Picking Out Proteins

For the product developer, proteins serve a dual purpose: functional nutrition and product functionality. Proteins are the building blocks of the human body. They carry the oxygen in our blood, they are the antibodies that keep us healthy, and they are the enzymes that start digesting food the moment its in the mouth. In addition, proteins play an important role in giving structure and stability to food. They are the emulsifiers in sauces, foaming agents in meringues, gels for confections and water binders in meat.

Building proteins 

Proteins diverse functionality comes from its structure: amino acids joined by peptide bonds. The primary structure is the sequence of the amino acids, which are differentiated by their side chains, and can be neutral or carry a positive or negative charge. The secondary and tertiary structure of the protein is the lowest energy conformation of the protein chain. For example, the secondary structure can be a helix stabilized by hydrogen bonds, and the tertiary structure would have that helix folded with the hydrophobic amino acids inside the structure. The charges on the protein, as well as the hydrophobicity and the conformation, contribute to the proteins functionality.

The isoelectric point (IEP) is the pH at which the net charge on the protein is neutral. The charges allow the protein to interact with water and repel other proteins in solution. Neutralizing the charge reduces the proteins tendency to hydrogen-bond with water and lose solubility. Proteins are least-soluble at their IEP. Salts in solution with protein also affect the charges; low levels help the solubility of proteinsalting inby masking the attractive charges on the protein molecule so it interacts more with water. High levels cause proteins to salt out, due to competition for water.

Much protein functionality comes from denaturation, which leaves the peptide bonds intact, but changes the secondary or tertiary structure. Denatured proteins have higher viscosity and lower solubility than the native form. For surface-active properties, the protein will denature to align itself at the interface. With wheat gluten, the protein denatures as a result of mechanical work and exposes cysteine residues that form disulfide bonds. No single protein works in all applications, but the right protein can be selected according to the formulation and the process.

From the field 

The health benefits of soy protein have been well-communicated. Foods with at least 6.25 grams of soy protein per serving may carry an FDA health claim relating its consumption to the reduction of heart disease. Soy protein is also a complete protein, containing all of the essential amino acids. Soy protein ingredients include soy flour, soy protein concentrate and soy protein isolate. The protein contents of those ingredients are 50%, 65% and 90%, respectively. Soy protein functionality can be optimized for different applications. Deborah Schulz, market development manager, Cargill Health & Food Technologies, Minneapolis, explains: Things such as viscosity, gelling properties, flavor, etc., can be different for different types of products. Typically, flours are more similar in these properties, while concentrates have more variety and isolates offer the greatest flexibility.

Processing impacts both functionality and flavor. For example, The reformulation of the protein molecule followed by spray-drying results in stronger emulsion and gel performance and higher water-holding capacity in cooked meat and poultry products, according to Gary Brenner, vice president marketing and sales, Solbar Industries Ltd., Ashdod, Israel.

Like other proteins, pH, salt and process temperature impact how the protein works. This can be managed by understanding how the other ingredients interact with the protein and optimizing processing. Schulz adds that high salt concentrations may be an issue, as well as the presence of divalent cations. For low-pH beverage applications, she recommends special processing and adding protein-stabilizing ingredients.

Pea protein has functionality across many product categories. Nutralys is a non-allergenic vegetable protein derived from yellow pea that offers high emulsion and gel properties, dispersibility and stability to many finished products, says Chandani Perera, project coordinator, technology and applications development, Roquette America, Inc., Keokuk, IA. A functional form of this pea protein improves product texture, and a soluble form can be used at higher levels to maximize nutritional benefit to 25% in nutrition bars, without negatively impacting texture, and up to 85% in drink mixes. Other applications include gluten replacement in cookies, bread and pasta, and as an emulsion stabilizer in sauces, dressings and mayonnaise without eggs.

