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Dairy Council Digest Archives
Emerging Health Benefits of Whey
Whey, Whey Products, and Whey Components
Whey Products. Whey, a by-product of cheese-making, contains protein, lactose, minerals (e.g., calcium, phosphorus, magnesium, zinc), vitamins, and traces of milkfat (1-3,6). The composition of whey products varies according to the milk source, type of cheese, and manufacturing process. There are two basic types of whey: sweet whey and acid whey (6). Sweet whey, derived from the manufacture of enzyme-produced cheeses such as Cheddar, Mozzarella, or Swiss, accounts for the majority of whey production in the U.S. (1,2). Acid whey is obtained from the manufacture of cottage, cream, or ricotta cheese (1,2).
Because of high transportation costs and susceptibility to deterioration during storage, fresh pasteurized liquid whey is rarely used as such for foods, but rather is concentrated by evaporation, reverse osmosis, or ultrafiltration to condensed products or maximally concentrated by drying. From whey, whey powder, whey protein concentrates, whey protein isolates, reduced-lactose whey, and demineralized whey are produced (2). Whey protein concentrate is available with protein levels typically ranging from 34% to 85%. This product contains some lactose, fat, and minerals. With increasing protein, the percentage of lactose in whey protein concentrate decreases. Whey protein isolate, which is less common than whey protein concentrate, contains at least 90% protein on a dry weight basis and little, if any, lactose or fat. In addition, whey protein isolates can be heated with acid or treated with proteolytic enzymes to form hydrolyzed whey proteins. As a result of new technologies, a variety of biologically active amino acids, peptides, and fractions can be isolated from whey protein (2).
Whey Components. Whey protein, which makes up approximately 20% of total milk protein, currently produces the greatest value. Because of its content of essential amino acids, the biological value of whey protein is high compared to that of other dietary proteins (7). Whey proteins have proportionately more sulfur-containing amino acids (cysteine, methionine) than casein which is almost devoid of sulfur amino acids. The essential amino acid cysteine is important for the biosynthesis of glutathione, a tripeptide with antioxidant, anticarcinogen, and immune stimulatory properties (2). Whey proteins are also a good source of the branched chain amino acids, isoleucine, leucine, and valine (2). Branched chain amino acids are unique because they help minimize muscle wasting under conditions of increased protein breakdown, which makes whey particularly beneficial for athletes (2). Also, compared to casein, whey proteins are “fast” proteins which rapidly empty from the stomach intact and transit to the upper intestine (8). This unique feature of whey protein contributes to the retention of whey protein and peptide bioactivity within the gut (2).
Emerging research findings – largely from in vitro, experimental animal, and limited human studies – suggest a number of beneficial bioactivities of whey and whey components.
Whey protein consists of several different proteins, including beta-lactoglobulin, alpha-lactalbumin, immunoglobulins, bovine serum albumin, lactoferrin, and lactoperoxidase, as well as glycomacropeptide. The latter is a casein-derived protein released into whey during cheese manufacturing. In vitro and/or experimental animal studies have identified specific biological activities for each of these proteins. Beta-lactoglobulin, which comprises about half of total whey protein, is a retinolbinding protein thought to play a role in the absorption and availability of vitamin A (2,3). Alpha-lactalbumin accounts for about 25% of total whey protein and is used commercially in infant formulas to make them more similar to human breast milk (2). This protein also binds calcium, zinc, and other minerals (3). Recently, alphalactalbumin has been associated with stress reduction, anticancer, antimicrobial, and anti-viral activities, and immunomodulation (3). The immunoglobulins in whey (i.e., IgG1, IgG2, IgGA, and IgM) have shown antimicrobial activity and may neutralize toxins and viruses (2,3,7).
Lactoferrin, an iron-binding whey protein, is the focus of considerable attention as a bioactive whey component (1-3,7,9). Multiple biological functions have been ascribed to lactoferrin, including antibacterial, antiviral, immunomodulatory, anti-cancer, and antioxidant activities, as well as stimulation of the growth of beneficial intestinal bacteria (e.g., Bifidobacteria). The major use of lactoferrin is in infant formulas to provide a formula similar in protein composition to human milk and to increase iron absorption (1-3,9). Lactoferricin, a peptide derivative of lactoferrin, is reported to exhibit numerous biological activities in common with those of lactoferrin (10).
Lactoperoxidase, a secretory enzyme in whey, is a natural antimicrobial agent used as a cavity-inhibiting ingredient in dental products (1-3,11). Glycomacropeptide (GMP), often referred to as casein macropeptide, is present in whey due to the action of the enzyme, chymosin, on k-casein during cheese-making (1-3,7,12). Because this peptide lacks the amino acid, phenylalanine, it is used to formulate foods containing protein for patients with the disease phenylketonuria (PKU). GMP has been shown to exhibit antibacterial, antiviral, and immunomodulatory activities, as well as promote bifidobacterial growth under experimental conditions (2,7,12).
In addition to protein, whey is a source of other value-added dairy ingredients including lactose, lipids (e.g., sphingolipids, conjugated linoleic acid [CLA]), and minerals such as calcium (1-3). Lactose serves as a source of energy, acts as a prebiotic encouraging the growth of beneficial bacteria, has a relatively low glycemic index and low cariogenicity, and is a precursor for other bioactives such as lactulose and lactobionic acid (1,2). Although the concentration of lipids in whey is low, the bioactivities of sphingomyelin, a phospholipid, and CLA are of interest as potential health-promoting components (2,3,13-15). Calcium may help protect against several major chronic diseases including osteoporosis, hypertension, and some cancers, among other diseases (16,17).
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