Dairy Ingredients For Health

  Calcium's role in helping build strong bones and teeth during the growth years has been evident for quite some time. Now, new research indicates that calcium may play a greater part in the health of all age groups. The body stores 99% of its calcium in the bones and teeth. The remaining 1% is found in the blood and soft tissues. This 1% aids in normal muscle contraction, blood clotting and nerve functions. The two ways of maintaining the necessary amount of circulating calcium are through the diet and from the bones - if the diet does not contain enough calcium, the body automatically takes calcium from the bones.

  Recent research indicates that calcium may also affect numerous medical conditions. Several studies, including one in the American Journal of Clinical Nutrition, have suggested that calcium intakes of 1,500 to 2,000 mg per day protect against colon cancer, especially for individuals at high risk for developing the disease. A recent article published in the Annals of Internal Medicine concluded that a diet high in calcium reduces urinary excretion of oxalate, which is believed to lower the risk of kidney stones. In this study, intake of dietary calcium from dairy products was inversely associated with risk for kidney stones, and intake of supplemental calcium was positively associated with kidney-stone risk.

  Another study, done at Purdue University, West Lafayette, IN, showed that women who consumed 1,000 mg of calcium daily lost 7 lbs. over the course of two years, while those who ingested less calcium gained weight. Calcium also plays a role in protecting against osteoporosis, essential hypertension, gestational hypertension, hypercholestemia and breast cancer. Also, the 1997 Dietary Approaches to Stop Hypertension (DASH) study determined that a diet combining lowfat dairy products and fruits and vegetables can significantly lower blood pressure.

  "Diets low in calcium are low in many other essential nutrients," says Gregory Miller. Ph.D., vice president of nutrition research, National Dairy Council, Rosemont, IL. Everyone knows that milk is a great source of calcium, but it also contains seven other essential nutrients, each at concentrations greater than 10% of the Daily Value. These nutrients are protein, vitamin D, potassium, vitamin B₁₂, riboflavin, niacin and phosphorus. They help the body maintain normal blood formation, eyesight, strong bones and muscle function, and also aid in the maintenance of the immune system, kidneys and heart.

  "The FDA defines a food as a 'good source' of a nutrient if it has 10% to 19% of the Daily Value for that nutrient per reference amount of the product," says Emerita Alcantara, vice president, nutrition and regulatory services, Dairy Council of Wisconsin, Westmont, IL. "A food is an 'excellent source' or 'high in' if it has at least 20% of the Daily Value," she adds. Zinc, magnesium, vitamin B₆ and folate are also important nutrients in milk. "Milk is the number two food source of vitamin B₁₂, the number three source of zinc, the number one source of magnesium, and the number five source of folate among U.S. adults," says Miller.

  Obtaining calcium through foods, as opposed to a single supplement, has the added benefit of increasing the intake of all these other nutrients. If an individual gets 75% of their requirement of calcium from dairy products, they also get almost 90% of their daily requirement of phosphorous, one-third of the requirement for magnesium, and one-fifth of the requirement for zinc. All of this, while consuming only one-sixth to one-tenth of the body's energy needs. "It is important to meet your dietary needs through foods because there may be modifying factors in foods that also make nutrients more available to the body, in comparison to taking supplements," says Miller.

  So, if you're not a milk drinker, how else can you get the nutrition in milk?

  Cheese contains roughly half the original solids, essentially all of the casein, very little or no lactose, most of the milkfat, and many of the vitamins and minerals of the original milk. "In general, hard cheeses are an excellent source of calcium and a good source of protein," says Alcantara. Many processed foods contain cheese and other common milk-derived ingredients such as nonfat dry milk and whey ingredients. These ingredients deliver many of the nutritional components of milk, but at lower concentrations in the finished food.

  When fortifying a food product with a specific component from milk for a health benefit, there are many ingredients to choose from - naturally derived milk calcium, for example. "Milk calcium is an ingredient that has a calcium-to-phosphorus ratio similar to that found in milk and bone," says Stacey Goebel, technical sales manager, Avonmore Waterford Ingredients, Inc., Monroe, WI. The ratio is typically 0.52:0.55 calcium to phosphorus. "In most applications, milk calcium can be easily added up to 40% of the Recommended Daily Intake for calcium," she says.

