Proteins: Nutrition and Function

Americans have a tendency to do things in a big way, from big vistas to big cars. We've even super-sized our meals, and as our waistlines expand from our mega portions, do we slow down and call for moderation? No, in typical fashion, we call for more -- protein that is.

Low-carb, the latest diet revolution, is by default high-protein. Since all food is composed of three energy-giving components -- carbohydrates, protein and fat -- it follows that if you decrease one, the others will increase. Because of fat's satiating properties, not to mention its caloric density at 9 calories per gram versus carbohydrate or protein's 4 calories per gram, only so much fat can be added to a product. Protein, with its healthful properties, has become the star.

There's no question it is a vital nutrient, but Western countries have no shortage of protein. The amount of protein humans need varies according to our size and energy requirements, but in general we've always eaten like lumberjacks. USDA's food pyramid recommends two to three servings of these protein-rich foods: meat, poultry, fish, dry beans, eggs and nuts. A serving size of meat is defined as 2 to 3 oz., yet a steak serving at a local restaurant may range from the 8-oz. filet to the 20-oz. t-bone. Even at the grocery-store meat counter, 8 oz. is the typical serving size. In an average diet, meat or other protein-rich foods are usually consumed at every meal.

A sedentary adult will require 0.4 grams of protein per pound of body weight per day, or 52 grams of protein for a 130-lb. woman and 72 grams for a 180-lb. man. A growing teenage athlete will need up to 1 gram of protein per pound of body weight. That's the maximum usable amount for adults. Anything above that will be burned as fuel or stored as fat. One 8-oz. chicken breast, with 64 grams of protein, will, in that one meal, more than meet the 130-lb. woman's protein needs.

The Harvard School of Public Health, Boston, warns that increased dietary protein raises calcium requirements because protein digestion releases acids that are neutralized by calcium and other buffering agents. Considering that most people don't meet their calcium needs without supplementation, this caution should be heeded.

Protein is in the spotlight because it is not only healthy, but it truly is the essence of life. A major component of every cell, it's incorporated into every body part including skin, muscles, blood and hair. What's more, it makes up enzymes and hormones involved in countless reactions within our bodies. In fact, if water were removed from the human body, about 75% of its weight would be protein.

Building bases

Just as proteins are the body's building blocks, amino acids are the structural units that make up proteins. Of the 20 dietary amino acids, several are essential because they must be supplied in the diet. "If you don't get sufficient amounts of those amino acids, you can't make the proteins in the body that you are constantly breaking down and resynthesizing," explains Donald McNamara, Ph.D., executive director, Egg Nutrition Center, Washington D.C. "When you don't have the right amino acids to add one on top of the other as you make this protein chain, the body does one of two things. It either stops making the protein, or it starts breaking down protein in the body to get those amino acids so that it can make the sequence that's necessary."

Essential amino acids include: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Arginine is required for children, but not adults.

Nonessential amino acids are: alanine, aspartic acid, aspargine, glutamic acid, serine, cysteine, glutamine, glycine, tyrosine and proline. All of these are alpha-amino acids with the exception of proline, which is an alpha-imino acid.

An alpha-amino acid contains an amino group (NH2), a carboxylic acid group, and various side chains. The (NH) group in proline makes it an alpha-imino acid, though it is generally referred to as an amino acid. Peptide bonds link the carboxyl group of one amino acid with the alpha-amino of the next amino acid, or, in the case of proline, with the alpha-imino group. Chains of amino acids form proteins. These chains may be short or long, and their molecular weights may range from several hundred to hundreds of thousands of Daltons.

Proteins have several structural designations. Primary structure refers to the sequence of amino acids. In nature, proteins do not exist as a straight-line chain, but instead fold into a specific three-dimensional structure as hydrogen bonds form between the side chains of amino acids. This shape, an alpha-helix, a beta-pleated sheet, or a triple helix, is the secondary structure. These structures can fold and cross-link with one another and react with water molecules present around the protein, resulting in the tertiary structure. There are four possible interactions: hydrogen bonding between polar groups of side chains, hydrophobic interactions between nonpolar groups, salt bridges between acidic and basic side chains, and covalent bonding, such as disulfide bridges. Quaternary structure is the bonding of two or more polypeptides.

