As cave paintings by early hunters attest, even prehistoric man recognized the power of protein. He may not have known that the meat he caught supplied him with protein, but he knew that without it, he would weaken and eventually die.
Protein is essential to life, but all proteins are not equal. Protein is made up of strings of amino acids, some of which are essential. Histidine, isoleucine, leucine, lycine, methionine and cystine, phenalalynine and tyrosine, threonine, tryptophan and valine all must be present for the protein to be considered complete. The Protein Digestibility-Corrected Amino Acid Scoring (PDCAAS) method measures the amino acid profile of a protein, taking into account the protein’s digestibility and the presence of essential amino acids in the amounts required by humans. Complete proteins, such as egg, milk and soy, have PDCAAS scores of 1.0.
While proteins are valued for their nutritional strengths, they are also prized for the functionality they bring to food systems. Depending on the type of protein and its complex chemical structure, it may excel at binding water or fat, at forming foams or gels, or at emulsifying.
Protein isolates, which contain 80% to 90% protein, provide the food developer with the most concentrated form of protein. Following is a look at some of the available choices.
Ways with wheatWhen developing flour-based foods such as breads, rolls, pasta or snack foods, consider adding wheat protein isolate, which contains 85% to 90% protein. “Wheat protein isolates are unique to soy or dairy proteins in that they offer vitality, or the ability to form a dough upon rehydration,” says Steve Ham, director of marketing, specialty ingredients, MGP Ingredients, Atchison, KS. “Wheat protein isolates are effective in adding strength by supplementing protein present in flour, as well as increasing volume through gas retention due to film-forming properties.”
All proteins have an isoelectric point, the pH in which they have an equal number of positive and negative charges and are least soluble. “Wheat proteins have an isoelectric point at a neutral pH of around 6.5,” says Ody Maningat, corporate director of R&D and technical services, MGP Ingredients. “As you move away from a neutral pH, either higher or lower, a wheat protein isolate will show more solubility.”
For formulating, a protein’s isoelectric point can have many consequences. Wheat proteins provide their most strength or elasticity at or near their isoelectric point. Extensibility and elasticity are important attributes for different bakery applications. Elasticity increases as the isoelectric point is neared; however, in the neutral pH range, the protein is still extensible.
The several types of wheat protein isolates differ primarily in their extensibility and elasticity properties. “When you look at a wheat protein isolate with a pH away from neutral, it tends to have more of the extensible properties and less of the elastic properties,” says Maningat.
Whole-grain applications illustrate the importance of these attributes. “Where you have a lot of particulates in the dough, you might lean toward an elastic-type protein to get the greatest amount of strength,” Ham says. “In very delicate baked goods, like a muffin or cookie, where you might want to add some proteins, a more extensible protein should be used to maintain tenderness. Added extensibility can help in sheeted or pressed-dough products such as pizza crust or tortillas by reducing the retraction of the dough and by aiding in pliability.” This also extends shelf life.
High-protein wheat products, which made a splash during the low-carb craze, posed challenges to bakery scientists. “The high level of wheat protein tended to be difficult to process,” says Maningat. “The addition of wheat protein isolate to the formula balances the ratio of elasticity and extensibility. It makes it possible for that high-protein bakery product to be processed in a conventional bakery plant.”
Ham recommends using 0.5% to 1.5% wheat protein isolate in bread and roll applications to help reduce mix time, add extensibility and improve dough-handling properties. “Wheat protein isolate helps to retain gas, which results in increased volume,” he says.
In pasta and noodles, wheat protein isolate can replace egg whites while retaining firmness. “Usage levels are dependent on the process,” explains Ham. “It can range from 1% for supplementing semolina or flour in dry or fresh noodles, to a use level of 4% to 6% in retorted applications.”
Wheat protein isolates also add value to predust and batter systems. “The film-forming properties of wheat protein isolates aid moisture retention, which translates to increased yields and cost savings while maintaining desirable sensory properties,” says Ham.
Nutritionally, wheat protein isolates have a lower PDCAAS score (0.25) than several other botanical or animal sources, as its composition is lower in the amino acid lysine, so it may not be the first protein that comes to mind when formulating nutritional drinks. However, wheat proteins are rich in glutamine, a nonessential amino acid. “Glutamine helps the body recover from stress and fatigue due to overexertion from activities such as weightlifting or surgery,” says Ham.