  If a food scientist is interested in making a calcium and osteoporosis health claim, there are several qualification requirements. "Two of the most important are that it contains a high level of calcium - at least 20% of the Daily Value per reference amount; and that it does not exceed any of the FDA disqualifying levels - 13 grams of total fat, 4 grams of saturated fat, 60 mg of cholesterol, or 480 mg of sodium per reference amount," says Alcantara.

  Research has shown that milk calcium deposits effectively in the bone. Animal studies, as well as human studies, indicate that milk calcium exhibits improved bioavailability over other sources of calcium, such as calcium carbonate. Bioavailability refers to how much of a nutrient in a food can actually be extracted by the body in a useable form. Proteins and vitamins are metabolized, and thus consumed, as the body utilizes them, while minerals remain unchanged as they perform their biological functions. Whether or not minerals are actually used depends upon if they are in a useable form and if they are needed to build tissue mass such as bone. "Milk calcium also typically contains low levels of lactose, which stimulates the transport of calcium for intestinal absorption," says Goebel. In one study, it was suggested that the protein in a milk-calcium product, typically whey protein, allowed more protein-mineral complexation, which improved the bioavailability of the calcium and phosphorus. "Functionally, the whey protein in milk calcium aids in the solubility of the product," says Goebel.

  Either dairy calcium or inorganic calcium (calcium carbonate) can be combined with protein isolates. "What you're getting there is the calcium and the functionality," says Lee Huffman, Ph.D., technical service manager, New Zealand Milk Products (North America) Inc., Santa Rosa, CA. "Calcium can be problematic in formulation - it settles out, tastes gritty. We're addressing a processing functionality issue with a huge benefit in nutrition." If it's a source of protein and calcium that you're looking for, milk proteins are some of the best choices available.

  Whey proteins are heat-sensitive, so most are processed at lower temperatures to minimize denaturation. On the other hand, caseins are denatured by acid; "that's how you get the casein from milk," Huffman notes. "They're totally different from a globular whey protein; they are a random coil, so casein is heat-stable. At neutral pH, caseins are soluble; you take it down to a pH of 4.6, their isoelectric point, they become insoluble. Back up to pH 7, they're soluble again."

  If a protein coagulates, its nutritional value remains virtually the same, although there may be slight differences - a denatured protein might have a digestibility of 97, as opposed to 98 for the undenatured product, for example. Sometimes "denatured" is linked in people's minds with "less digestible." This has been a huge issue in the sports area lately, in fact, with some thinking that if you heat a protein, it's not accessible to the body. But although there are some extreme conditions of heat, pH and time that can make amino acids unavailable to the body, those conditions are not used in processing ingredients. However, while differences between denatured and undenatured forms are negligible nutritionally, product designers must remember that differences will show up in functionality.

  Casein proteins form a micellular structure by incorporating calcium and phosphate ions, thus providing a source of phosphopeptides. The enzymatic hydrolysis of casein can produce a compound called casein phosphopeptide. "Casein phosphopeptides enhance the absorption of calcium by forming soluble complexes," says Andrew Corker, product manager, bioactives, DMV International Nutritionals, Fraser, NY. "Approximately 375 mg of casein phosphopeptide is required to solubilize 100 mg of calcium," he says.

  With 75 million people suffering from the effects of osteoporosis in Europe, Japan and the United States, improving calcium absorption is a concern. Other minerals such as iron, manganese, copper and selenium can also be sequestered by casein phosphopeptides. Some current applications include toothpaste and other personal hygiene products. Potential applications include calcium-enriched tablets, chewing gums, instant drink mixes, liquid formulas, UHT milk, confections, and a number of other fortified products.

  If a product developer is looking for a protein source for a special dietary need, such as non-allergenicity, milk-protein hydrolysates are an excellent choice. "Both whey proteins and casein can be hydrolyzed with specific enzyme blends to varying levels of hydrolysis," says Abbie More, product manager, hydrolysates, DMV. As the level of hydrolysis increases, the digestibility, nitrogen absorption and retention also increase, and the allergenicity of the protein decreases. "A product with low to moderate levels of hydrolysis is well suited for sports nutrition products, protein tablets and instant drinks," says More. Medium and high hydrolysis levels are targeted for clinical, enteral and infant-formula applications. "A product with a high level of hydrolysis is designed for non-allergenic applications like special infant formulas," she adds.