From a nutritional standpoint the primary structure -- the amino-acid composition -- is the most important, but the three-dimensional structure determines its digestibility and bioavailability. This three-dimensional structure is dynamic -- molecules can interact with each other and other components in the food system. Moreover, changes in structure can occur when the protein is subjected to heat, changes in pH or ionic concentrations. This affects the functionality of the protein making it an important consideration for food scientists.

Protein function

In and of themselves, most proteins have little impact on flavor, but they may participate in flavor-producing interactions. The hydrophobic portions of proteins can interact with lipids and contribute to the flavor of that product. The beany taste of soy flour, for example, results from the oxidation of protein-bound lipid components. Protein degradation may contribute to the flavor of the product, such as the fermentation of soybeans to produce soy sauce. Pleasant flavor compounds, like the aroma of freshly baked bread, can be created when proteins and amino acids react with reducing sugars.

The way that proteins interact with water is important to the structure of the protein. In turn, that structure affects other functional properties, but directly, it impacts the food system. Some amino acids bind more water than others. The availability of these amino acids -- for example, if the protein molecules unfold during denaturation -- allows for greater water binding. Water binding is associated with swelling, gelation and viscosity, all of which can greatly influence food   texture.

Gels form when proteins interact to the extent that they create a network and suspend water molecules. Denaturation, as well as protein concentration, determines the probability of gelation. Therefore, factors that influence denaturation, such as temperature, pH and ionic concentration, can cause the formation of gels, and the amount of denaturation will relate to the degree of gelation.

Viscosity is most simply defined as the degree to which fluid resists flow. During denaturation, the protein unfolds and unravels, resulting in greater volume and likelihood of interactions and, ultimately, increasing viscosity. On the other hand, if extreme denaturation precipitates the protein, viscosity will decrease.

Proteins can also act as emulsifiers since they contain both hydrophobic and hydrophilic structures. These structures can interact with and coat lipid droplets. Protein-protein interactions can form a film that stabilizes against coalescence and phase separation. Generally, denaturation lowers emulsification properties, but mild treatments can increase these properties by exposing beneficial hydrophobic areas.

Foam formation is similar to formation of an emulsion. Air is incorporated into the aqueous phase like the mixing of oil and water. Rapidly diffusing to the interface, the protein will unfold and lower the interfacial tension between the air and water phase.

Depending on the amino-acid and structural composition, proteins may be soluble; however, denaturation decreases solubility. The pH of a formulation is critical because proteins will precipitate at their isoelectric point.

Solubility is desirable in many applications, but not all. The texture of meat is primarily due to the structure of myosin, the major protein found in meat. Myosin contains a long, thin chain wound in a helix. This chain is so tightly coiled that water cannot interact with the amino acids, making the protein insoluble. In meat, these proteins wind around each other and produce a fibrous network. Through a function called fiber spinning, vegetable proteins are exposed to high pH to unfold the protein. They are passed through a die and forced to align, then spun into a low-pH solution rich in calcium ions. Calcium forms cross-links between negatively charged groups, and the low pH neutralizes the high negative charge. The goal is to reach the isoelectric point of the protein, to completely precipitate the protein out of solution. In so doing, the proteins cross-link, forming a network of fibers with a texture similar to meat.

Bakers have long used one of proteins' functions to create texture in dough. Gliadin and glutenin are not particularly water soluble, but they can immobilize water because deep within their structure they contain a large number of hydrophobic groups. These proteins unfold during mixing or kneading, and the hydrophobic groups aggregate. Intermolecular disulfide bonds join the glutenin and gliadin creating the cross-linked protein known as gluten. This cross-linking gives elasticity to the dough. During baking, the gluten is denatured and expands, contributing to the structure of risen bread.