Soy goodWhile wheat has unique functional properties that cannot be mimicked by other proteins, soy protein offers similar functionality to milk and meat proteins in many applications, notes Russ Egbert, Ph.D., director of protein research, ADM, Decatur, IL. “In many cases, we can replace milk and meat proteins with soy proteins that have similar functional properties, such as emulsification characteristics or solubility characteristics, and typically at a cost advantage,” he says. “In some cases, depending on the application and if soy is used for a functional benefit, you can actually use less.”
Many proteins can provide emulsification. “Fat is hydrophobic,” Egbert explains. “When forming an emulsion you are trying to align the hydrophobic portions of the protein with the fat so they can interact.” By comparison, a phospholipid has a highly charged, hydrophilic polar end and a long hydrophobic tail. “When you look at the pure emulsions, those tails penetrate into the fat or the oil droplet, and the polar heads are on the outside interacting with water,” says Ebert. “It does not matter whether the protein is an isolated soy protein or milk protein as long as it is soluble. You are basically looking at interacting fat with that protein in a hydrophobic level.”
Water binding is another attribute of soy protein. This can be beneficial in replacing lean-meat protein. “Soy proteins can have gelation characteristics. You can actually achieve similar gelling characteristics with soy protein that you would with the meat proteins. This is not something you would necessarily get with the other proteins,” Egbert says. Protein levels of isolated soy protein isolates are about 90% on a dry basis. “On an asis basis they range around 86% to 88%,” he continues. “In a marinated meat product you might be using as little as 1%. If you are producing product for school lunch, like a chicken patty, you might use up to 5% of isolated soy protein. The isolated soy protein would be hydrated to 18% protein content with water and used to replace meat.”
In dairy applications, soy can replace milk protein, either fully or partially. “If you have a dairy yogurt that has 10 grams of milk protein, you can produce a soy-based yogurt product that has 10 grams of soy protein,” Egbert says.
Nutritionally, soy protein has a full complement of amino acids and is considered nutritionally equivalent to egg, milk and fish. “With a perfect PDCAAS of 1.0, isolated soy protein contains all nine essential amino acids.” says Christopher Cairo, senior manager, market development, The Scoular Company, Omaha, NE.
The major applications for soy protein isolate in the domestic market are in nutritional products. “We have been successful in introducing our soy isolate into nutritional/protein bars, protein crisps, meal replacement and bakery applications,” Cairo says. “Today’s consumer is better educated and focused on nutrition, with a large percentage of consumers considering soy products as healthy. As this trend continues, we believe soy protein will play an important role in providing the foods and beverages that consumers will be demanding.”
While the flavor of soy protein has improved over the years, there are still some flavors associated with soy that are unique, Egbert cautions. “Each protein, regardless of whether it is milk, soy, wheat or meat, has a unique flavor associated with it,” he says. “In some cases, masking agents are used in product development with soy, but, generally, flavorists today are very good at producing flavors that work well with soy.
“When I started working with soy 15 years ago, a lot of the flavors we could source had been developed for use with dairy proteins,” Egbert continues. “Proteins bind up flavor. There are many components that make up any flavor, and if you use a flavor developed for use with dairy proteins in a soy-based product, the soy may bind up certain compounds critical to flavor delivery. For example, a strawberry flavor developed for dairy may be lacking various key flavor notes characteristic of strawberry when used in a soy-based product. In this case, the soy protein has probably absorbed certain key compounds that are critical to the flavor delivery.” He notes that when developing a flavored product, whether it’s a nutritional bar, a beverage or a bakery product, product designers need to remember to source flavors that complement one another.
Aside from flavor, it’s important to select the right protein for product development work. When choosing a soy protein isolate, it is best to work with the technical staff of your soy supplier, Egbert advises. “It is important that the supplier understand what you are trying to achieve in your product development efforts,” he says. He points out that his company has “over 25 different isolated soy protein isolates with very unique and different functional characteristics,” so the right one will depend of the functionalities and end result needed for a specific application.
In any aqueous-based product application, such as an RTD beverage, it is important to ensure that the protein is properly hydrated. “There are key methods used to hydrate protein, in order to achieve the greatest product functionality and stability,” says Egbert. “We recommend that the protein be hydrated in 40°C to 50°C water for a minimum of 10 minutes. Typically, a high-shear mixer is used to initially disperse the protein into the water, after which the mixer speed should be reduced to minimize the incorporation of air into the mixture. Air entrapment will cause foaming and result in difficulties with homogenization and packaging later in the process.”
