More Than Just Milk

More Than Just Milk
January 1998 -- Design Elements

By: Kimberlee J. Burrington
Contributing Editor

  When it comes to today's dairy ingredients, "value-added" encompasses a whole new list of products with an even wider range of functionalities and applications. That daily glass of milk can be heated, concentrated, fermented, separated, isolated, fractionated and dried into a tank full of functional and nutritional ingredients, many of which have already found their way into foods currently being consumed. The dairy industry faces the challenge of providing high-quality products along with some practical knowledge about their use in food applications, giving food designers the opportunity to learn about an exciting new generation of ingredients that is backed by sound research.Milk it  The list of ingredients that include the casein proteins of milk are: nonfat dry milk, caseinates, caseins, milk protein concentrates and milk protein isolates. Although they all have areas of application, the ones recently receiving the most attention from the researchers and the producers are the caseinates, milk protein concentrates and milk protein isolates.  Caseinates are produced from skim milk by adding acid or microbial cultures to precipitate the casein from the whey at pH 4.6. The precipitated casein is then washed with water and resolubilized with alkali or alkaline salt to form caseinate. Sodium and calcium caseinates are the most common, with some of the specialty caseinates including combinations with potassium or sodium and calcium. A food designer can expect high solubility; low viscosity; clean flavor; excellent emulsification capacity; high fat and water-binding capacity; and freeze-thaw stability from the caseinates. These physical properties make them good candidates for coffee whiteners, cream liqueurs, baked goods, dry mix beverages, soup mixes and comminuted meat.  The milk protein concentrates include the ingredients produced from skim milk, and contain 56% to 82% protein. They contain casein and the whey proteins, some fat, minerals, vitamins, and less lactose than nonfat dry milk. Complete with a clean, milky flavor, they are ideal for nutritional, bakery and frozen dessert applications.  The milk protein isolates are a co-precipitate of casein and whey proteins that range in protein from 89% to 94%. Milk protein isolates contain essentially all of the proteins from skim milk in a soluble form and possess a high nutritional value. This type of ingredient can be used and modified to maximize its functionalities in a wide range of products. Ideal for nutritional products, milk protein isolates include beverages, liquid supplements, puddings, sauces and bars as target applications in this market. Other processed foods - cream cheese, cheese-spread analogs and batter coatings - give milk protein isolates more product areas to expand their functional properties. Like the milk protein concentrates, their bland, milky flavor provides a real benefit.  "The three attributes which make milk protein isolates and milk protein concentrates a good choice over other protein ingredients, are price, functionality and flavor," says Ralph Knights, Ph.D., product development manager, New Zealand Milk Products, Inc., Santa Rosa, CA.Upping the calcium  Another category of milk protein ingredients has been developed: those that are calcium-fortified. Calcium can be added to caseinates and milk protein concentrates to bring it into applications that previously have been difficult to fortify. These ingredients make insoluble calcium dispersible and suspendable. The calcium-to-milk protein ratio can be formulated higher than any ingredient other than calcium salts. Depending on requirements, calcium levels of these ingredients can range between 2.7% to 15.0% of total weight to provide 100% of the RDI in some food systems. With the current health concerns about calcium consumption and osteoporosis, these new milk proteins offer the product developer the potential to fortify current formulas or add calcium to foods not typically fortified with the chemical element.  Product designers can expect the same high level of functionality from calcium-fortified milk proteins as from their unfortified counterparts. "The main markets for milk-derived fractions will continue to be functional, good-tasting ingredients for processed foods," Knights says.  Another unique ingredient is a high-calcium fractionated whey. A joint study with Davisco Foods International, Inc., LeSueur, MN, and the American Institute of Baking showed that this source of calcium received the highest relative calcium bioavailability in rats as compared to three other common calcium sources. The other three sources of calcium were: calcium carbonate, commonly used in fortified foods; calcium lactate, an organic source of calcium often prescribed as a supplement; and calcium citrate, used in over-the-counter calcium supplements.The right whey  Most people have heard about whey, the serum or watery portion of milk that remains after the manufacture of cheese. It is called "sweet" whey (pH greater than or equal to 5.6) if it comes from rennet-coagulated cheese manufacture or "acid" whey (pH less than or equal to 5.1) if it originates from cottage cheese manufacture.  