Eggsactly

For functionality and nutrition, eggs can't be beat. According to McNamara, eggs contain 40 different proteins. Glenn Froning, Ph.D., professor emeritus, Department of Food Science & Technology, University of Nebraska, Lincoln, states that the different functions that eggs provide depend on the different proteins. Product designers often use egg whites for their foaming properties. Within the whites, the globulins help lower the surface tension to promote the formation of small bubbles during the foaming process and increase the viscosity. Ovalbumin and ovotransferrin provide heat-setting properties during foaming. Ovomucin provides the film that helps stabilize the foam. As little as 0.05% yolk contamination will greatly decrease foam formation. Sodium chloride decreases foam stability, while sugar delays foam formation. In drying operations, the hot-room method of pasteurization actually improves the foaming properties.

Egg whites contribute most to coagulation and so can improve binding properties of foods. "They have been used in surimi products to improve their gelation properties," Froning notes. Ovalbumin, ovotransferrin, globulin and lysozyme contribute to that binding and form a three-dimensional network during the heating process.

Emulsification properties primarily come from the lipoproteins found in egg yolk. In candy, egg-white proteins will help prevent crystallization, an adverse reaction that sometimes occurs in chocolate, though Froning says that these specific proteins have not been isolated.

From a nutrition standpoint, McNamara says that the amino acids that make up the egg's protein structure are the closest we have available commercially to the mixture of amino acids that make proteins within our cells. "When you get egg protein, you have a mixture of amino acids that's very similar to what the body needs in terms of our own composition," he says. "There's very little waste of that protein and very little breakdown to use it as energy, which will put a strain on the kidneys because you have to get rid of the nitrogen. In terms of protein quality and biological efficiency -- and in terms of protein biological value -- eggs are classified as the standard by which all other proteins are measured. The only thing known to be better is mother's milk."

Milk magic

Drink your milk was, in fact, Mother's mantra. Bovine milk has long been known for being a source of calcium and protein needed for growing bodies. Yet milk protein is infinitely more complex than just a string of essential amino acids. Emerging research is uncovering numerous protein fractions with specific functional and nutritional benefits. Moreover, concentration of these proteins by removal of lactose makes them prime ingredients for low-carb formulation.

"There are several newer products on the market," says Sharon Gerdes, technical support consultant, Dairy Management, Inc. (DMI), Rosemont, IL. "One is ultrafiltered milk, which is essentially milk where the lactose has been partially removed. Typically, in a glass of milk, lactose content can be reduced from 12 grams to 3 grams. This ingredient is being used to formulate a variety of lower-carb dairy products, such as yogurt, ice cream and milk-type beverages."

Fluid milk contains about 3.5% protein. Most simply, milk protein is broken down into two major components, casein, which comprises roughly 80% of the total protein, and whey protein at 20%. "Both of those groups are heterogeneous; the casein fraction can be subdivided into different casein families, alpha-casein, beta-casein and kappa-casein," explains Loren Ward, Ph.D., associate director of research, Glanbia Nutritionals, Inc., Monroe, WI. "Whey proteins also can be divided into various proteins, such as beta-lactoglobulin and alpha-lactalbumin, which would be the two primary whey proteins. Glycomacropeptide (GMP) also is found in relatively high concentrations in the whey but GMP originates from kappa-casein as a result of enzymatic hydrolysis during the milk coagulation step of cheese making. There are also other whey-protein fractions found in lower concentration in the whey, like bovine serum albumin, immunoglobulins, lactoferrin, lactoperoxidase, lysozyme and a variety of other peptides and proteins."

American focus has largely been on whey protein since it has been readily available domestically. Traditionally, milk-protein concentrate (MPC), caseins and caseinates have been imported from Europe, New Zealand, Australia and other countries. That's still pretty much true for casein and caseinates because of economic reasons. MPC is now commercially produced domestically. Currently, in the United States, MPC is manufactured with 70% protein, although other countries more typically produce 42% levels.

