Push for High Protein

September 2001

Push for High Protein

By Scott Hegenbart
Senior Technical Editor

Although protein is an essential nutrient, demand for higher levels is being driven by consumer interest in improving health. To meet this fascination with high protein diets, many food companies are seeking to boost the protein content of many different foods. Fortunately, product designers have a variety of protein ingredients from which to choose when formulating protein-enhanced food products.

Why protein?
Proteins — complex molecules comprising amino acids — function both as the primary structural material of animal tissue and as life process regulators. Proteins are essential nutrients because humans cannot synthesize essential amino acids. When consumed, the body breaks down proteins into their component amino acids, which are then used as the basis for new proteins — either to support tissue growth and replenishment, or for metabolic purposes. In recent years, consumers have turned to protein to enhance athletic performance, as a weight-loss tool and as a supplement to enhance overall health.

Athletic performance. Through exertion, athletes break down muscle. Because amino acids are necessary to rebuild muscle tissue, many athletic consumers seek high-protein foods. Although the American Dietetic Association (ADA), Chicago, maintains that sufficient nutrition for physical fitness and athletic performance can be met through diet, many athletes choose to consume protein- and amino-acid-enhanced foods and dietary supplements.

Weight loss. Among the issues of dietary protein, one of the most discussed and debated are the high-protein diets — previously popular in the 1970s — that have resurged in popularity with their promise of significant weight loss. These diets are based on the notion that carbohydrates are primarily responsible for excess weight gain — a notion that many dietitians maintain is misleading.
One of the more popular of these diets is The Atkins Diet. Originally introduced by the book, “Dr. Atkins’ Diet Revolution,” by Robert Atkins, M.D., the plan allows unlimited fat and protein intake while restricting carbohydrates. These restrictions are particularly stringent during the diet’s first two weeks.

According to Atkins, the diet works by limiting the carbohydrates that he says are the body’s primary energy source. By doing so, the body preferentially burns excess fat. Dietitians confirm that eating a higher proportion of fat and protein may indeed encourage weight loss by providing greater satiety with a lower overall caloric intake. By restricting high-carbohydrate foods and sweets, the diet also helps avoid blood sugar surges, which also may help control appetite.
A clinical study presented in 2000 lent support to the Atkins Diet as an approach to weight loss. The study, conducted at the Durham VA Medical Center, Durham, NC, was presented at the 2000 annual meeting of the Southern Society of General Internal Medicine. It demonstrated that the diet positively impacts on serum cholesterol levels, lowering triglycerides, while significantly raising high-density lipoprotein (HDL) cholesterol.

The results showed that over a four-month period, participants achieved an average weight loss of 21.3 lbs. Along with weight loss, the study showed a reduction in serum total cholesterol of 6.1%, reduction in serum triglycerides of 39.9%, reduction in cholesterol/HDL ratio of 18.9%, and a significant increase in HDL of 7.2%.

Such results run counter to concerns expressed by dietitians, who often point out these diets’ risks for heart disease due to the high intake of saturated fat. Other risks include concerns that the state of ketosis generated during the diets’ induction phase may cause fatigue, headache, dizziness, and could precipitate gout in people with high uric acid levels. High protein intake also has been associated with urinary calcium losses. Without appropriate carbohydrates, insulin-dependent diabetics could put themselves at risk of becoming hypoglycemic.

At a diet forum held in Washington, D.C. in 2000, Atkins maintained that even more studies are beginning to counter concerns and demonstrate the safety of higher-protein diets. Even the researchers behind such studies, however, believe that ongoing long-term research still is required to fully understand the benefits and potential problems of this dietary approach.

As the research and debate continues, many consumers still appear to be embracing protein as a weight-loss wonder. This is reflected by beef consumption information. According to data from the National Cattlemen’s Beef Association, Denver, U.S. beef consumption has been on an upward trend since 1999. According to data from the first quarter of 2001, this trend appears to be continuing.

Enhancing health. Consumers also are turning to protein in light of research indicating how soy protein can reduce serum cholesterol. More than 20 years of clinical studies demonstrate that soy protein can lower total cholesterol — reducing low-density lipoproteins, in particular, while raising HDL — and, thus, reduce the risk for coronary heart disease. The FDA approved a health claim covering this relationship in 1999. Since that time, manufacturers have introduced hundreds of soy-enhanced food products.

Although not to the point of having an FDA-approved claim, other research indicates soy protein has benefits beyond cholesterol reduction, including decreasing the risk for developing kidney disease and breast cancer, easing of menopausal symptoms and lowering the potential for insulin resistance in diabetics. A recent study from Oklahoma State University (OSU), Stillwater, even indicates that soy protein may help reduce the effects of osteoporosis in males.
Over a three-month period, OSU researchers administered 40 grams of either dairy or soy protein daily to 64 study participants. Among the participants given soy protein, the researchers discovered an increase in bone-strengthening growth factor. To better determine the effects of the proteins, the researchers have commenced a one-year follow-up clinical study.