Whey contains lactose, minerals, vitamins, protein and traces of fat. Dried whey composition is 13% protein, 76% lactose, 1% fat and 10% ash. With such a nutritional list of ingredients, is there any wonder that isolating these components might be useful? Although many food uses exist for whole dried whey, efforts to improve the functionality and utilization of whey have led to more concentrated and specialized forms. "Suppliers of whey-derived ingredients have the ability to customize their products for specific functional needs," says Bill Haines, Ph.D., vice president of product research and technology transfer, Dairy Management, Inc., Rosemont, IL.  The most valuable component of whey is the whey proteins. Ultrafiltration and diafiltration membrane technology have provided the means to further concentrate and separate whey components. The protein and fat (retentate) in the whey are separated from the lactose and minerals (permeate) by these processes. Once whey is dried, a producer can provide "whey protein concentrates," or WPCs, with protein levels from 34% to 90%.  WPCs have been around for years, but product developers can expect better performance today. "Improvements in the design of membrane systems used to produce WPC are reflected in the quality of the final product," says Karen Smith, Ph.D., R&D manager for Wisconsin Whey International, Madison, WI. "Also, more and more cheese producers are viewing whey as a source of revenue and, therefore, are handling the whey in a manner that preserves its quality for WPC manufacture."  A higher quality product means improved functionality for the product developer. Some of the basic properties that a WPC can provide in a food application are whipping/foaming, emulsification, high solubility, gelation, water-binding, and viscosity development. Generally, WPCs with higher protein content have improved functionality over those with lower protein content.  Some very exciting work in progress involves the use of 34% WPC in various food applications. This demonstrates their ability to work well in some applications, but not in conflict with the applications designed for the higher protein ingredients. High solubility over a wide pH range makes WPCs a good candidate for a sports beverage or meal-replacement beverage. Their water-binding capabilities also make them suitable for processed meats, cakes or breads.  Typically WPCs will provide more than one functional purpose for food applications. Gelation characteristics will increase WPC benefits in some of the same products that profit from water-binding. Salad dressings, coffee whiteners, soups, cakes, infant formulas and sausages all can utilize the emulsification abilities of WPC. They also address the functional needs of viscosity in products such as soups and gravies. Cakes, desserts and whipped toppings can always use the added foam stability of a WPC.  Depending on a food designer's needs, a suitable WPC exists for various applications. A number of factors that influence their functionality are the whey source, protein content, amount of heat treatment received during manufacture, and lipid and mineral content.  "If you can work with the inherent properties of a protein ingredient, that is where you want to be for functional applications," says Lee Huffman, Ph.D., technical service manager, research and development, New Zealand Milk Products.  Whey protein conformation and functionality are interrelated and dictated by changes in their globular folded structure. Their functional properties are affected by several factors within a food application, including concentration, state of the whey proteins, pH, ionic environment, (pre-) heat treatment and the presence of lipids.  In the native state, whey proteins are highly soluble and adeptly perform emulsification and whipping functions in a food application. However, heating whey proteins can result in a loss of solubility due to denaturation of the proteins, especially in the pH range of 4.0 to 6.5. While solubility is adversely affected by heat, emulsification can be improved through controlled heat denaturation of the protein. As the whey protein unfolds, hydrophobic amino acid residues are exposed, which enhance the ability of the protein to orient at the oil/water interface. The presence of salts during the emulsification process influences whey protein conformation and solubility. In their undenatured form, whey proteins can form rigid gels that hold water and fat, and provide structural support. The formation of disulfide bonds and ionic bonding controlled by calcium ions appears to determine gel structure.  "The unique properties of the whey proteins which set them apart from other protein sources are their acid stability and ability to form clear gels," Knights says.  