Concentrating on Whey Protein Isolate

By Lynn A. Kuntz, Editor-in-Chief

Not so long ago, whey was considered a valueless cheese byproduct that was used as animal feed. However, food researchers have discovered the protein component has a high nutritional value and provides a range of functional properties that prove valuable in a number of food applications: dairy, bakery, meat, snack, confectionery, beverages, and other food and nutritional products.

Whey to isolate

Cow’s milk contains approximately 3.5% protein, about 18% of which are whey proteins, mainly lactalbumin (about 12% of the whey protein) and lactoglobulin (about 50% of the whey protein), and about 82% are caseins. During cheesemaking, the casein proteins precipitate out in the acidic environment and/or are coagulated by rennet to form the cheese while the whey proteins stay in solution. This liquid whey contains proteins, peptides, lactose, milkfat and other lipids; mineral salts and ions, such as sodium, potassium and calcium; vitamins; and water.

Manufacturers remove the water and concentrate the whey proteins, ending up with a white to cream-colored product containing 90% or more protein called whey protein isolate (WPI). A typical WPI powder will contain approximately 92.0% protein, 4.5% moisture, 2.0% ash, 1.0% fat and 0.5% lactose. However, modifying manufacturing technology creates whey isolate products with varying composition and functional properties.

“WPI composition is affected primarily by its method of manufacture,” notes Grace Harris, manager of new business and applications, Hilmar Ingredients, Hilmar, CA. “The two most-common methods of WPI manufacture are microfiltration (MF) and ion exchange (referred to as IX or IE). These methods create minimal difference in nonprotein components such as fat, lactose and minerals. By its nature, at greater than 90% protein, WPI has a very low content of these components to begin with. The main differences created by the two methods of manufacture are in the protein fraction content and some functionality.”

For example, “ion-exchange WPI contains high levels of beta-lactoglobulin and no glycomacropeptide,” explains Eric D. Bastian, Ph.D., vice president, research & development, Glanbia Nutritionals, Monroe, WI. “Alternatively, MF WPI contains lower levels of beta-lactoglobulin but high levels of glycomacropeptide.”

Enzymatic hydrolysis can also alter WPI functionality. “This allows processors to create an ingredient with widely varying functional and nutritional attributes,” says Bastian. “The degree of hydrolysis, specificity of proteolytic enzymes used, temperature and pH of hydrolysis all affect the functionality of the hydrolyzed WPI. The possible hydrolyzate variations are almost infinite.

“Mineral content can also be manipulated through membrane and electrodialysis processing techniques,” Bastian continues. “Mineral profile significantly impacts the functional properties of WPI, presenting the opportunity for specialized functionality.”

Pro nutrition

WPI can supply a concentrated source of high-quality protein for supplementation. Whey protein is a complete protein; it contains all 20 amino acids and all 9 essential amino acids in amounts proportional to the human body’s needs. Its protein digestibility corrected amino acid score (PDCAAS) is 1.14, and its biological value (BV) is 104. Whey protein also contains high concentrations of amino acids that are metabolized at high rates during exercise, particularly glutamine and leucine.