Ultrafiltrating and then spray-drying skim milk produces MPC. Treatment with acid or rennet precipitates casein from skim milk. "That fraction in itself is totally inert," says Benoit Turpin, technical director and national sales director, Euro Proteins, Inc., Wapakoneta, OH. To produce caseinates, the wet casein is reacted with a dilute alkali. For example, treating it with sodium hydroxide produces sodium caseinate. "That caseinate will be soluble, therefore, it will not be inert." Caseins and caseinates are then dried, and if necessary, milled.

"If you have some applications where people want to boost the protein content of the food system, without having that protein interact with the rest of the food system, casein would be an approach you could use," explains Turpin. "We've seen that lately, especially with baked goods. Caseinates have very good emulsification properties. Caseinates are being used in nondairy creamers and whipped toppings because of their emulsification properties and the fact they are functional with foaming and their capability to entrap air."

Caseinates are also engineered to impart subtle or extreme viscosities. By carefully selecting protein fractions from casein and whey, such as in the Complete Dairy Protein (CDP(TM)) line from Euro Proteins, manufacturers can specifically tailor functionality. "If you look at our caseinate and CDP products, both families of products are heat stable, which make them very suitable for products undergoing very harsh heat treatment, such as aseptic packaging," says Turpin.

More exciting, fractions can be selected for their ability to increase muscle synthesis, decrease inflammation, neutralize potential pathogens and viruses or modulate overall health and wellness. Ward discusses the benefits of GMP, the 64 amino-acid peptide released from the C-terminal of kappa-casein during the cheese-making process. "When you look at that peptide, it's very heterogeneous," he says. "GMP can be glycosylated with combinations of galactose, N-acetylneuraminic acid and N-acetylgalactosamine. Five different theronine residues are potential sites of post-translational modification. Some of these sugar groups mimic different types of cell receptors and will competitively bind to a Vibrio cholerae toxin, influenza virus or E. coli, and may have an influence on intestinal microflora."

Peter Huth, manager of nutrition and scientific affairs, National Dairy Council, Rosemont, IL, says that one of the ways to create these bioactive peptides in milk is through fermentation processes. This is the technology behind Evolus, a European fermented-milk beverage rich in peptides found to lower blood pressure. "The majority of those blood-pressure-lowering bioactive peptides have been in the casein fraction," says Huth. New research on the Biozate whey protein indicates that it also has blood-pressure-lowering effects because of the same bioactive peptide. "They are getting ready to publish now," he continues, "and the amount you need to consume is like 20 grams per day of this Biozate whey protein (the specific whey protein isolate used in this study) that's been hydrolyzed to get a reduction in both systolic and diastolic blood pressure in people with high blood pressure. This is the same effect that you get, and even more so, than you would in a dietary approach like a DASH (dietary approaches to stop hypertension) diet."

Additionally, Glenn Ward, senior research scientist, Land O' Lakes, Arden Hills, MN, finds there's significant information on the role of whey protein as a protein source for weight loss and insulin serum-level management, primarily because of its outstanding amino-acid profile.

Whey protein power

America has a well-developed whey industry. In the cheese-making process, Loren Ward says, the casein is retained in the cheese, with the exception of GMP, which is released during the formation of the gel to make cheese. "The curd contains the rest of the casein," he says. "The aqueous phase, the whey portion, is where the whey proteins are found. That's the stream utilized to make all of our different products."