Once the protein is properly hydrated, other critical factors are needed to achieve maximum product quality and stability. “There are a variety of gum systems that are used to stabilize beverage product, depending on the final pH of the beverage,” says Egbert. “Again, understand your application. The appropriate stabilizers for use in that system are critical to your success. One last key parameter in your beverage development efforts with soy protein is homogenization. Proper homogenization is essential in the development and manufacture of stable beverage products.”
Yolk and allEgg protein has long been prized for its functional characteristics. Egg yolks provide emulsifying properties. Egg whites excel at binding and foaming. Nutritionally, eggs are a complete protein with a PDCAAS score of 1.0.
Dried egg whites are virtually all protein to start with, explains Karen Moss, food scientist, Henningsen Foods, Omaha, NE. “There is no isolation step to remove fat or carbohydrates as in soy or whey isolates,” she says. Henningsen’s new EP-2 egg white peptides contain greater than 90% protein. “The main nutritional benefit of egg white peptides is fast and easy digestion, enabling the amino acids to reach muscles quicker for accelerated recovery following exertion,” she continues. “Egg white protein is a complete protein, since it has no limiting essential amino acids. Also, egg whites contain higher levels of sulfur amino acids than both whey and soy. Sulfur amino acids are required for protein synthesis, collagen formation and maintenance of joint health.”
Sulfur amino acids contribute a distinct flavor. “The egg white peptides currently available have a strong bitter taste and are very limited in usage,” Moss continues. Henningsen’s product has a mild bland flavor. “The flavor enables it to be used in a wide range of products requiring protein fortification,” she says. “It was designed with nutrition bars and protein drinks in mind, but it does not need to be limited to those categories.”
Henningsen’s egg white peptide product is a low dusting, free-flowing powder made by processing liquid egg whites using a controlled enzyme hydrolysis then spray-drying into a powder. “The peptides produced during the hydrolysis process enable the body to rapidly digest EP-2 and put the amino acids to work quicker than the intact proteins found in soy and whey isolates,” Moss says. “Egg white peptides are a good choice for the diet of aging populations, which may have trouble digesting many common sources of protein, leading to deficiencies. Incorporating egg white peptides in product will help deliver the amino acids required for optimum health.”
Just add milkMilk protein isolates (MPI) are produced by ultrafiltration of fluid milk. “To concentrate to 90% protein on a dry solids basis, an additional diafiltration step is usually involved,” explains Sharon Gerdes, technical support consultant for Dairy Management Inc.™ (DMI), Chicago. “Milk protein is composed of roughly 80% casein and 20% whey protein.”
Milk protein isolates are ideally suited for a variety of nutritional beverages, because they are soluble in water and contribute a clean dairy flavor. “They have good heat stability and emulsification properties and work well in retorted beverages,” Gerdes says.
In beverage applications, MPIs work best in a neutral pH. “The isoelectric point of milk is 4.6,” Gerdes says. “At that pH, caseins precipitate. Milk protein isolates are usually used in beverages above that pH level. These beverages are typically more opaque.”
According to Gerdes, milk protein isolates are also used in nondairy creamers, margarine, imitation cheese, bakery, confection and meat. “With their superior emulsification properties, milk protein isolates work well in whipped products,” she says.
Two methods are used to manufacture whey protein isolates (WPI), explains Dennis Vosen, technical director, Century Foods International, Sparta, WI. “One is by filtration and the other is by ion exchange,” he says. “The filtration technique produces about an 80% whey protein concentrate, then that material is subjected to micro-filtration, which concentrates the remaining lipids in the product and allows the proteins to pass through the membrane.”
In the ion-exchange method of manufacturing WPI, the proteins in fresh skimmed sweet whey are exchanged with sodium ions on a resin bed, then the bed is regenerated by introducing a strong salt solution, thereby removing the proteins. The resulting solution is evaporated and spray-dried. “Whey protein isolates manufactured by this method do not contain all the proteins in the original whey and have a different mineral profile than their membrane processed counterparts,” says Vosen.