Zein, a predominant protein in corn, is not soluble in water, but is in ethanol. Traditionally, zein has been used as a nut or confection coating, similar to shellac. Because natural zein does not associate with water, it does not provide functionality in foods like other proteins. At the University of Illinois at Urbana-Champaign, Munir Cheryan, Ph.D., research professor, employed enzyme modification and membrane technology to dramatically improve zeins solubility in water, opening the door to new applications.

Wheat proteins are essential to our daily bread. Gliadins and glutenins are the two proteins in the wheat endosperm that are most responsible for the formation of an elastic dough. As the flour is hydrated and kneaded, the proteins partially unfold to allow hydrophobic groups to interact with each other and allow disulfide bonds across cysteine amine groups. A correct balance of glutenin and gliadin proteins gives bread dough the elasticity and extensibility required.

Wheat proteins can provide other functionality. ADM, Decatur, IL, has developed functional wheat protein isolates that enhance the taste, texture and appearance of cereal clusters, baked products and snacks. In addition, they increase protein content without altering flavor, and reduce bitterness in whole-grain applications. They can be dissolved in water at relatively high concentrations for use as a sugar-free adhesive, and act as an economical replacement for dairy or egg proteins.

In addition to contributing functionality and nutrition, further processing of plant proteins can contribute flavor and flavor enhancement. HVP and HPP are acronyms for hydrolyzed vegetable protein and hydrolyzed plant protein, says Brian Glickley, marketing manager, Innova, Oak Brook, IL. An HVP is a plant protein, or a blend of plant proteins, that has been hydrolyzed, or digested, and neutralized, resulting in a combination of smaller amino acids and peptides. The hydrolysis can be done via enzymes or acid hydrolysis. Common protein sources for HVP are corn, soy and wheat.

As a flavoring agent, HVP provides a general noncharacterized meaty/poultry profile, Glickley continues. As a flavor enhancer, HVP allows the customer to add savory enhancement to a product without having to add MSG or more salt to their product. When used in combination with a flavor, HVP provides the background enhancement that rounds out a flavor profile. The process that creates each HVP determines if the flavor-enhancement profile is light, dark, meaty or beef-like, or more like poultry or pork.

HVPs work as flavoring agents and enhancers in a wide array of applications. Recommended applications that benefit from HVP include soup, sauces, gravy, snacks, side dishes, marinades, rubs, frozen entrees and meal kits, says Glickley. He adds that HVP is comprised of 30% to 35% protein, and can be used to increase the protein content in some applications. They can also enhance poultry or meat notes in vegetarian applications.

Animal-based options 

Egg white, or albumen, consists nearly exclusively of water and protein. Glenn W. Froning, Ph.D., food science and technology advisor, American Egg Board, Park Ridge, IL, says the two top applications of egg white are foaming and gelation, or binding, in surimi and meat products. He adds that the desired functionality, high-foaming or highgelling, can be achieved by proprietary methods, and that hotroom pasteurization improves both.

Whipping air into egg white causes the proteins migrate to the interface of the air and water, with the hydrophobic groups toward the air and hydrophilic groups toward the water. The molecules at the interface unfold, or denature, to form a film that traps the air. The foaming ability is diminished by contamination by the yolk and enhanced by whipping aids, such as sodium lauryl sulfate, according to Froning. Fresh, frozen and dried egg white can all form a foam, he adds. Meringues are based on an egg-white foam. When heated, the protein denatures and aggregates to form a gel that binds the ingredients together. Egg whites can also clarify broth by trapping particulates as they set. Lysozyme, an enzyme in egg white, lyses certain bacteria. Lysozyme is routinely separated using ion-exchange resins for food-preservation applications, such as inhibition of gas-producing microorganisms in cheese, Froning explains. It is also known to be effective against certain pathogens, such as Listeria monocytogenes.