  Whey proteins have one of the highest biological values as compared to other protein sources such as egg, milk, beef, soy and casein when measured according to the protein efficiency ratio (PER) method.

  Another method, now the standard in many cases, is the protein digestibility-corrected amino acid score (PDCAAS). This method also ranks whey-protein isolate as one of the best protein sources, assigning it a score of 1.0. This method does not account for any amino acids in excess of the requirements of the human body. (For more information on evaluation of the nutritional value of proteins, see "Protein Possibilities" in the October 1997 issue of Food Product Design.)

  "Whey has an excess of essential amino acids," says Huffman. Casein does also, but they have a slight difference in protein digestibility - maybe less than 1% difference. What the PDCAAS method doesn't do is go beyond and look at some of the individual components that may be important. "When using a milk-based protein, there's also other nutritional components that come along with it," says Huffman.

  The level of essential amino acids in whey proteins exceeds all other sources such as egg, casein and soy; the essential amino acids make up approximately 60% of whey's total protein content. Whey contains a particularly high level of leucine and lysine, as compared to soy-protein isolate or dehydrated egg white, and is a good source of the sulfur-containing amino acids cysteine and methionine. These amino acids maintain antioxidant levels in the body, and are thought to stabilize DNA during cell division. Animal studies with total whey protein have shown beneficial effects on chemically induced cancers, stimulation of the immune system, and increases in life span. In other animal studies, whey proteins were able to lower LDL cholesterol and promote the release of cholesystokinin, an appetite-suppressing hormone.

  Sports beverages utilize whey-protein isolates and whey-protein concentrates for their balance of protein fractions. "Athletes choose products with whey proteins for quick absorption and muscle repair," says Julie Wagner, director of applications, Century Foods International, Sparta, WI. "The categories that incorporate whey proteins as a part of their nutritional profile are very-high-protein products (20 to 24 grams of protein per serving); meal replacements; weight-gain products; and pre-workout drinks," she says. Each category is designed for specific benefits to an athlete or body builder, such as providing quick energy for a workout, adding calories for weight and muscle gain, or for recovery from a workout and muscle repair. "A formulator needs to consider the metabolism requirements and taste preferences of individuals when formulating sports beverages," adds Wagner.

  Another advantage to formulating with whey proteins is the high level (nearly 26%) of branched-chain amino acids (BCAAs). These can provide a benefit for athletic beverages or other products designed to provide energy for those who undergo intense or prolonged exercise. The BCAAs (leucine, isoleucine and valine) directly supply energy to the skeletal muscles during extensive exercise, rather than first being metabolized through the liver like the other amino acids. Since the body's demand for these three amino acids increases during exercise, athletes who want to preserve muscle mass like to increase their consumption.

  Even more exciting news is associated with the biological activity of the individual whey proteins. Beta-lactoglobulin is considered a retinol-binding protein thought to bind vitamin A and supply this vitamin to the newborn. Only the milk from animals that depend on passive immunity contains ß-lactoglobulin. It is thought that it may have other roles in addition to retinol binding, such as regulating milk synthesis. Both ß-lactoglobulin and a-lactalbumin influence mitotic activity in the mammary gland and protein-synthesis capacity; ß-lactoglobulin is also the major allergen in milk.

  The main biological role for a-lactalbumin is lactose synthesis in the mammary gland. It also binds metal ions such as calcium, and there's been some research that indicates this protein has anti-tumor effects as well.

  "Lactoferrin sequesters the iron in milk, thus naturally extending its shelf life by making the iron unavailable for bacterial growth," says O'Donnell. Lactoferrin's ability to bind free iron enables it to function as an antibacterial agent in the body as well. The action of specific proteases, such as pepsin, can convert lactoferrin into a compound called lactoferricin, which possesses broad-spectrum activity against pathogenic bacteria and yeast. "Lactoferrin can be manufactured with varying iron contents to differentiate and enhance its bioactive properties," says Goebel. All types are recommended to enhance the immune system and promote intestinal cell growth. The lowest level of iron content can provide unfavorable conditions for gram-negative bacteria, while the highest levels are well-suited for binding and transporting iron.

