Plant and dairy proteins provide water management, emulsification and flavor to enhance food formulations. Of late, their popularity has ballooned due to their use in dietary regimes and the rise in low-carb reformulation. “We are seeing new interest beyond what we would in our traditional avenue of protein sales,” says Steve Ham, director of marketing for specialty ingredients at a wheat protein ingredient supplier. “The diversity of products which we are helping customers formulate is getting much broader.”
Plant and dairy protein products are sold as protein concentrates and isolates, textured concentrates and fractionates, which can be derived from soy, wheat or whey (among other sources). The underlying challenge is determining how to manipulate them into the application at hand.
Solubility and ViscosityIn beverage applications, pH influences viscosity, solubility and dispersability of proteins, notes Bill Soucie, director of product development at a soy ingredient supplier. Beverages can be categorized as ready-to-drink, neutral, acidic and/or dry blended. Problems with acid stability typically arise in drinks with a pH ranging from 2.8 to 4.5, like fruit juices where most proteins are unstable due to minimum solubility.
Whey proteins are highly soluble at a lower pH, although, when heated above 70°C, some solubility can be lost due to denaturation. “For optimum solubility, use as little heat as possible,” suggests Sharon Gerdes, a technical support consultant for DMI (Rosemont, Ill.). Recently, more heat-stable whey proteins have been developed. “If you are preparing an acidic beverage, like a sports beverage or fruit-based beverage, then whey proteins are an excellent choice,” comments Gerdes. Food processors are developing ultra-high temperature (UHT) or retort beverages with an increased shelflife.
“Hydrocolloids are typically added to stabilize dairy proteins at those higher temperatures,” she opines. There are new technologies for milk proteins, in general, that are carried out under aseptic conditions, requiring less heat to maintain shelf stability. Some of these newer processes are used in dairy beverages and are approved by the FDA for extended shelflife.
Other factors decreasing protein solubility include higher concentrations of ions like calcium and sodium. Using certain stabilizers, such as carrageenan, helps keep proteins in solution. Whey proteins contribute to water binding and viscosity, due to their globular structure. Such properties inhibit syneresis in yogurts. Water binding may be desirable in yogurts, but not always in beverages. By controlling the level of denaturation, a large range of viscosity can be achieved using whey protein.
Properties such as stability and viscosity--including the rate that viscosity builds within a product--largely are determined by a protein's molecular size.
Hydrolyzed whey proteins, with shorter protein lengths, are more rapidly absorbed and also minimize allergenic properties. This property makes them popular additions to infant formulas. A process whereby whey proteins can also be formed into polymers creating larger molecules is now being commercialized. These polymers have higher viscosities, unique flow properties and the potential to replace carbohydrate-based hydrocolloids in reduced-carbohydrate beverage applications.
Whey protein isolates contain protein levels of about 90% or more with usually less than 1% lactose and fat. Whey, soy or wheat protein isolates are useful when a high protein content is desirable or if a manufacturer wants a product with very little lactose or fat content.
ClarityAchieving a clear beverage ushers in additional challenges, regardless of the protein source. Often, proteins cause aggregation and turbidity if used at high levels, says Soucie. Whey protein isolates generally have less fat. Fat increases the turbidity. “If your objective is to have higher protein content in your clear beverage, then you want to choose an isolate,” advises Gerdes.
Soy proteins can be hydrolyzed extensively and broken down into soluble pieces that provide a clear soy beverage. If the proteins are not broken down into smaller units, they reflect light, preventing a clear liquid.
Behind BarsPlant and dairy proteins are valuable in bakery applications where they help reduce cooking and baking losses, improve yield and increase moisture and water retention. “A certain amount of water is lost in baking. Water binding by proteins not only increases the yield, but also the tenderness of the product,” says Gerdes.
