Protein Power

Protein Power

by Kim Schoenhals

Protein intake has long been an integral component of weight management and performance nutrition, although the market for protein is expanding into the realms of heart and women's health, children's nutrition and immune function. Soy, whey and casein protein are available to enhance a variety of foods, from the mainstay bars and ready-to-drink beverages to up-and-coming applications such as snack foods and confections.

Health Benefits

Probably the most common reason manufacturers seek to incorporate protein into a functional food or beverage is the nutritional benefit. While soy, whey and casein impart distinct health qualities to food and beverage applications, they also share some health attributes, such as improving athletic performance.

In one trial, whey-protein supplementation led to significant improvements in knee extension peak torque and lean tissue mass.¹ Additional research supported by Golden, Colo.-based AST Sports Science indicated 100-percent whey protein was more effective in increasing muscle mass and strength and decreasing fat compared to casein.²

Casein may benefit athletes, exercisers and weightlifters by helping to increase strength during resistance training. Researchers at Brigham and Women's Hospital in Boston reported that compared to whey protein hydrolysate, casein protein hydrolysate led to a greater mean increase in strength in the chest, shoulders and legs.³

Comparatively, soy protein may prevent exercise-induced protein degradation in skeletal muscle, according to animal research out of Japan.⁴ Another study, which utilized Solae brand soy protein from The Solae Co., based in St. Louis, indicated soy intake (80 g/d of soy protein, 88 mg/d of genistein) protected against muscle tissue breakdown and inflammatory oxidant stress compared to whey protein intake.⁵

"Protein is useful on several levels," said Steve Rittmanic, director of product development at St. Paul, Minn.-based Protient, manufacturer of whey and soy proteins made through a membrane filtration process. "It's a basic nutrient and supplies amino acids. Also, in a functional food, there are possible benefits of some breakdown products of the proteins, like the peptides."

One of the main benefits of taking protein, especially in the realm of sports nutrition, is the amino acid content. The building blocks of protein, amino acids help repair and build muscle. Researchers have found that exercise, coupled with amino acid intake, has an additive effect on muscle protein synthesis.⁶

While all proteins are comprised of chains of amino acids, the body does not absorb them all at the same rate. Casein, for example, is digested more slowly than whey or soy. "If you look at protein as a source of amino acids for your body, taking a casein protein drink mix at 6 p.m. will allow the body to release amino acids into the bloodstream way into the night," according to Benoit Turpin, technical and national sales director at Wapakoneta, Ohio-based Euro Proteins, which supplies casein, whey and milk proteins. "That is particularly important for athletes or bodybuilders who have a very heavy breakdown of muscle tissue as they go through exercise. By taking casein protein, their body rebuilds itself overnight because of the positive flow of nitrogen and amino acids through the bloodstream."

Whey protein, on the other hand, is quickly absorbed. This is an advantage of using whey proteins, according to Turpin. "They're loaded with branched chain amino acids, which is a very sought-after quality for bodybuilders and athletes, and they can be quite inexpensive."

Soy also contains branched chain amino acids, as well as high levels of arginine and glutamine. "Some researchers think arginine and glutamine impart some of soy's performance benefits," said Belinda H. Jenks, Ph.D., FACN, director of novel health benefits at The Solae Co. "They're important for anabolism, mostly, and for supporting immune system health."

Supplemental L-arginine and L-glutamine may spare muscle proteins by combating the negative nitrogen balance and muscle wasting occurring in those with acute injury,⁷ and L-glutamine may independently reduce immunosuppression that is common in athletes.⁸

In addition to providing amino acids that are useful in sports nutrition, proteins are also being researched for their application in other realms of human nutrition. Whey protein, for example, may have some additional health benefits. "As a part of the nutrition industry, we [Inovatech] want to let people know that there are more benefits to whey than just building muscle," said Marcela Cota-Rivas, technical and nutritional development manager for Bellingham, Wash.-based Inovatech's nutrition division. "There is some research about whey proteins having antioxidant activity because of the lactoferrin fraction. Some experiments have suggested they even have benefits on blood cholesterol levels, and they also have immune stimulating properties."

