Proteins headline the greatest show on earth: plant and dairy proteins wear numerous hats in the food formulation arena. Now that the low-carb circus is in town, protein's high wire juggling act is finally in the limelight

Prepared Foods, August, 2004 by Marcia A. Wade

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 Viscosity

In 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[degrees]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.

Clarity

Achieving 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 Bars

Plant 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."