Extending the shelflife of nutrition bars has been an ongoing challenge. “There are three types of functionality that our customers want in bars: good flavor, good texture and long shelflife,” advises Soucie. “In this scenario, microbial instability is not a problem, but rather water migration.” One result is that high protein bars tend to be hard. In an effort to extend shelflife, some companies have developed various proteins that control migration of water molecules. “We've been able to increase shelflife up to 10 times with some of our new [soy] technologies,” comments Soucie. “Most bars are composed of a mixture of proteins.”
For example, “One protein will give you a chewy, tootsie roll-like texture and another will give you a short crumbly texture, more like a brownie.” Mixing proteins with different textural attributes to achieve intermediate characteristics is common in the nutrition bar industry.
Wheat protein isolates are easier to incorporate than wheat gluten during processing in yeast-leavened, low-carb products. This improved “machinability” is attributed to its mellow visco-elastic properties. Some wheat protein isolates are more extensible or stretchable than standard gluten, explains Ham.
Since many nutrition bars are extruded, proteins are chosen based on how they behave in an extruded system, says Soucie.
When proteins themselves are extruded, the resulting protein crisps can be added to snack foods and nutrition bars to help equilibrate moisture over time. Textured whey proteins can be manufactured into just about any shape,” explains Gerdes.
Soy crisps, or soy nuggets, are different sizes and shapes and have protein contents that generally range anywhere from 50%-80%. “These nuggets are designed to go through the extruder,” advises Soucie. “It makes the texture more interesting and less homogeneous.” These crisps or nuggets also are available in protein sources other than soy. Processors can attain even more variability by paying attention to the subtleties in density of crisps and how they interact in a bar matrix.
While extruded bars are chewy or cake-like in texture, sheet and cut bars are composed of several solid pieces. “That kind of bar is not extruded, but sheeted out and cut like a rice crispie square,” states Soucie. In this case, the protein nuggets are a larger share of the formula with other inclusions such as fruit pieces, peanuts and vegetable or texturized meat pieces, which are more common in nutrition bars overseas.
Flavor IssuesAll concentrated forms of protein have their challenges with regard to flavor, and soy is no exception. Many soy proteins have increasingly acceptable flavors, especially when blended with chocolate, vanilla and other proprietary flavoring systems. However, there are still some unresolved issues that contribute to what some describe as “beany” flavors.
Wheat proteins have the advantage of contributing to the natural wheat flavor that most baked products target. Whey can enhance certain flavors and help flavors to carry through in baked goods. And, some proteins work well in vanilla or fruit-flavored, milk-type beverage applications. “In beverages, whey's bland sweet flavor enhances fruit and chocolate flavors,” says Gerdes. “As compared to soy, whey protein isolates have a very clean flavor.”
EmulsificationProteins are typical emulsifiers. They are amphipathic, meaning they expose both their hydrophobic and hydrophilic moieties, allowing them to align at oil/water interfaces. Protein emulsions can be used in baked products, ice creams, dressings and coffee whiteners.
“Lecithinated soy proteins are excellent emulsifiers,” observes Soucie. To create lecithinated soy proteins, lecithin is mixed with the proteins, which makes them more dispersable. This is valuable in salad dressings or mayonnaise-type products. Whey proteins can be used to (at least) partially replace eggs and certain starches and gums, which create a dual use in low-carb products.
Foams are similar to emulsions, except foams stabilize the interface between two air cells. Foams, in general, benefit from the use of proteins that have not been denatured.
A Meaty SolutionPlant and dairy protein products work in meat to bind water and improve texture, yields, succulence and cooking stability. “Functionality will vary across different applications like roast beef, breakfast sausages and chicken fillets,” explains Al Gallegos, marketing, a soy protein ingredient supplier.
Proteins are available in powdered isolates, textured and functional concentrates and flours. Some companies have structured vegetable proteins that emulate whole muscle meat-like products. “Each protein platform helps re-create characteristics found in meat, poultry or pork. By combining different ingredient platforms with flavors and spices, one can develop products with the texture, flavor and appearance of a beef burger or chicken tender,” says Gallegos.
Some ingredients might perform better in a texturizing process, or they may work better in extruded applications. “If, for example, you want a hot dog with more meat-like characteristics, you may use a soy protein isolate that binds more water, giving the product a firm texture and better initial bite,” suggests Gallegos.