Marcela Cota Rivas, technical and nutritional development manager, Vitalus Nutrition, Inc., Abbotsford, BC, explains that there are two processes for the manufacture of whey-protein concentrates and isolates: ion exchange and micro- and ultrafiltration processes. "When the whey is manufactured using the ultrafiltration process, most of the milk minerals are retained as well as the glycomacropeptides (GMP)" she says. "Ion exchange does not retain these. The micro- and ultrafiltration process not only keeps the minerals, it retains them in the same proportion as in the original milk," she notes, and mentions that, in some cases, whey proteins might have the ability to contain up to 1,000 to 2,000 mg of calcium per 100 grams. "Whey protein concentrate (WPC) has 34% to 80% protein. Whey protein isolate (WPI) has greater than 80%."

Loren Ward says that one of the benefits of ultrafiltration for whey protein isolate is, from a structural standpoint, that the protein has not been modified and therefore maintains its native structure.

The trend is toward purification of different protein peptides for different applications. Some of these proteins have unique bioactive properties. While some of these properties are well-established through clinical data, others are based on bench top and animal models. "More human clinical data is really needed," says Loren Ward, "to substantiate the earlier findings produced from in vitro research."

Beta-lactoglobulin is linked with blood pressure regulation. Alpha-lactalbumin is the main whey protein in human milk, and for this reason infant formula manufacturers are interested in this protein to make a more humanized infant formula. One of the bioactive properties that has been looked at is its ability to induce apoptosis in certain types of cancer cells. "Research, using human intestinal carcinoma cell lines such as Caco-2 and HT-29, has shown that alpha-lactalbumin, in a molten globule state, will actually induce apoptosis in cancer cells and will leave natural cells alone," says Loren Ward.

These areas are continually being researched with the hope that it will translate into useful products in the future. Whey protein got its healthful start in the U.S. market in the sports-nutrition area. It was recognized as a complete protein. Anecdotal data suggested whey protein would benefit muscle growth and development. "Now the science is catching up and whey proteins are recognized as an ideal protein for muscle synthesis because of the higher leucine content and the high branched-chain amino-acid content of whey proteins. There's a physiological influence obtained with whey protein that you wouldn't have with other kinds of protein," says Loren Ward.

Whey proteins are very high in leucine, an important branched-chain amino acid in muscle maintenance and growth. Beta-lactoglobulin, one of the main whey proteins, is almost 14% leucine by weight. Alpha-lactalbumin is just over 10% leucine by weight. "If you take your average protein," Loren Ward elaborates, "it will contain about 7% to 8% leucine. Research is showing that leucine is able to help preserve lean body mass and promote protein synthesis."

Cota Rivas adds: "Body builders and athletes in general consume whey protein because it contains the highest concentration of branched-chain amino acids. They are getting a protein with a high biological value. Branched-chain amino acids are taken up by the skeletal muscles during prolonged exercise, resulting in a source of energy ... they want to preserve and increase muscle mass."

One of the whey-protein fractions, lactoferrin, also has sports appeal. Primarily an iron-binding protein, it has other biological properties, such as antimicrobial activity, antiviral activity and immune system modulation. "It promotes the growth of good bacteria in the intestine," says Cota Rivas. "It's also a natural antioxidant. Most of these properties relate to its main activity, which is iron-binding." This iron-binding quality is important to athletes, because it makes supplemented iron more readily absorbed and bioavailable.

"Many consumers don't know about all the other benefits that whey protein has," Cota Rivas continues. "We're trying to educate the consumer." She explains that whey protein offers three distinct values.

First is its nutritional value. "It's one of the highest nutritional values of all the food proteins," says Cota Rivas, "and contains all the essential amino acids and a high concentration of branched-chain amino acids, and because whey is produced from milk, it also contains the milk minerals like calcium, phosphorous and magnesium."

Secondly, whey protein has bioactive value. "Whey proteins are being used because of their biological properties," continues Cota Rivas. "There's a lot of research indicating their benefits in specific diseases like HIV, different types of cancer, Alzheimer's and Parkinson's diseases. Whey proteins have immune-enhancing and antioxidant properties."