One in vitro study demonstrated the antioxidant activity of a whey protein isolate,⁹ and another conducted with a line of human prostate cells indicated treatment with whey protein increased synthesis of the antioxidant glutathione and protected against oxidant-induced cell death.¹⁰ A human trial garnered similar results, with volunteers taking whey proteins exhibiting a persistent increase in plasma glutathione levels.¹¹

In terms of heart health, one study indicated men consuming a fermented milk that contained a whey protein concentrate exhibited lower triglycerides and improved HDL cholesterol, as well as lower systolic blood pressure than the control group.¹²

As for immune function, whey protein concentrate was studied in an animal model and shown to stimulate humoral immune responses to a range of antigens, demonstrated through enhanced serum antibody levels.¹³

One of the reasons whey protein may be useful for protecting immune function is the different fractions it contains. "It's important to understand casein is the predominant protein in cow's milk while whey is the predominant protein in human milk," said Jim Klein, vice president of sales and technical services for Erie, Ill.-based Erie Foods. "Whey protein fractions found in mother's milk, such as lactoferrin (lgG), lactoperoxidase and beta-lactoglobulin (BLG) have been shown to strengthen and protect the immune system. Studies have also shown that whey proteins positively impact digestive disorders and hypertension."

Soy is also known for several health benefits beyond performance nutrition. "When you compare the different proteins that are available, the nice thing about soy is that it gives you some additional benefits that milk doesn't give you," Jenks said, "such as lowering cholesterol, improving bone health and antioxidant status, and helping to enhance insulin sensitivity."

Research has supported each of these claims. Soy protein intake is thought to lower blood pressure and reduce the risk of cardiovascular disease,¹⁴ as well as lower plasma triglyceride levels¹⁵ and improve plasma lipids by reducing LDL oxidation.¹⁶ In terms of bone health, soy may positively influence bone and calcium levels in postmenopausal women, especially those not on hormone replacement therapy.^17,18 However, soy may not have the same protective effects on bone mineral content and bone mineral density in young women with normal menses.¹⁹

According to a research review out of a U.S. Department of Agriculture (USDA) Phytonutrients Laboratory in Beltsville, Md., soy protein was shown to reduce serum insulin and insulin resistance in animal models of obesity and diabetes.²⁰ The same review indicated that in human models, it seemed to moderate hyperglycemia and reduce body weight, hyperlipidemia and hyperinsulinemia. The researchers concluded soy protein appears to act through various mechanisms, one being antioxidant actions.

"We recommend balancing out--having a number of proteins in the diet rather than just one," Jenks said. "Although soy protein happens to be easier on kidney function and enhances kidney health, which is another reason for people who are consuming large amounts of protein to use soy."

One controversial aspect of soy is its potential effects on men's health. Some male bodybuilders and athletes avoid soy protein because of its phytoestrogen content and a fear the isoflavones may reduce testosterone levels. While not all soy proteins on the market contain isoflavones, there is somewhat of a stigma surrounding soy protein for men because of the plant's popularity in the realm of menopause relief.

The idea that soy protein will somehow reduce testosterone levels or affect men's hormone levels is "a myth," according to Jenks. She cited studies conducted in the late '80s and early '90s involving Olympic athletes when men took 1 g/kg/d to 2 g/kg/d of soy protein in addition to 1 g/kg/d to 2 g/kg/d of additional protein. The men's hormone and liver enzyme levels, as well as kidney function, reportedly were within normal ranges. "Of all the studies that have been done looking at the consumption of soy in men, there is no body of knowledge that shows any changes in sex hormone levels--they all stay within normal ranges," Jenks said.

However, soy consumption during pregnancy may affect male sexual development, according to an animal study published in April.²¹ Female rats fed a diet high in soy isoflavones, particularly genistein, gave birth to male offspring with sexual development problems. Researchers from the Johns Hopkins School of Medicine in Baltimore noted the rats born to soy-fed mothers exhibited smaller testes, long-term dysfunctional mating behavior and lower testosterone concentrations than males born to soy-free mothers.

Jenks noted that if soy consumption caused these types of problems in animals, it would not be used to feed animals used in animal husbandry, nor would scientists commonly feed laboratory animals soy-based diets. Jenks also stated there is a history of soy consumption in Asia for more than 2,000 years, and there has been no widespread report of sexual development issues in that region of the world. In addition, Jenks cited the use of soy infant formulas has been fairly prevalent over the past 35 years, with reports of normal growth and development in soy-fed infants.

