” says Bryan Tungland, vice president, Scientific & Regulatory Affairs, Sensus America LLC, Monmouth Junction, NJ. Inulin has no appreciable taste or color, generates very little viscosity and enhances nutritional value without adversely affecting organoleptic qualities. The company’s inulin, made from chicory root, is all-natural; GMO-free; FDA-, GRAS- and USDA–approved; and kosher-certified.

Due to its functional and nutritional properties, inulin allows the production of dairy products without adding fat calories, improving overall nutritional value without sacrificing eating quality. “Fortified milk containing inulin gains all the benefits of the prebiotic fiber and improved calcium absorption, while also delivering a full-fat mouthfeel in fat-free products,” Tungland notes. Drinkable yogurts include inulin to improve mouthfeel, to add prebiotic fiber and to help improve calcium absorption. Fermented milks use inulin as a selective food source for probiotic cultures.

Another prebiotic fiber shown to increase calcium absorption by greater than 50% are short-chain fructooligosaccharides (scFOS). According to Denise Wagner, public relations and communications specialist at GTC Nutrition, LLC, Golden, CO, more than 200 scientific studies support the benefits of the company’s scFOS. The list includes enhanced immune and intestinal function, zero glycemic index, cold-water solubility, lack of viscosity, low calories, fat-mimetic properties, and thermal stability with no Maillard browning.

A new ingredient in this category, invented by GTC Nutrition and Marigot Group Ltd. of Ireland, combines scFOS with plant-derived sea minerals to make a unique prebiotic mineral formulation.

Just when you think you can’t possibly add even one more healthful ingredient to dairy products, there are still more from which to choose. Phytosterols, or plant sterols — sterols found in plant-cell membranes — are a more novel way to fortify dairy products. Structurally related to cholesterol, plant sterols are unsaturated. Hydrogenation saturates sterol molecules so they become stanols.

Though the level of plant sterols in a typical diet is high, they have a low absorption rate in the body, as compared to cholesterol. Plant stanols have about one-tenth the absorption rate of sterols. Plant sterols and stanols lower serum cholesterol by inhibiting the absorption of cholesterol from the digestive tract. Esterification with vegetable fatty acids can improve the absorption of plant stanols.

FDA GRAS-approved the first plant stanol esters in 1999, and approved a health claim for stanols and sterols in 2000. “The current FDA requirement to make the health claim ‘Proven to reduce cholesterol’ can be met with 3.4 grams per day of stanol esters in at least two servings, which is equivalent to consuming 2 grams of stanols per day,” says Bob Bassett, key account manager, Raisio Life Sciences, Summerville, SC. “Most of the time, we would recommend consuming the recommended 2 grams of stanols in two servings, and consuming the fortified food with a meal because the cholesterol reduction seems to work best during the digestive process,” he adds. Clinical trials have shown that consuming 2 grams of stanols per day in esterified form reduces LDL cholesterol by up to 14%.

Stanols incorporate easily into dairy products. Stanol esters have a melting point of about 35°C; at room temperature they have a waxy consistency. Like other fats, stanol esters are susceptible to oxidation during storage, but they are very stable to typical processing conditions for foods.

With the original technology developed in Finland, Europe has taken the lead on fortifying dairy products with stanol esters. More than 30 products have debuted since 1999, from cream cheese and process cheese, to yogurt and yogurt drinks, to butter and milk. “One of the newer products on the market in Portugal, Spain and Switzerland is a drinkable yogurt with a full day’s dose of stanols in one serving,” says Bassett.

Processors can add the well-known phytochemicals, isoflavones, to dairy products with benefits for the heart, bones or menopause symptoms. Although soy ingredients are often viewed as “dairy alternatives,” soy proteins have applications in dairy formulations.Dairy health claims have focused on calcium and bone health, while soy health claims have focused on heart health. Combining the consumer image of dairy products and soy ingredients makes for an interesting but healthy marriage. “With the increasing popularity of soy, we are seeing more hybrid (dairy/soy blends) products,” says Charles Barber, beverage application technologist, ADM, Decatur, IL.

The development of soy-containing dairy products often relies on the use of many of the same ingredients as conventional dairy formulations. “Stabilizers, such as carrageenans, cellulose gels and gums, are quite standard and do not compromise the soy proteins in any way,” says Barber. Cultured products, such as yogurts and sour cream, need added fermentable sugars; again, this has no affect on the soy. “We can capitalize on the functionality of the soy protein concentrates and isolates to impart desired viscosity characteristics and build body into a given product,” he adds.

Though the consumer may wish for up to 100% of the daily value of many nutrients in one serving, taste, texture and appearance should be the primary concerns for formulators. Whatever the fortification goal, be confident that there is an ingredient that can function in the dairy application. Innovation has been in the vocabulary of dairy-product manufacturers for some time.

Kimberlee J. Burrington is the whey applications program coordinator for the Wisconsin Center for Dairy Research in Madison, WI. She received her Bachelor of Science and Master of Science in food chemistry from the University of Wisconsin-Madison. Her industry background is in bakery and dairy.

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