Recently, textured wheat proteins were launched in a pre-shredded dried form similar to fibrous shredded meat used in barbecue. These fast-hydrating fibers are designed to be processor friendly. They are added to the formula at the same time as the water, eliminating a separate hydration.
Incorporating soy protein into breadings and coatings to achieve a high-protein, low-carb breaded product highlights some of the exciting new ways that plant proteins are being used.
Wheat protein isolates also can be added to meats and meat alternatives to improve quality and deliver cost savings. In batter and breading applications, wheat protein isolates can be used in pre-dusts and batter systems applied as coatings to whole muscle and reformulated meat pieces. Adding these proteins helps the batter adhere to meat substrates. Although plant and dairy proteins can be used to replace flour to lower the carbohydrate content, the texture will change somewhat. For example, the use of wheat protein isolates in coatings may “contribute some crispness due to its film-forming and moisture barrier properties, which would be less [noticeable] if using 100% vital wheat gluten,” says Maningat.
“It is important to note that proteins are not used independently in low-carb systems. [Dietary] fiber can be used in conjunction with protein to achieve the right type of characteristics,” informs Soucie. For instance, “There is a wide array of products where wheat proteins can be very functional in conjunction with resistant wheat starch,” adds Ham. Using a resistant wheat starch with added wheat protein isolate in place of wheat flour can significantly reduce the amount of digestible carbohydrates.
Although proteins will continue to participate in the low-carb circus, their long-term use is secure due to the less flashy, but very fundamental benefits they bring to foods. “We are really not using soy protein in places where you would never see protein before,” says Soucie. “Many of the food products that we look at have proteins in them already.” Only the protein sources may have changed.
Sidebar 1: Going Global: The Wheat WithinFrom fish products to noodles and tortillas, wheat proteins can be used to enhance many international products. Kamaboko, a fish cake that is popular in Japanese households, is one example. It uses a surimi-type starting material mixed with starches, protein and other ingredients that are then molded into a cylinder or a long cube. Japanese consumers use it for a snack-type product dipped in sauce. A finished kamaboko has rubber-like properties (such as bounciness) when bitten into and chewed. When wheat protein concentrate is added, it firms the texture and provides elasticity.
The soft noodle, the Chinese noodle and the Udon (a term for Japanese salt noodles) all use proteins to enhance the firm texture and reduce stickiness. “Wheat proteins are a natural fit in wheat flour-based foods including pasta and noodles,” explains Ham.
Maningat worked recently with the shelf stability of flour tortillas by adding wheat protein to increase the number of days that the tortilla remains flexible and pliable. “In the absence of our [wheat] protein, the tortilla will only last 10 days,” informs Maningat. “We can easily double the number of days by adding 1% of our wheat protein in the tortilla formula.” Ham believes this increased shelf stability is unique to wheat proteins, as they add resistance to tearing and help retain moisture. Maningat agrees, “I haven't seen anything in the literature that supports the same phenomenon for other protein sources.”
Sidebar 2: Protein Priorities to Improve HealthThere are several examples of how plant and dairy proteins can be used to improve health. New products are emerging with nutritional parameters specific to customer's nutritional needs. Wheat protein is rich in glutamine, which is considered a conditionally essential amino acid. With the amino acid profile of wheat, a synergistic effect can be realized when used in combination with other protein sources such as soy.
Whey proteins contain higher levels of branched-chain amino acids than any other protein, making them excellent choices for popular low-carb items. Newer research shows that branched-chain amino acids, such as leucine, may play an important role in maintaining glucose homeostasis and preserving lean muscle mass in weight loss regimens.
The FDA has approved a health claim of reduced risk of heart disease in conjunction with 25g of soy protein per day, as part of a diet low in saturated fat and cholesterol. In March 2004, a petition was submitted seeking another claim, based on 58 studies supporting the relationship between the consumption of soy protein and the reduced risk of developing certain types of cancer.