Microfiltrated WPI contains 0.492% calcium, 0.059% magnesium, 0.592% potassium, 0.242% phosphorous and 0.228% sodium. Ion exchange manufactured WPI contains 0.081% calcium, 0.010% magnesium, 0.080% potassium, 0.025% phosphorous and 0.467% sodium.
Microfiltrated WPI contains 14.9% alpha-lactalbumin, 55.7% beta-lactoglobulin, 2.5% immunoglobulins and 20.6% glycomacropeptide. In comparison, ionexchange manufactured WPI contains 25.6% alpha-lactalbumin, 66.0% beta-lactoglobulin, 2.5% immunoglobulins and 0% glycomacropeptide.
According to Gerdes, alpha-lactalbumin is one of the most nutritious proteins available. “When it is added to infant formula it produces an amino acid profile similar to breast milk,” she says. “Alpha-lactalbumin is also a major source of tryptophan and has been shown to stimulate serotonin and melatonin synthesis and improve sleep.”
Beta-lactoglobulin is responsible for most of whey’s functional properties, such as gelation and water binding. Whey proteins contain the highest concentration of branched-chain amino acids (BCAA) of any protein source. “BCAAs are important in muscle metabolism and can be used as a source of fuel during endurance exercise,” Gerdes says.
“The advantages of whey protein are pertinent to athletes to whom protein may serve as a large source of energy,” says Gwen Bargetzi, director of marketing, Hilmar Ingredients, Hilmar, CA. “Much of this energy is thought to come primarily from BCAAs—leucine, isoleucine and valine. BCAAs—metabolized by muscle, not the liver— are unique among amino acids in their ability to provide a ready and direct energy source to muscle during exercise. During exercise, the body’s demand for BCAAs increases and adequate dietary supply is needed to prevent muscle catabolism.” She notes that RTD and drymix beverages are common vehicles for protein supplementation.
Vosen notes that BCAAs are soluble at the pH of the digestive tract and “increase blood amino levels in a much shorter period of time after ingestion, compared to other protein sources which must be ‘predigested’ to first make them soluble,” he says.
“Whey proteins 90% and greater, such as isolates, are especially suited to nutritional uses because they provide pure, high-quality protein with little or no fat and lactose,” says Bargetzi. “Higher protein—80%- plus—whey proteins have superior protein quality, excellent digestibility and the right balance of essential and nonessential amino acids for optimal nutrition.” She notes that the betalactoglobulin, alpha-lactalbumin, bovine serum albumin, immunoglobulins and the minor proteins, including lactoferrin and lactoperoxidase, in whey protein can all make unique contributions to human health and athletic performance.
“Hydrolyzed whey protein isolates can provide free amino acids and peptides for quicker absorption in sport-nutrition products such as bars and beverages,” says Grace Harris, manager of applications and new business development, Hilmar Ingredients. “Hydrolysates can also provide specific functional benefits in RTD beverages—heat stability— and bars—shelf-life extension.”
The isoelectric point of whey proteins varies. “Beta-globulin’s isoelectric point is 5.3 to 5.5 pH,” says Gerdes. “For alpha-lactabumin it is 4.2 to 4.5. If whey protein isolates are used in a beverage where the pH is closer to the isoelectric point, say 3.5 to 4.5 pH, the beverage will be more creamy in appearance. If a food formulator wants to develop a clear beverage, they should bring the pH down to about 2.8 to 3.4. Adequate hydration time (10 to 20 minutes) will increase beverage clarity.”
Different applications dictate different WPIs. “Choosing an optimal level of whey protein incorporation will ultimately depend on the overall nutritional target, other ingredients in the formula and processing steps,” says Harris. “Choosing the correct WPI for functionality, as well as flavor and protein load, is important.” For example, she notes that product designers could use a WPI with good acid and/or heat stability at high concentration in an RTD beverage to retain low viscosity and clarity.
Simon Leitch, business manager, Fonterra Co-operative Group, Auckland, New Zealand, says one should consider using an acidic WPI for certain applications. “While we have a range of WPIs, our acidic WPI is ideal for sports nutritional products where consumers want a large dosage of protein that still tastes good,” he says. “Protein typically does have an impact on flavor. We have tried to minimize that as much as possible, in order to provide as bland a base as possible.” The product is produced by microfiltration and ultrafiltration.