Lastly, are functional properties. Whey proteins have foaming, gelling and emulsification properties, as well as water-holding ability. And, according to Glenn Ward, whey proteins are more soluble than any other supplemental protein, especially in low-pH applications like juices. "Whey proteins are more soluble at lower pH -- at the pH of an orange juice, which is about 3.5 or 4.0 -- than either the soy or casein protein," he says.

In formulating with whey proteins, it's important to remember that they tend to be unstable at neutral-pH values and will aggregate. "High-acid beverages provide a stable environment for whey proteins," says Loren Ward. A lot of the sports-nutrition beverages and other whey protein beverages typically will have a pH value somewhere between 3 and 3.4. Under those conditions the protein is stable. You can send it through a heat treatment process and make a shelf-stable product without having the precipitation or aggregation of the whey protein. From a protein chemistry standpoint, most of the whey proteins have an isoelectric pH from pH 4.4 to 5.2. The isoelectric pH, where the protein has an overall net zero charge, results in the lowest protein solubility."

Nutritional bars are a typical application for whey protein. Historically, one of the downfalls of whey protein has been its tendency to harden over time when used as the protein source in nutritional bars. Loren Ward explains that manufacturers currently modify proteins with enzyme hydrolysis to produce a hydrolysate, or to yield a partially hydrolyzed product that provides softer bar texture. "One of the developing areas right now in the bar application is producing functional whey peptides from enzymatic hydrolysis so that whey proteins can be incorporated into a bar at a higher content and maintain the quality," he says. "In the beverage side of things, you can do the same thing with a hydrolyzed whey-protein isolate. You can make a product that is much more stable at a neutral pH than the intact protein."

Choosing an isolate versus a concentrate depends on the desired protein requirements and other attributes of the final product. Cota Rivas describes the nutrition bar ingredient selection process as choosing the highest concentrated protein product to pack as much protein as possible into a little bar. "Protein is just one of the ingredients," she cautions. "You also have sugar alcohols, coating, vitamins and minerals, etc. When you add the whey protein, you want to add as much protein as you can. This is the reason many bar formulators choose WPIs." Although whey-protein products have a bland flavor, whey-protein concentrate, with less protein and a little bit more milkfat, provides more mouthfeel than whey-protein isolate. "Many product formulators choose a WPC because of its flavor profile," she says, "but that can also be a disadvantage to other manufacturers who don't want those dairy notes. It very much depends on the characteristics of the final product."

Vegetable solutions

While whey protein is finding itself in formerly nondairy applications like fruit juice, vegetable proteins are breaking new ground. Although they've long been a staple of vegetarian diets, they are finding their way into mainstream products. As consumers become more accepting of labels listing vegetable proteins, food processors have opportunities to incorporate proteins from vegetable sources. One of the major advantages of a protein derived from a nonanimal source is it contains no cholesterol and the end user has no perception of cholesterol. Developers can choose from a number of options.

Wheat protein is available as textured wheat protein, wheat-protein concentrate and wheat-protein isolate. Steve Ham, director of marketing specialty ingredients, MGP Ingredients, Atchison, KS explains the basic process for protein extraction. The wheat is first milled and then hydrated to form a dough. Washing removes the starch from the protein. Then the protein is extruded or concentrated and dried.

Protein levels range from 60% to 70% in textured wheat protein and up to 90% in isolates. The size of textured wheat protein can range from coarse-ground material to fairly large pieces, suitable for vegetarian products for meat analogues. "We extract visual fibers to improve the texture of a meat analogue product," says Ham. "Wheat proteins have a very clean flavor profile. Flavor and texture are our selling points. Because of its clean flavor profile, potentially less seasonings are required to flavor the food products." This means that wheat can work in a wide range of applications.

Historically, product designers have most often included wheat proteins in flour-based applications, however Ham sees more potential for wheat proteins. "There's much more demand for protein," he notes. "We're broadening our perspective of where these proteins can go, and customers are more open to looking at these in a wider range than our nontraditional applications."