Going to the source
Of the 20 common amino acids found in food, nine are believed to be essential nutrients. Different food ingredients have different combinations and quantities of these amino acids. Foods from animal sources — such as dairy foods, eggs and meat — have sufficient quantities of the amino acids essential to human nutrition. Most plant sources have lower levels of one or more key amino acids and must be combined — grains with beans, for example — to create a complete amino-acid profile. The exception to this rule is soy protein, which offers a complete amino-acid range like animal-protein sources do.

Ingredients to enhance protein content are derived both from animal and plant sources. Animal-protein sources include eggs, gelatin and milk. Most plant-based protein ingredients are extracted from soy, although corn, peas and wheat also may be sources.

Animal protein. Animal protein can be derived from meat, eggs, milk and skin. Protein ingredients usually are not extracted from meat because it typically has too much value as a whole food.

The protein in eggs generally is considered to be high quality. Although consumers often assume the whites to be the high-protein component of eggs, protein also is found in the yolk. Yolk proteins are complex, offering a rich assortment of amino acids. The whites contribute significantly to egg-protein functionality because they are largely made up of ovalbumin. This protein is responsible for the whipping ability and structure-forming properties of egg whites.
Although egg is less expensive than meat proteins, it’s not as cost-effective as vegetable-based proteins. Consequently, it isn’t often used merely as a protein enhancer for food products. However, it does find use in many specialty protein supplements designed for athletes. Here, the strong desire for eggs’ protein profile can offset the added cost.

Gelatin extracted from animal skin and other byproducts, also typically is not cost-effective as a protein supplement. Like eggs, though, gelatin has many functional properties, including viscosity building, gel formation and moisture binding. Eggs and gelatin still may be useful in protein-enhanced products because they can contribute to the overall protein content when added for their functional properties.
Dairy proteins. Although technically animal proteins, dairy proteins require more detailed discussion because milk’s cost and availability makes them more readily extracted and modified for food ingredient use. Milk’s primary proteins are casein and whey.

Caseins occur at about 3% of fluid milk, and comprise about 80% of milk’s total protein content. They are isolated from milk via acid precipitation. For greater solubility, the casein solution’s pH may be raised and the casein reacted with a salt to form calcium, sodium or potassium caseinates. The resulting casein fraction or caseinate is dried and packaged. Caseinate offers high functionality and a high protein content balanced by a generally bland flavor.

Extracted from milk as a byproduct of cheesemaking, whey contains about 1.0% protein — not a significant amount for protein fortification. Being mostly water, however, whey lends itself to concentration into high-protein powders.

Whey protein ingredients containing 35% to 80% protein are called whey protein concentrates (WPC). They are manufactured via heat concentration or ultrafiltration. If heated, WPC proteins may undergo partial denaturation, which will increase their water-binding properties — a desirable, or undesirable result, depending on the application.
Using microfiltration or ion-exchange techniques, dairy processors can concentrate whey to a protein content greater than 90% to form whey protein isolates (WPI). In addition to being more highly concentrated, the protein in WPIs has a high level of purity that enhances its use as a protein-enhancing tool. WPIs also offer many functional properties. They provide mouthfeel and texture, heat stability for retort or aseptic processing, emulsification and opacity.

In addition to concentration, processors also can isolate individual milk proteins that may offer specific benefits ranging from providing an energy boost to athletes to enhancing immune system response. Another way to enhance the performance of dairy proteins is to hydrolyze them into smaller protein fragments using an enzyme. Primarily, this makes the protein easier to digest, but also may provide more control over certain functional properties, reduce allergenicity of the protein and enhance bioactive properties.

Plant protein. Plant-based protein ingredients can be extracted from grains, such as wheat, rice and oats; and legumes, such as lentils, peas, peanuts and soybeans. In the United States, soybeans often are the protein supplement of choice for their previously mentioned availability and amino-acid profile; not to mention that soy comes with an FDA-sanctioned health claim.

Unprocessed soybeans consist of about 40% protein. For easy incorporation into food products, soy protein is available as soy flour, soy protein concentrate (SPC) and soy protein isolate (SPI).
Soy flour simply consists of ground, defatted soy flakes. It has between 40% and 54% protein and retains the soybean’s soluble and insoluble carbohydrate components. One of the earliest food-ingredient uses for soy flour was as texturized vegetable protein. This still often is used to extend the meat in mass-market frozen and canned meat-containing prepared foods.

Beyond its use as a filler, soy flour often is added to bakery foods where it can improve the texture and whiten the color of the crumb in bread. Its protein and carbohydrate combination also allows soy flour to replace a portion of the eggs and/or milk in certain bakery foods, as well as extend shelf life.

In products that aren’t baked or strongly flavored, soy flour is limited by the characteristic beany flavor it retains. Extracting the soluble carbohydrates from soy flour will yield milder-tasting soy protein concentrate.