The acidic WPI has a typical pH of 3.3 at 5%—the isoelectric point in acid whey does not change, as it’s a property of the proteins. “We’ve developed an acidified WPI in recognition that a lot of nutritional products are acidic.” says Leitch. “At a lower pH you have much greater flavor versatility with the likes of citrus and tropical flavors, whereas at neutral pH, you are limited to neutral flavors like chocolate, vanilla and strawberry.
If you use a neutral WPI, you have to add acid into the system to get to that lower pH. “The protein acts as a buffer and you can end up throwing a lot of acid into the system just to get to the desired pH,” Leitch continues. “We’ve tried to alleviate that to some degree. That means that you don’t have to add so much acid to the system, which has the advantage of reducing sourness and astringency.”
In product formulation, Leitch recommends usage levels from 1% to 7% protein content. “When you are at 7% protein you are really talking about a product that is intended for serious sports people, particularly bodybuilders,” he says. “For bar and bakery applications I’d recommend one of our neutral WPI or whey-crisp ingredients.”
Functional characteristics of whey protein isolates make them ideal for applications where thickening and water-binding is important. “They exhibit heat-induced gelation,” says Gerdes.
The gel-forming characteristics of WPI manufactured by ion-exchange technology can be manipulated by controlling the ionic conditions of the solution. “For instance, in solution, it can be heated above the denaturation point of all the proteins at a high solids concentration and still remain fluid and unaggregated,” says Vosen. “If a calcium source is then introduced, a clear, firm, irreversible gel forms.” This characteristic gives it an advantage in comminuted food products like surimi and processed meats. Whey protein isolates are finding new applications. Gerdes says one of the newer products using WPI is Quaker Instant Weight Control Oatmeal. “This product contains 7 grams of protein per 45 gram serving,” she says. “Oats contribute part of the protein. Newer research has shown that whey protein can help to build and maintain muscle mass, which is an important component of weight management.”
Leitch sees some unique opportunities for whey protein isolates in the United States. “We have been developing two new formats: jelly drinks and protein shots,” he says. “Jelly drinks are a well-established beverage category in Japan but new to western markets. In Japan, jelly drinks contain a broad range of ingredients, including protein, and are sold through convenience stores, supermarkets and pharmacies. We’re excited about this product format because it is a great carrier for protein. Protein shots are a line extension from the carbohydrate shot or gel concept, which are popular with people who undertake prolonged exercise.”
New introductionsAlthough most product designers are familiar with dairy, egg, soy, wheat and whey proteins, other options exist. One such new form of protein, brown-rice protein concentrate, is derived from sprouted brown rice. In brown rice, the protein is distributed between the bran and endosperm layer, and makes up approximately 7% to 9% of the grain. The beige-colored product, Oryzatein™ marketed by Axiom Foods, Inc., Los Angeles, is hypoallergenic, has a sweet, bland taste, and is rich in essential and nonessential amino acids. According to David Janow, president and CEO, the protein quality of brown rice protein was assessed for PDCAAS and biological value (BV) using growing rats, scoring values of 1.00 PDCAAS and about 98% BV. “Even the limiting amino acid, lysine, is 366% greater than the recommended level,” he says. “Plus, because the flavor is very bland to slightly sweet, you don’t need to mask it.”
The protein level is approximately 85%; 90% is achievable, but currently not cost-effective. The product stays suspended in liquid without leaving a gritty mouthfeel. Janow recommends applications similar to other protein powders: powdered drink mixes, bars and chocolate-type coatings and chips. He notes current research on a product for the meat industry and advises: “Remember, not every protein has the same effect on gelling and emulsification. In the early days, soy and other proteins didn’t have much variation in functionality,” but as the product takes hold in the market, similar modifications are possible.
In the future, product designers may be able to add canola protein to the mix. Burcon NutraScience Corporation, Vancouver, British Columbia, has developed an extraction process and entered into a licensing and development agreement with ADM, Decatur, IL, to commercialize canola protein ingredients. Burcon can extract the protein in the isolate range (plus-90%), with the resulting ingredient possessing a bland, slightly grainy flavor, golden color and little or no odor. However, canola protein does not yet have FDA approval for food use.
Protein-fortified oatmeal, jelly drinks and protein shots are but a small measure of how the food industry has expanded our diet options. These wouldn’t have been conceived of 75 years ago, much less 20,000 years ago.
Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached firstname.lastname@example.org.