  "Lactoferrin's functionality in the body makes it ideal for applications like infant formula, nutritional bars, and sports and performance products," says Goebel. Some of the interest in infant-formula applications originates from the comparison of human milk to bovine milk. Two proteins that occur at higher levels in human milk than in infant formula are a-lactalbumin and lactoferrin. Lactoferrin concentration in human milk is 0.20 grams per 100 ml, and 0.01 grams per 100 ml in mature cow's milk.

  Lysozyme and lactoperoxidase are also effective antibacterial proteins. Lysozyme works to extend the shelf life of milk via hydrolysis of glucosidic linkages in the peptidoglycan of bacterial cell walls. The alkalinity of this enzyme, which is also found in tears and saliva, contributes to its antibacterial activity. Lactoperoxidase catalyzes the oxidation of thiocyanate to hypothiocyanate via hydrogen peroxide. It is part of a complex that works against gram-negative bacteria such as Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa. The lactoperoxidase system is being used for acne preparations, shampoos, toothpaste, soft-serve ice cream, and pastry cream.

  For maximizing bioactivity, there's even more to be gained from induced bioactive milk components. Many induced bioactive peptides with either casein or whey-protein precursors have been identified in milk. The peptides derived from caseins are called casomorphins. Some are opioid agonists, meaning that they bind to opioid receptors and exhibit morphine-like functions. Some, derived from lactoferrin or k-casein, are opioid antagonists, meaning that they suppress the agonist activity of enkephalin and have an effect on smooth muscle. These phosphopeptides are also considered induced bioactive peptides, and have the function of carrying minerals. Glycomacropeptide is formed during the cheesemaking process from the reaction of chymosin with k-casein. Whey protein consists of 15% to 20% glycomacropeptide.

  "Whey-protein isolate (WPI) that has been manufactured by microfiltration contains the glycomacropeptide protein fraction, while WPI manufactured by ion exchange does not retain this fraction," says Wagner. The microfiltration process also retains more calcium, phosphorous and potassium, with less sodium in the final product. "Glycomacropeptide has been shown to stimulate the synthesis and release of cholesystokinin in the body," she adds. Cholesystokinin plays a role in the regulation of digestion and functions as an appetite suppressant.

  Immunoglobulins are considered an important bioactive component in whey. Colostrum contains very high levels of immunoglobulin G (IgG). Immunoglobulins are commercially available, and have applications in treatments for AIDS-related symptoms such as cryptosporidia diarrhea. Although all of these components are found in whey, many are not commercially isolated from whey due to economics. Specific doses and their benefits have not yet been resolved for the purpose of regulatory approval for most of these protein fractions.

  Colostrum has been on the market as a health-food product for a number of years. It's not milk, but the pre-milk fluid from a cow just before and after calving. Its effects, for the most part, are anecdotal, although some studies have been conducted. The driving factor is that it's high in immunoglobulins and that it might confer some health-enhancing properties. Dehydrated colostrum is similar to nonfat dry milk, although higher in protein content and immunoglobulins.

  "Milkfat is the most complex fat system known to man," says O'Donnell. Recent research indicates that milkfat contains potential anticarcinogenic components, including conjugated linoleic acid (CLA), sphingomyelin, butyric acid and ether lipids.

  CLA consists of one or more positional and geometric isomers of linoleic acid (cis-9, cis-12 octadecadienoic acid). CLA's conjugated double bonds are usually at positions 9 and 11, or 10 and 12, with each double bond either in the cis or trans configuration. Australian studies published by the American Society for Nutritional Sciences showed that CLA inhibited proliferation of human malignant melanomas and colorectal, breast and lung cancer cell lines. In animals, results included reduced incidence of chemically induced mouse epidermal tumors, mouse fore-stomach neoplasia, and aberrant crypt foci in rat colons.