SPCs range in protein content from 65% to 72%. Because aqueous alcohol is used to remove the carbohydrate fraction of the soybean, it leaves a protein with low solubility, but with the ability to absorb water. In addition to being a protein fortification source, soy protein concentrates can be texturized into meat extenders. In fact, the water-holding abilities of SPC-based texturized proteins make them the ingredient of choice for creating all-vegetable meat analogs.

The most highly concentrated form of soy protein is isolated soy proteins. These are formed when both the soluble and insoluble carbohydrate portions of soy flour are removed and the protein fraction further purified using acid precipitation and separation. Commercial forms of SPI typically contain 90% to 92% protein. Although its protein concentration is higher, SPI has a blander profile that makes it suitable for mildly flavored foods, such as beverages and infant formulas.

As with dairy proteins, soy proteins also can be hydrolyzed into forms that are more digestible and possess altered functional properties.

Formulation questions
To properly select the protein(s) that are used in a food, product designers must consider the desired protein content for the product’s target end-users, the functional properties of any protein ingredients, and any organoleptic changes that may occur with the addition of protein ingredients.

In the United States, the daily reference value for protein is 10% of the total caloric intake for people age 4 and older. A more precise guideline is 0.8 grams per kg of body weight. For a 2,000-calorie-per-day diet, this translates into 50 grams of protein each day. (This assumes a person at an ideal weight of around 135 lbs.) The protein content of the finished product generally should supply a reasonable portion of this daily intake for a product that is designed for the average consumer.

Different consumers will have protein requirements that vary from this general guideline. A product designed for athletes or for the elderly might contain a higher amount of protein to suit the greater protein needs of these individuals. Both the ADA and the Dietitians of Canada, Toronto, have suggested that athletes receive up to 1.50 grams protein/kg body weight. The ADA further reports that people 51 years or older should consume 1.00 to 1.25 grams of protein per kg of body weight. Depending on who is to purchase the product, adjust the protein content of the product accordingly.

Of course, if targeting a soy-based health claim, the FDA requirements are very specific. The claim requires these products to contain a minimum of 6.25 grams of soy protein per serving. The product’s serving also must contain no more than 3 grams of total fat, 1 gram or fewer of saturated fat and no greater than 20 mg of cholesterol. The regulations also restrict the product to a maximum of 480 mg of sodium per serving.

After determining how much protein is needed, select the protein, or combination of proteins that will provide the desired quantity without undesired effects on the product. This is, of course, the real trick to successful protein fortification. As discussed earlier, proteins offer many functional properties, such as whipping, water binding, texturizing and emulsifying. The trouble is, these capabilities may not be needed in the product being formulated and could have detrimental consequences.

If a product designer is creating a protein beverage for athletes, for example, he or she might select a hydrolyzed dairy protein for quick protein absorption. Unfortunately, this particular ingredient might build too much viscosity. The product designer may have to find an ingredient that is differently hydrolyzed, or replace some of the hydrolyzed protein with another source to reduce the viscosity.
In addition to affecting the texture, added protein also may change the flavor of a product. To achieve per-serving quantities that will allow a claim, some products may contain up to 25% soy protein. This may make soy’s characteristic “beany” flavor obvious.

Fortunately, many of the newer SPCs and SPIs are relatively tasteless, but changes still may occur. As with most flavor-masking challenges, it’s best to work with the flavor contributions of any special ingredients, rather than add flavors in an attempt to overpower them. For example, the beany/milky notes from soy might be used advantageously with a vanilla or chocolate flavor profile, rather than a fruit flavor. Another option is to seek out special masking agents to minimize off-flavors.

As is the case with determining protein level, keep the target consumer in mind when approaching flavor challenges. Strange as it may seem, athletes use protein beverages as part of a fitness plan and may be suspicious if a product tastes too good. (A relative of the “medicine has to taste bad” mentality.) On the other hand, a nutritional supplement for older consumers may need to be more strongly flavored to compensate for diminished taste sensation. Of course, a product targeted to consumers from cultures more acquainted with soy consumption may actually prefer the characteristic soy flavor to be more dominant.

A final point to consider is the allergenicity of any protein ingredients added to foods. Food allergies are triggered by proteins and some of the most common allergic-reaction-causing proteins come from eggs, milk and soy — which also happen to be the source for some of the most common protein-boosting ingredients.

When adding dairy protein to a product that normally doesn’t contain any dairy, for example, be careful to list the dairy ingredients on the product’s ingredient statement. Also, when putting the new product into production, make sure the production facility is prepared to provide proper sanitation to the manufacturing line when changing over from producing the protein-containing products to those that do not.

Product designers have a wide variety of protein ingredients from which to choose when boosting the protein content of the foods they create. With some attention to ingredient selection and formulation, they certainly can help consumers satisfy their desire for enhanced health without sacrificing taste.

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