Casein and caseinates (casein protein further processed for functionality requirements) have not been as popular as whey and soy proteins, likely due to a dearth of research on its benefits, although their popularity is increasing. "No commercial quantities of casein have been made in the United States since 1949 when the government eliminated subsidy support on casein while maintaining support for other dairy products," Klein said. "Consequently, there is more research being conducted on whey proteins in the United States than that of the casein protein family. But there has no doubt been a shift, generally, in how the market perceives whey protein versus vegetable and other dairy proteins. Erie Foods, though, continues to experience strong growth across the board for whey products and caseins and caseinates."

Manufacturing Considerations

Due to various manufacturing techniques, not all proteins are ideal for all applications, although ingredient suppliers and manufacturers have been stepping up research in the realm of protein technology, working to eradicate some of the more pesky processing dilemmas to make using proteins easier. Some companies have developed heat-stable whey proteins. Others have removed the isoflavones from their soy protein to reduce the bitter notes, although techniques for preserving isoflavone content while still reducing bitter notes have also been introduced in the market.

To select the appropriate protein for a functional food or beverage protein, a manufacturer should work closely with the supplier. They should also consider issues such as functionality, nutritional value, cost structure and target market to choose a protein ideally suited for the desired end product.

"After considering what your target market is, choosing a protein formulation would depend on a lot of factors, including the pH of the product and the percentage of protein desired," Rittmanic said. "If there is no restriction on the choice of proteins, a manufacturer would probably want to try several to compare cost, shelf-life, and taste and flavor aspects."

The pH is important, particularly in beverage applications, because not all proteins function well in acidic environments. "In a beverage application, whey proteins are going to function best in an acidic beverage, and soy proteins are going to function best in a neutral pH environment," Rittmanic said.

Like soy, casein and caseinates are also difficult to use in acidic applications, and they may not be as easy to use in beverages as other proteins. "Caseinates are not as soluble [as whey proteins], if at all soluble, in acidic applications without major formulation modification," Klein said.

While whey is stable in an acidic environment, it does not often hold up as well as casein, caseinates or soy under heating processes. "Whey is fully soluble in an acid medium, such as a fruit juice or a carbonated drink," Klein said. "If you use whey proteins in a liquid drink that is heat-processed to make it shelf-stable, the whey will become denatured, causing it to settle to the bottom of the drink."

Turpin added, "Customers obviously want something that doesn't sediment on the bottom of the bottle. Functional whey proteins will not withstand a very harsh heat treatment, but there have been a lot of improvements on whey protein technologies, which allows manufacturers to offer some whey proteins that are heat stable. That is particularly important for ready-to-drink [RTD], whey-based acid drinks."

Inovatech also manufactures a heat-stable whey protein that can withstand pasteurization and UHT. "For RTD beverages, you would need a heat-stable whey," Cota-Rivas said. "The difference with [Inovatech's] heat-stable whey is that it will withstand temperatures of pasteurization and UHT at low pH's. It won't gel or turn viscous, and it will be a clear liquid in solution, not cloudy or milky. Inovatech manufactures an ultra-filtered, micro-filtered, heat-stable whey protein isolate."

Settling can sometimes be an issue with soy protein as well, depending on how it is manufactured and processed. "The biggest benefit of Protient's soy protein is the solubility," Rittmanic said. "It is particularly useful for RTD beverages where you don't want any settling to the bottom of the container. Like whey, soy will also gel if it's heated, but at a higher temperature than whey. It's a little more thermally stable."

In terms of stability, Solae soy proteins are effective in high- and low-acid environments, RTD applications and dry-blended beverages. "A lot of proteins in a high-acid beverage or food are not very stable in the pH range that's required," said John Brown, director of technical services at the Solae Co. "We have proteins that are designed to be very functional in a high-acid system, meaning the solubility characteristic at a low pH of a fruit or vegetable juice are such that you can maintain a stable suspension."

While maintaining stability of a RTD beverage is important, the trend is moving toward thicker texture, according to Turpin, who also noted milk proteins are ideal for this type of application. Milk proteins are a combination of casein and whey proteins that are either manufactured to coexist or are mixed by a supplier. "A lot of people are actually interested in a very milky drink mix with a degree of thickness so their body has a sensation that it is ingesting a food-related product," Turpin said. "We're finding we have a very good response with our milk protein products on that [front]."