  Sphingomyelin is a phospholipid located in the outer leaflet of the plasma membrane of most mammalian cells. In cow's milk, phospholipids represent 0.2 to 1.0 gram per 100 grams of total lipids, and are associated with the milkfat globule membrane. When milk is processed, this membrane is disrupted, and the phospholipids can relocate to the aqueous or serum phases. The amount transferred depends upon the type and severity of the processing. Sphingomyelin comprises about one-third of the total milk phospholipids.

  "Butyric acid has been shown to regulate cell death by inhibiting uncontrolled proliferation and supporting normal apoptosis (normal cell death), in a number of cancer cell types, says O'Donnell.

  Both human milk and cow's milk contain lactose. Lactose is a disaccharide consisting of the monosaccharides glucose and galactose. Dietary lactose is not absorbed intact, but must be hydrolyzed in the small intestine by the intestinal enzyme lactase. Lactase activity is high until a child is weaned, and then declines in many population groups.

  Lactose intake does not induce lactase activity. Decline in lactase activity is often called lactase nonpersistence, lactose maldigestion or primary lactase deficiency. Lactase deficiency is defined as congenital, secondary or primary. Congenital deficiency is extremely rare, and is diagnosed when the lactase enzyme is absent or severely reduced throughout life. Diseases or damage to the intestinal mucosa, where lactase is active, causes secondary lactase deficiency.

  Primary lactase deficiency is the most common form, and the decrease in lactase activity is one factor influencing whether symptoms of lactose intolerance develop. Lactose intolerance is characterized by the development of symptoms including abdominal pain, bloating, gas and diarrhea.

  Self-diagnosis is not recommended, because it could lead to a loss in nutrition or failure to detect more serious gastrointestinal problems. A typical clinical test used is called the breath hydrogen test. It measures the amount of hydrogen gas formed by the fermentation of any undigested lactose by the bacteria in the colon. A dose of 50 grams of lactose in aqueous solution (equivalent to the amount in one quart of milk) is typically used in this case. "Studies have shown that many individuals judged to be lactose intolerant according to clinical tests can consume one cup of milk with no problem," says Alcantara. "One important reason is that an 8-oz. serving of milk provides 12 grams of lactose, which most individuals can handle, especially when consumed with a meal," she adds.

  The prevalence of lactose maldigestion appears to vary widely among different racial and ethnic groups. In the United States, lactose maldigestion is estimated to be about 6% to 19% in whites, 53% in Mexican Americans, 62% to 100% in Native Americans, 80% in African Americans, and 90% in Asian Americans. Many of these adults may not necessarily experience the symptoms of intolerance, however.

  "Many people can avoid problems related to lactose maldigestion by drinking milk with a meal, eating aged cheeses, or eating yogurt with active cultures," says Miller. Typically, whole milk and chocolate milk are better tolerated than lower-fat milks. Ice cream and cheeses such as Cheddar, Colby, Swiss, Parmesan and cottage cheese may be tolerated better than milk because of their lower lactose content. Oral lactase enzyme supplements, when ingested before consuming dairy foods, may also work well for some people.

  The dairy industry is beginning to use "protein fractionation" to separate out some of the bioactive components found in dairy proteins. "We've had the technologies for years," Huffman says. "But having the technology be cost-effective so that the ingredients are economical enough for consumers is just starting. Now that processors can make isolates economically, the next step is to fractionate the components." This is happening with both casein and whey protein, she says. "There are some commercial fractions that have been isolated. One is lactoferrin, the other is lactoperoxidase." These are popular in Asia because of high interest in functional foods, and because the consumer is willing to pay higher prices for the products.

  Product designers may want to keep an eye out for a-lactalbumin-enriched whey protein, ß-lactoglobulin-enriched whey protein, casein phosphopeptides and various peptides from hydrolyzed protein. But dairy science won't stop with improved processing; they'll go straight to the cow. "In the future, scientists will be able to modify the expression level of genes in the cow, to selectively change the milk's nutritional and functional properties," says O'Donnell. Imagine the ability to produce a cow's milk for infants that is more like human milk, with the absence of ß-lactoglobulin and increased levels of lysozyme and lactoferrin. Increasing the concentrations of lysozyme and lactoferrin could also possibly increase the shelf life of milk. Or how about developing lactose-reduced milk for those with lactose intolerance?