Gelatin, derived primarily from collagen in pigskins and cattle hide, results when collagen is heated and partially denatured. Gelatin is categorized by typeA or Band bloom strength. David Poppen, Midwest sales and technical service manager, PB Leiner USA, Davenport, IA, explains that, although type A and B gelatins may differ in viscosity, color and clarity for a given gel strength, the definitive distinction is the isoelectric point. Type A gelatin has an IEP between 8 and 9, whereas type Bs is 5. The gelatin molecule has a positive charge at pHs below the IEP, and negative charge at pHs above the IEP, he says. The variation in charges affects the gelatin performance and ingredient interactions. Gelatin also exhibits a loss of firmness and an increase in turbidity if the product pH is the same as the gelatin IEP.

Since most food applications are acidic, type A gelatin is the most widely used. However, Poppen counters that type B gelatin works better when used in conjunction with anionic polysaccharides, such as carrageenan. The bloom is the strength of the gel, and he says most food applications use gelatin with a bloom strength between 200 and 275. Increasing the concentration of the gelatin also increases the gel strength, and gelatin with different blooms can have similar strengths by adjusting the concentration.

The most common gelatin applications are confections, such as gummy candies, and gelled desserts. Gelatins melting and functional properties make it a key ingredient in many low-fat products. For example, gelatin is widely used as an emulsion stabilizer and texturizer in low-fat butters and margarine products, Poppen says. The fatlike melting properties of gelatin provide a creamy mouthfeel on consumption, resulting in a texture which is similar to that of full-fat products. Gelatins stabilizing ability also inhibits the breakdown of the emulsion on storage and when the product is spread. The level of gelatin in low-fat spreads is higher in products with more water, to maintain product integrity and sensory appeal. Gelatin is also compatible with milk proteins and effectively stabilizes dairy products.

The key to maximizing the benefits of gelatin is proper dispersion and hydration, Poppen says. Proper dispersion of the particles prevents clumping and allows for complete hydration. Hydration refers to the individualization of the macromolecules in the aqueous environment using an adequate agitation, he says, adding that the rate of hydration depends on mesh size, time, water temperature, shear, speed of agitation and other ingredients competing for water. Acids can accelerate viscosity loss and gel strength due to elevated temperatures. Acids should be added near the end of the process, to avoid unnecessary hydrolysis of the gelatin protein.

The smaller molecule of hydrolyzed gelatin creates new applications as a functional ingredient and also as a protein source for nutrition products. Standard gelatins have a molecular weight of over 100,000 Daltons, while the hydrolyzed gelatins are 15,000 or less, Kevin Paulsen, specialty product manager, PB Leiner USA, explains. Hydrolyzed gelatins no longer have any gel strength so their functionality changes. Adding the low-molecular- weight hydrolyzed gelatin to nutrition bars not only provides a source of protein but helps keep the bars soft and pliable throughout their shelf-life.

Hydrolyzed gelatin is non-allergenic and might contribute to the maintenance of healthy joint function by supporting cartilage building. Paulsen cites the following applications for liquid hydrolyzed gelatin: protein bars; body-building supplements; weight-loss products; and institutional-care protein supplements. The neutral-flavored liquid is available in viscosities to fit the application requirements. The benefit of formulating a protein drink with hydrolyzed gelatin is that it is easier to develop a high-protein, high-solids drink without building viscosity, he says. If you are producing a liquid product, the liquid gelatin hydrolyzates provide a ready-to-use ingredient that does not need to be rehydrated, saving production time and costs.

Milking dairy ingredients 

Milk proteins exist in two fractions: 80% casein, 20% whey. The casein forms aggregates with calcium phosphate called micelles in milk. Casein precipitates at its IEP of 4.6, or coagulates from rennet to make cheese; this effectively separates the casein from the whey. It has both polar and nonpolar groups, and is an effective emulsifier. Casein precipitated by acid has low solubility and is used for texture and dough-forming in flour-based applications. Caseinates, the salts of acid caseins, have good solubility and heat stability. Sodium, calcium and potassium caseinate are the most common, and they can stabilize emulsions and bind water.