Functionality is also driving the use of wheat protein, which offers different functional properties including film forming, elasticity and extensibility. Partially hydrolyzed wheat protein has improved solubility for nutritional beverages. Some of these proteins also have binding applications. "Processing adjustments could be necessary, including additional moisture. Mix time could be affected," Ham cautions. "If you compare a wheat protein to a soy protein, a soy protein has gelling properties and holds much more water than wheat protein. Wheat protein is somewhat limited on its maximum water holding, so there would be additional moisture that could be added with additional use of protein, and the product attributes, like texture and volume, could be impacted."

Because most grain proteins lack essential amino acids, they are best combined with other protein products. Formulators can create complete proteins from the synergistic pairing of wheat and other complementary proteins, such as legumes, nuts, dairy or soy. "It's not always about how strong the protein is; there are other properties that it brings to the table," says Ham.

Rice protein, available with 80% protein, has a fairly bland flavor and is hypoallergenic and highly digestible. Barbara Ulen, technical sales manager, A&B Ingredients, Inc. Fairfield, NJ, notes that rice products are used in infant and pet foods. It works well in pet foods because some dogs and cats have delicate digestive systems.

In terms of applications, rice protein is insoluble. Its slightly gritty texture makes it unsuitable for clear or refreshing beverages. Ulen finds it suited for applications like nutritional bars. "It works well in baked goods," she says. Some people are using it in pasta applications.

Customizing soy ingredients

Developers are finding new applications for soy protein as well. Soy protein first found its niche in meat extension and meat analogues. Health consciousness and consumer acceptance have certainly contributed to its rise in popularity. Advances in the industry have improved the flavor and texture of soy making it suitable for more delicate applications.

In making soy protein, processors first remove the oil from the soybeans. They then grind the defatted soybeans into flour, which has about 50% protein and 30% carbohydrates. Soy protein concentrate and soy protein isolate are the products of extraction. Textured soy protein (TSP) results from an extrusion process. "Because of the high level of protein and the nature of protein in soy itself, during the extrusion process the protein aligns itself into fibers and forms a fibrous matrix that is cut into different shapes at the die," explains Brinda Govindarajan, Ph.D., R&D director, Legacy Foods LLC, Hutchinson, KS. "You have to visualize soy, higher-texture soy, as a vegetarian alternative to meat meaning it looks like meat, it has the texture of meat, and once it's flavored it also tastes like meat."

According to Cheryl Borders, manager soyfoods applications, ADM, Decatur, IL: "If added flavor is desired, the TSP can be hydrated in a flavored liquid or additional flavor added into the matrix. Flavor can be added at the point of extrusion, but a large portion is usually lost due to a pressure drop as the product exits the extruder. The use of spices and concentrated flavor systems will typically mask any off flavors."

Meat flavors traditionally help simulate beef, pork, or poultry. Imitation bacon bits are an industry standard. "Meat analogues can incorporate textured pieces made from flour, concentrate or isolate, depending on the application, production process, and flavor system," says Homer Showman, director R&D, Nutriant, a Kerry Company based in Cedar Falls, IA. These can maintain excellent texture through retorting, freezing and microwaving from frozen. Showman notes that besides meat analogues, beverages, nutritional and energy bars, bakery products, snacks and chips, cones, extruded pastas, cereals, and dairy analogues use soy products.

"Soy protein is used just about everywhere in the food and beverage industry," says Kevin Marcus, Cargill Soy Protein Solutions, Wayzata, MN. "They seem to best fit the need of consumers as far as convenience and health, sensory and flavor, but the hottest things in the last couple of years are nutritional beverages and bars."

However, manufacturers have hit a few bumps in the development road. "Nutrition and energy bars have struggled to extend shelf life without textural change," says Showman. "A new isolate from Nutriant solves that problem allowing the 'core' of a bar or confection to remain soft for extended periods."