In addition to the popularity of RTD protein products, nutritional bars are still heavy hitters in the nutrition industry, with new flavors, textures and target market products being introduced at a constant pace. The trend with bars is to pack as much protein as possible into them, making it necessary for formulators to choose between protein concentrates and more expensive isolates.

While they are packed with protein and very little else, isolates have not been the predominant protein sources on the market for a couple of reasons. "Isolates have only really been widely available for a decade or so, and I would say that's the primary reason manufacturers have been using concentrates," Rittmanic said. "Also, they are definitely more expensive, and not necessarily as easy to work with in terms of getting them mixed into a product. Solubility, wetability, mixability--there are a lot of related issues that come into play with isolates."

However, isolates are more ideally suited to certain applications than concentrates because they are 90-percent protein and higher, leaving very little room for carbohydrate or fat content. "If a manufacturer is trying to create a low-carb, low-fat or sugar-free product for application in the sports, diet or special nutritional markets, they are going to want to choose the isolates," Rittmanic said. "If you use an isolate, you're pretty much just adding protein and small amounts of minerals. You have a lot more flexibility in formulating the other components, where you're less flexible if you use a less concentrated protein source."

Isolates are also particularly useful for very high-protein applications because they consist of 90-percent or more straight protein. "For the high-protein bars, formulators are always bound to using the 90-percent because that is the only way they can get that much protein content in the bar," Cota-Rivas said.

Many manufacturers are of the opinion the more protein, the better. "Both the nutritional bar and drink formulators have been aiming in the same direction over the last few years--maximizing the number of grams of protein you can get into each serving," Klein said. "There comes a point, though, where it becomes difficult to put that much functional protein in these applications. For now, manufacturers are really pushing that envelope."

Protein content is something many bar consumers check out, and adding the protein to a bar application--while not as tricky as adding it to a beverage application--does require certain manufacturing considerations in terms of functionality.

Whey proteins, for example, are known to be good binding agents. Similarly, caseinates are good emulsifiers and fat binders, and can offer a range of viscosity and opacity. "Casein itself is non-functional, or has very little functionality," Turpin said. "Somebody making a drink mix would definitely be looking for a caseinate because it is soluble, whereas a bar manufacturer would look for a protein source that does not impart too much texture to the bar so that it ages well. We're seeing more bar manufacturers using casein because it offers less functionality."

Soy protein can also improve the way a bar ages. In a bar, soy can control water migration, which affects how the texture of the bar fares over the duration of its shelf-life. "Bars are very popular," Brown noted. "But the big issue with protein bars is they tend to get very hard over their shelf-life. One of the functional attributes we have developed is a system to maintain a soft, palatable bar that will not harden over its entire shelf-life."

In addition to physical characteristics, flavor characteristics are a concern in the realm of functional foods and beverages. One protein said to be easily incorporated into food and beverage applications is whey protein. "One key thing about whey is that it has a very bland flavor compared to other proteins," Cota-Rivas said. "Sometimes, for example, soy will give you a chalky or even a bitter flavor. With whey, it's bland so you can combine it with any flavor, and it won't add to that flavor."

Some soy proteins deliver off-notes that require flavor-masking technology. Specifically, soy's isoflavones are considered to impart bitter notes, while soy as a whole has commonly been linked with "beany" or "grassy" notes.

To reduce the bitter notes (as well as reduce or eliminate phytoestrogen content), some companies such as Protient simply remove the isoflavones during manufacturing. "The way we manufacture our soy proteins, there are actually about 90-percent fewer phytoestrogens in our product because they simply get filtered out during the purification process," Rittmanic said. "They also contribute to the bitter flavor of soy protein, so that's one reason ours tastes better. There is a market difference in that respect, so we think it's more useful for applications such as infant formula."

There is also technology available on the market that maintains the phytoestrogen content of soy protein while removing the flavor concern. "Historically, [soy's flavor] has been a very severe issue, especially in the North American food market," Brown said. Solae has patented technology to take the off-notes out of its soy protein to deliver a very bland protein, according to Brown.