Water-binding capacity is a measure of the amount of water held in a gel under a specific set of conditions. The water-binding abilities of whey proteins can help reduce formula costs due to the added water being held by the proteins. Other properties associated with water-binding - swelling, gelation and viscosity - are primary determinants of texture in processed cheese, yogurt and reduced-fat foods.  Viscosity development is closely related to gelation and other protein-protein interactions. Foaming properties are best when the whey proteins are undenatured, not competing with other surfactants at the air/water interface, and stabilized by an increased viscosity when foam formation occurs. "Assuming a formulator can control the manufacturing process, the most versatile product you could give to a food formulator would be a very low level of denaturation, because it allows them to have whatever kind of process they want to have," says Ann Berres-Olivotti, manager, development and technology, Foremost Farms USA, Sauk City, WI.  For products not requiring a lot of further processing, some denaturation might prove advantageous. "In a frozen dessert mix, it is necessary to have some level of denaturation to produce a product with a good mouthfeel," Berres-Olivotti says. In this application or other dry mix applications, it is important to work with your supplier to achieve the desired level of denaturation and resulting functionality.  Whey proteins also contribute to browning by reacting with lactose and other reducing sugars present in a formulation, providing color to baked goods and sauces. Not only are WPCs functional, they also are bland-tasting and contribute no foreign or off-flavors to foods when used as an ingredient.  "When considering a change or addition to your WPC suppliers, be aware that analytical composition and performance in pure solutions may not predict how a WPC will function in your given application," Berres-Olivotti says. "You really need to test the WPC in a model food system to identify if it will work for you."  The category of specialty WPCs includes demineralized and hydrolyzed versions. "The demineralized products are often used in infant formula, while lactose hydrolyzed products work well in cheese-type spreads and yogurt," she says. In this case, the hydrolysis of the lactose into glucose and galactose allows for the addition of dairy solids with some added sweetness to the product. "For example, in spreads, a lactose-hydrolyzed WPC can be used to partially replace cheese solids, other dairy solids and corn syrup solids, enhancing the product flavor, says Berres-Olivotti. For those interested in a "no added sugar" claim, this type of WPC can also add sweetness to an ice cream or yogurt application. For product needs that are more specialized than a more common 34% to 75% WPC, some of the most exciting news is happening in the area of whey protein isolates and isolated fractions of whey.Other wheys  Research involving whey protein isolates, alpha-lactalbumin, beta-lactoglobulin, lactoferrin, bovine serum albumin, lactoperoxidase, peptides and immunoglobulins has gained recent press attention. As far back as the Middle Ages, folk medicine has acknowledged cheese whey for its therapeutic and prophylactic value. While providing unique physical, chemical and biological properties, these various ingredients have been found to provide some of the most interesting physiological benefits.  However, just because much of the research has focused on these fractions doesn't mean these benefits are isolated solely to them. "In some cases, medical research has found that even use of WPCs in the diet have proven beneficial," says Huffman.  Research is currently in progress on the use of whey protein concentrate in the diet and its anti-tumor effects for head- and neck-cancer patients. Whey protein has been shown to stimulate cell-mediated and humoral immunity; to have an antioxidant role by increasing tissue glutathione; and to improve the body's nutritional status in stressed individuals, thereby inhibiting growth of several tumor types.  Whey protein isolates (WPI) are those products with a protein content of over 90%. Various processes remove the nonprotein components. These include precipitation, microfiltration and ion exchange. The composition (protein, lactose and mineral content) and product characteristics can vary with the process used.  "We use a cross-microfiltration method to produce our whey protein isolate and that produces a slightly different protein profile," says Robert Beausire, technical sales manager, Avonmore Ingredients, Inc., Monroe, WI. "A big difference is the glycomacropeptides. They generally don't get pulled out by the ion exchange process. If you're looking at the nutritional properties, there's a lot of evidence that these are a biologically active protein with a positive effect on the digestive system. They're also a digestion regulator.  "The benefit of whey protein isolate is that it has very low lactose, less than 1%, and very low fat, less than 1/2%," says Beausire. "It has a very bland flavor so you can formulate with it in products not normally associated with dairy products, like a fruit-bar or fruit-juice application. Whey protein concentrate, while it's vastly improved due to new processing techniques, still tends to have a whey flavor in comparison."  Whey protein isolates can also be manufactured by selective ion exchange processes to select the primary functional proteins, beta-lactoglobulin and alpha-lactalbumin. They provide high gel strength, viscosity, aeration, water binding, and high solubility to an application. In their pure form, they can be used to replace other ingredients, such as soy protein, egg whites, or gelling agents. These isolates consist of completely undenatured protein and also contain up to 10% to 12% biologically active immunoglobulins, according to Polly Olson, Davisco's director of sales and marketing.  These characteristics add up to a high quality protein ingredient with a Protein Digestibility-Corrected Amino Acid Score (PDCAAS) of 1.14, a score that exceeds those reported for soy protein. The previously recognized PER (Protein Efficiency Ratio) method, which measured the weight gain of rats being fed the test protein, has been replaced by the PDCAAS. The Food and Agriculture Organization (FAO) has established this internationally recognized method to compare protein quality based on the amino acid requirements of humans. According to this method, the PDCAAS of an ideal protein that meets all the essential amino acid requirements of the human body has a value of 1.  Whey proteins can also be modified through processing or enzymatic treatments that alter their structure to provide enhanced functionality for gelation, emulsification and viscosity applications. For example, the Southeast Dairy Foods Research Center at North Carolina State University in Raleigh has developed a bioprocess that results in specific, limited proteolysis. This greatly enhances the ingredient's emulsifying activity and stability in a pH range of 3 to 9.  Several whey protein fractions have been considered as dietary ingredients, with potentially greater activity against the development of colon cancer than the total whey protein product. Lactoferrin-supplemented diets have enhanced the protective effect of total whey protein in animal studies relating to colon cancer. Clinical trials with whey protein isolate have been conducted on children with AIDS. It has been demonstrated that the ability of lymphocytes to offset oxidative damage is measured by determining the capacity of these cells to regenerate glutathione. Patients in this study who started with low blood-lymphocyte glutathione exhibited a substantial increase in glutathione content after including whey protein isolate in the diet.  Several protein fractions display antimicrobial, as well as antiviral, activity. These fractions include lactoferrin, lactoperoxidase, lysozyme and immunoglobulins. Technology has been developed on a commercial scale to produce these proteins for use as biopreservatives and as natural anti-infectious components for prophylactic and therapeutic treatment of bacterial and viral diseases.  One fraction receiving a high level of interest for its nutraceutical properties is lactoferrin. This iron-binding protein, in addition to its bacteriostatic properties, is also associated with enhanced iron absorption, stimulation of bacterial gut organisms, such as bifidobacteria, as well as a potential immune-stimulating role. It is one of the principal whey proteins in human milk, present at a level of about 30% of total whey proteins.  "The level of lactoferrin in cow's milk is less than 1%," says Beausire. "It would be cost-prohibitive to match that (human) level, but the actual levels that provide benefits are currently being researched and are believed to be much lower.  "Lactoferrin, as well as being an antioxidant, binds certain gastric pathogens and is bactericidal against a variety of pathogenic bacteria and yeasts," he adds. "This could lead to its use for treatment of intestinal ulcers and other gastric disorders. Our company is very excited about the potential applications for lactoferrin in new products, particularly in the nutraceutical market."  Not all research has focused on fractions for purely physiological functions. Currently, research is under way on the use of beta-lactoglobulin as a fat replacer in meats. Licensed technology exists for producing heat-induced, beta-lactoglobulin gels that resemble animal fat. Use of alpha-lactalbumin in infant formulas is becoming more common as research attempts to get closer to the composition of human breast milk. Alpha-lactalbumin also has been modified in attempts to perform some of the same functionalities found in egg white and its application in angel food cake.Sugary situation  Lactose or milk sugar is in abundant supply due to increasing cheese production. Lactose can be produced from whey or whey permeate. Its primary use is in bakery and confectionery products. Similar to other components of milk or whey, interest also has focused on the development and production of new lactose derivatives. The current news concerning lactose focuses on its derivatives, the galacto-oligosaccharides. Commercially successful examples are lactitol and lactulose.  