Cargill offers yet another solution to bar hardening, an extruded product made from soy-protein isolate and rice flour with a texture similar to crisped rice. "One of the ways they've gotten around that is to go to these crisp products, which are Rice-Krispie-type products," says Marcus. "It's a different-textured bar, but it's a way to keep the bar soft and deliver the protein with less flavor."

Among the most creative ways to add soy to bakery applications comes from Legacy Foods, which manufactures simulated fruit bits. Govindarajan describes blueberry-, strawberry- and cranberry-flavored and -colored pieces for use in muffins, bagels and other baked foods. Aside from a nutritional benefit, when compared to starch-based bits, TSP is more durable in terms of holding its shape.

"Benefits of adding TSPs include their ability to bind water, provide texture, reduce cooking losses and improve the economics of the final product," says Borders. "Incorporating the TSP into the formulation will vary with the application. Some applications will allow for dry addition while others will require partial or full hydration of the TSP before adding to the remainder of the matrix. Product developers can consult with their ingredient supplier as to recommended procedures."

Showman suggests working with a soy supplier early in the development process to help ensure choosing the right ingredient for the desired physical properties, such as structuring, gelation, texture, viscosity, emulsification and water-binding. "There are soy-concentrate and -isolate ingredients designed specifically to deliver a high, low and mid-range value of each of these properties, as well as combinations of properties," he says.

Beverage formulation can prove challenging, especially as formulators strive for increasing protein levels. "The higher the inclusion rate, the more challenging the situation," says Linda Beck, technical services and quality manager, Cargill Soy Protein Solutions. "Putting soy protein into an acidic or juice-based beverage with an acidic pH is more challenging than a neutral pH." Soy protein precipitates in acidic conditions. "One of the biggest tricks of the trade is the use of pectin and other similar gum-type stabilizers to help keep it in suspension," says Beck. Aside from solubility and suspendability, Beck notes bland flavor and clean mouthfeel without grittiness or chalkiness as critical attributes. However, soy proteins from different suppliers are usually not interchangeable. "In the beverage area in particular, it's a little difficult to interchange one isolate for another," he notes.

Soy excels in these nutritional beverages and bars because of its healthy attributes. "Soy is very low in digestible carbohydrates," says Govindarajan. "Most of the carbohydrates are indigestible carbohydrates. It has about 17% dietary fiber. It's an ideal ingredient to use in a low-carb food. It's low in fat too. Not only are we getting more protein, less carbohydrates, but we're also getting less fat. It has about 9% sugars but those are not simple sugars like glucose that can be absorbed right into your body. Soy also does not contain any starch."

Also, its amino-acid profile is complete. "Soy is one of the best proteins available from plant sources," says Govindarajan. "It has all the amino acids for adults. It's a good complement to wheat or grain protein because grains are lacking in lysine." It also has phytochemicals and isoflavones associated with specific physiological benefits, like reducing heart disease, certain types of cancer, osteoporosis and menopausal symptoms.

Protein's future

It's impossible to say whether the low-carb diet has reached its peak. There are some who will certainly say that high-protein diets are here to stay. Others will caution that the American diet has always been high in protein, and perhaps more balance is needed. In comparison, Turpin finds the European high-protein approach to weight loss more successful because people tend to approach it with seriousness. Physician-monitored dietary intake and activity levels are entered into computer software programs to ascertain proper levels. "It's a very encompassing approach with a serious level of counseling," he says. "Americans still want the magic pill."

That magic pill may well be found in the health arena as research continues to uncover bioactive properties of peptides. "The demand for functional products is increasing and whey proteins provide the platform necessary to develop products to meet the nutritional, functional and health benefits that consumers are looking for," says Loren Ward.

Science aside, protein has long been a folk medicine, as exemplified in a tale told by Glenn Ward: "I remember hearing a story of a guy who was working in a plant in Holland testing equipment. This old lady would come to this cheese plant every day and get a gallon of whey from the vats. She was 89 years old. She attributed her long longevity and long health to drinking whey throughout the day. She called it her elixir of life."

Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached at [email protected].

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