"Soy isolates don't have a 'beany' flavor, and actually have very little flavor," Jenks added. "So [a manufacturer] can use soy protein without affecting other flavors, which is good, especially in the North American market."

While proteins are linked with several flavor and physical manufacturing difficulties, mixing proteins tends to compound these issues. However, mixing proteins is popular in various market segments, particularly performance nutrition.

In the case of casein and whey, suppliers used to consistently separate the two milk proteins and then remix them when customers requested it. Mixing these proteins is still common, although suppliers have developed technologies to extract both proteins from milk simultaneously to keep them together. "There are a number of processes available that allow the dairy manufacturer to get casein and whey fractions to come out together," Klein said. One such product is an 80-percent protein milk protein concentrate (MPC) known as MPC-80, which Erie supplies from its Australian partner, MG Nutritionals. "While more formulators are using these combined proteins, many companies have developed formulations, proprietary blends, that include caseinates, whey protein isolates or concentrates in combination," Klein said.

Combining proteins brings up a list of new manufacturing dilemmas, which are slowly being fixed by companies that have poured money into R&D. "By no means can [whey and casein] not be used in conjunction with one another, but combining them certainly requires some good, close research work on these different types of proteins and understanding their limitations," Klein said. "Little by little, I see more folks going with ingredients that are as close to the original milk as possible. I think more manufacturers would like to make it simpler and use [MPCs] instead of having to work with multiple individual products that can complicate a formulation. The history over the last few years is that everybody is trying to put a little of each protein in a formulation."

A concern that comes into play with milk proteins, whey and casein is lactose content. Caseins and caseinates contain much less lactose than whey and milk proteins. "For someone who is looking for zero lactose content, casein or caseinate products are the best," Turpin said. "Second best would be a whey protein isolate, and there I would interject a word of caution. A lot of people determine they're lactose intolerant, but actually may be more intolerant to a whey protein called beta-lactoglobulin, which is a pretty large molecule predominant in most whey proteins. Whey protein isolates usually have less than .5-percent lactose, but they're loaded in beta-lactoglobulin."

Rittmanic added, "Most of the market for high-protein materials [such as whey isolates] is because the manufacturer doesn't want the lactose, which makes up the rest of the percentage, or fat. For soy, it tends to be some of the undesirable carbohydrates, which can cause digestive problems."

Going to Market

With all of the health benefits and the endless food and beverage applications, protein ingredients are being used more often and are branching out into new realms of human nutrition. Some of the always-popular categories for protein enhancement include weight management and performance nutrition, and an up-and-coming category is children's health. "There has been a lot more interest in child nutrition," Jenks said. "We're getting a lot of inquiries for the use of soy in beverages and bars for kids, healthy snacks for children."

Brown added that proteins will be popular in children's pudding-type snacks and cereal snacks, as well as beverages targeted to children, such as juices. "We're seeing a big growth in that whole market segment for soy protein as an ingredient," he said.

Soy, in particular, remains popular as an ingredient in products targeted for anti-cancer, heart health, bone preservation and women's health, according to Jenks. Another new application for soy protein is in acidic juices, such as the V8 Splash, which recently went to market with 3 g of Solae soy protein per serving.

Casein and caseinates are catching up to whey and soy in terms of popularity, according to Turpin, particularly in the realm of performance nutrition and bodybuilding. "Casein and caseinates used to be pretty big in the industry, and then whey proteins were the next Holy Grail, so to speak," he said. "Now, we're finding the pendulum swinging back toward more of a median approach. In light of the latest publications on milk proteins and caseins, we're finding people have a more balanced view of those proteins, as well. ... The trend out there is to see more science-based products for more mainstream-type applications."

With proponents of the Atkins diet increasing in number, seemingly by the minute, protein applications are also growing quickly to address the country's rise in obesity and diabetes. The mainstream public is becoming increasingly overweight--with the Centers for Disease Control and Prevention recently reporting America's obesity rate has increased to 64.5 percent of adults age 20 and older. "From talking with some mainstream, branded companies, more and more products are being enhanced with additional protein, and it's not just because of the protein, per se, but it's because of some of the work that's been done to actually make proteins function in a product where they can displace some of the carbohydrates, especially the sugars," Rittmanic said. "I think we're going to see a lot more products like protein snack chips and protein confections coming out."

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