Historically, whey was a waste product of cheese manufacture. A closer look at the nutritional benefits of its proteins has spurred the growth of whey-protein-containing health products and supplements. Whey contains a significant amount of branched-chain amino acids (BCAAs), known to assist in the building of muscle mass. Plus, Theres a lot of ongoing research substantiating the health benefits of whey protein, not just for muscle building and recovery, but also for weight loss, says Steve Dott, vice president, Grande Custom Ingredients Group, Lomira, WI. Thats the next real big breakthrough in whey nutrition. Whey protein will help you lose weight while retaining more lean body mass, and make you feel satiated longer between meals.

The individual proteins that make up whey boast some impressive health benefits. Immunoglobulins, which make up a significant portion of the whey protein, enhance immunity. Lactoferrin acts as an antimicrobial, due to its affinity for iron, and lactoperoxidase is an enzyme that catalyzes the production of a bacteriostatic compound. Glycomacropeptide (GMP) stimulates the release of cholecystikinin to signal satiety to the brain, and also supports beneficial bacteria in the gut. Lactokinin in whey, like casokinin in casein, inhibit the angiotensinconverting enzyme (ACE), and ACE inhibitors lower blood pressure. Gwen Bargetzi, director of marketing, Hilmar Ingredients, Hilmar, CA, says these components are intrinsic to whey protein, and can be selected for by fractionation during manufacturing.

Whey proteins provide functionality when manufactured in a way that prevents heat denaturation. These have good hydration and emulsification properties, and are exceptionally soluble at low pH. Grace Harris, manager of applications and business development, Hilmar Ingredients, notes: Whey protein, unlike other protein types, is stable across a wide range of pH, making it especially versatile. Fruit-based drinks are a good example; a difficult acid environment for other proteins, but one where whey protein is quite successful in fortifying and adding functionality. Whey proteins are also used to provide heat-stable gels and emulsions in dairy applications. In ready-to-drink products, whey protein withstands pasteurization temperatures, and in ice cream provides freeze/thaw stability. In addition, crisps containing from 25% to 80% protein are produced from whey.

The unique, nutritional profile of whey is the main advantage of whey crisps over other crisps used in the same applications, Dott says. The neutral, mild dairy flavor allows the crisps to be used in sweet and savory applications. The crisps can be made in a broad range of shapes, sizes, colors and flavors. The main areas of application for the crisps are nutrition bars and cereal, but they could also replace cereal-based snacks.

Whey protein hydrolysate is a protein that has been partially predigested and broken down into di- and tri-peptides, as well as free amino acids, explains Harris. She adds that different degrees of hydrolysis will provide different impacts on flavor, molecular weight profile, and functional properties. In addition, whey protein hydrolysate acts as a softening agent in high-protein bars. The hydrolysate used for that application has low water binding to allowing more free moisture in the bar. A predigested protein also assists those who need more available protein, such as infants and those with compromised digestive systems.

Some whey protein ingredients function as flavor enhancers. Whey protein hydrolysate developed for flavor enhancement generally has a fairly high level of hydrolysis, Bargetzi says. This is necessary to release amino acids that aid in flavors. Approximately 0.5% to 2.0% of whey protein hydrolysate can contribute brothy, meaty, bitter and salty notes.

A natural flavor enhancer derived from whey can be used to drastically reduce salt or as a healthy alternative to monosodium glutamate, says Dott. The number of nutritional and functional benefits from protein continues to increase as individual proteins are separated from the source material and studied. Proteins are essential to human health, and specific proteins possess some intriguing properties. In many applications, proteins also improve texture, stability and flavor. Proteins give the developer a versatile tool for creating healthier, appealing foods. 

Karen Grenus, Ph.D., has eight years combined experience in applied research and product development in the area of dry blends for savory applications. She holds a doctorate from Purdue University in Agricultural and biological Engineering.