Lactitol is produced by the chemical hydrogenation of lactose. Lactulose is produced by chemical isomerization of lactose. Galacto-oligosaccharides are an important part of the functional foods trend as a factor in the well-being of the digestive tract. Galacto-oligosaccharides are not digested or absorbed in the small intestine, so they reach the colon where they are fermented by beneficial colon bacteria, bifidobacteria.  Lactulose has a considerable influence in the medical treatment of some forms of liver disease, and it aids and/or restores health after bouts of salmonellosis. When used as a food ingredient to improve nutritional value, lactulose can be added to many applications, without loss of functional or nutritional properties due to processing. Some applications include: infant formulas or baby food; yogurt; diabetic sweetener; sugar substitute in confectionery products; and dried and liquid nutritional supplements for seniors.  As the nutraceutical market grows, consumers will be seeing more whey-derived ingredients on their foods. A family of perhaps more obscure products that are derived from whey, bacteriocins, comes from fermentation with lactic acid bacteria. Food-grade bacteriocins are proteinaceous antimicrobial compounds with bactericidal or bacteriostatic activity. Nisin A is one bacteriocin produced commercially and used as a food preservative in processed cheese and canned foods to prevent growth of clostridia and other pathogens. With demands for natural food additives increasing, applied research is currently focused on producing, by economically viable means, large amounts of bacteriocins for these applications. Other areas of research on whey permeate have focused on its antioxidant activity in meat products.Buttering it up  Recent studies indicate butterfat may not be as bad as its replacements. And now, butter is even better. Milkfat can be modified like other fats and oils for specific functionalities. Some of the functional attributes associated with milkfat include: flavor, flavor potential, structure formation, hardness, spreadability, layering, shortening and lubricity. These attributes are shaped through crystallization and melting characteristics, surface-active properties and nutritional properties. Individual food applications utilize different functional properties of milkfat. For instance, butter is used for its shortening properties in cookies to provide a tender texture. It is used in pastries for its layering characteristics to yield a flaky puff pastry. The triglycerides, diglycerides, monoglycerides and individual fatty acids perform a wide range of functions that can bring new functional properties to unique ingredients based on milkfat.  "The communicated needs of industry, together with the cooperative efforts of academia, have driven the development of fractionated milkfat," says Jill Cornman, director of sales and marketing, Grassland Dairy Products, Greenwood, WI. "Fractions expand the physical and functional characteristics of milkfat not available with butter."  Technology is currently in use to fractionate milkfat into its triglyceride fractions by crystallization from melted milkfat. "The applications being targeted are high-melt fractions for use by the chocolate industry for bloom prevention and a cocoa butter replacer, and the very low-melt fractions for spreadable butter, along with several fractions for use as starting materials for natural flavors," says Kerry Kaylegian, researcher at the University of Wisconsin Center for Dairy Research, Madison. "These fractions represent a range of melting points and melting profiles."  The six available fractions and their melt points are: very high melt-1, (50°C), high melt-1, (408C); middle melt-1, (278C); middle melt-2, (298C); low melt-2, (218C); and very low melt-2, (138C).  Other major areas in which milkfat fractions might be applied are in the baking and cheese industries. Some new applications involve the use of intact milkfat and milkfat fractions in the production of structured lipids, sucrose polyesters, edible films, emulsifiers, and cosmetics. Some nontraditional functionalities of milkfat include the antioxidant and anticarcinogenic properties of linoleic acid and the antimicrobial characteristics of lauric acid.  Technology exists to customize the components of milk. Whether a food designer's needs are functional or nutritional, milk-derived ingredients are up to the task.  Kimberlee J. Burrington is the whey applications program coordinator for the Wisconsin Center for Dairy Research in Madison, WI. She received her B.S. and M.S. degrees in food chemistry from the University of Wisconsin-Madison. Her industry background is in bakery and dairy.Back to top