Ion-exchanged whey protein isolate, micro/ultra filtered whey protein isolate...what's the big deal? Whey protein is whey protein, right? Wrong. There are important differences between these two types of whey protein isolates (WPI). The choice of which to use depends on many factors, but there are significant nutritional implications to the choice.

Production Of Whey Protein Isolate

Sweet whey, upon separation from the cheese curd, is subjected to various methods to remove any remaining cheese "fines," pasteurized and then the fat is removed by centrifugal separation. Following this pretreatment the fluid material is suitable for the production of many whey products (such as lactose, reduced lactose whey, 25-80% whey protein concentrates (WPC), various demineralized wheys, milk mineral concentrates, ethanol and most recently WPI). The production of WPI is accomplished by one of two processes:

1) Ion exchange (IE), followed by concentration and spray drying, or

2) Microfiltration followed by ultrafiltration (MF/UF) and subsequent spray drying.

The ion exchange process for WPI production is very similar to that used for the production of "soft" water, where the calcium and magnesium ions (i.e. "hardness") are removed from the water by adsorption on a static resin bed replacing sodium ions at neutral pH. In the production of WPI by IE, the pH of the pretreated whey is adjusted to 3-3.5 with phosphoric acid and it is introduced into a stirred resin tank and some of the proteins are adsorbed. After removal of the remainder of the partially deproteinized whey from the tank, the adsorbed proteins are eluted (i.e. removed from the resin), raising the pH with a sodium hydroxide solution and the resin is thus regenerated. The pH of the resulting protein containing solution is adjusted as desired, concentrated (by ultrafiltration, reverse osmosis and/or vacuum evaporation) and spray dried. As is evident, this is a "batch" process, which uses chemicals to separate some of the proteins from the other whey components.

The microfiltration/ultrafiltration process for the production of WPI is a pressure driven membrane filtration process which consists of two "molecular sieves"; in each step differing components are removed and/or concentrated to achieve the desired end product.

The pretreated fluid whey described above still contains a measurable amount of fat (typically 0.05%). In the MF/UF process virtually all the fat remaining in the whey is removed during the MF step because it is retained by the membrane. The proteins in the defatted whey resulting from the MF step can then be concentrated by ultrafiltration to a level of greater than 90%. It should be noted that all of the water soluble proteins in whey are recovered by the "continuous" MF/UF process.

Composition

The composition of most whey protein isolates produced by either production method is compared below to 80% whey protein concentrate:

 

The main differences in the whey protein isolates prepared via the two production methods is found in the composition of the proteins. Some protein fractions are not recovered in WPI produced by the IE process, resulting in the loss of almost one-fifth of the proteins. The importance of these fractions will be presented later, but the loss of these proteins results in the following protein compositions:



Further, the different ionic conditions during the production of WPI by the two methods results in markedly different mineral compositions:

Nutritional Implications

Both IE and MF/UF whey protein isolates have high levels of all these protein fractions: alpha-Lactalbumin, beta-Lactoglobulin, bovine serum albumin and immunoglobulins.

More interestingly, and the area of greatest difference between the two types of WPI, is in the immunological and digestive implications of the proteins that are absent in IE WPI.

The three whey proteins of significance are lactoferrin (LF), lactoperoxidase (LP) and the glycomacropeptide (GMP)of kappa-casein. The peptide fragments (PF) reported above in the MF/UF WPI can also have nutritional implications.

Although lactoferrin and lactoperoxidase can be bound by the IE resin, they have isoelectric points of 7.9 and between 9.0-10.0 respectively. Therefore, in order to elute them from the resin the pH of the medium would have to be raised to at least 10 and the small amount of protein recovered for this extra effort is not economically viable. So in most cases these proteins are simply allowed to remain on the resin until the system is cleaned-in-place with strong caustic at the end of the operating period. Glycomacropeptide is not bound at all by the IE resin and is thus not recovered.

Lactoferrin binds iron very strongly, thus rendering this essential nutrient unavailable to support microbial growth. Additionally, segments of the LF molecule can exert a direct bactericidal effect on certain strains of bacteria and are also thought to inhibit the attachment of bacteria to the gut wall, therefore reducing the probability of infection. Anti-viral effects of bovine LF against several types of human viruses have been reported and LF likely exerts the effects at the level of adsorption and/or penetration of the viruses. Another biological function ascribed to LF is the protection against oxidative damage by scavenging excess iron, which catalyzes the undesired formation of free radicals from hydrogen peroxide produced as a result of microbial respiration, thus allowing the animal cell's own peroxidase to harmlessly break down the hydrogen peroxide.

The antimicrobial activity of lactoperoxidase is based on a completely different mechanism than that of lactoferrin. LP inactivates or kills a wide spectrum of microorganisms through an enzymatic action. This reaction involves two cofactors, hydrogen peroxide and thiocyanate ions, which together with LP constitute the lactoperoxidase system (LP-s). Activation of the enzyme results in the formation of hypothiocyanite, which is responsible for the antimicrobial action. The LP-s is harmless to mammalian cells and is present naturally in secretions of the exocrine glands, such as saliva, tears, sweat, bronchial, nasal and intestinal secretions. There it plays a role in the protection against microbial invasions. It has been shown that viruses can also be inactivated by LP-s.

Glycomacropeptide (GMP) is a hydrophilic peptide moiety of kappa-casein that keeps micellular casein in aqueous solution (i.e. in milk). It is its cleavage by rennet (chymosin) during the cheesemaking process, which makes micellular casein become insoluble, thus forming cheese curd. This same cleavage takes place in the stomach after consumption of milk or casein and GMP is the first hydrolysis product emptied from the stomach after ingestion. In the duodenum it stimulates the synthesis and the release of the hormone cholecystokinin (CCK). The two important physical events triggered by CCK during digestion are the release of the pancreatic enzymes and the contraction and emptying of the gall bladder/hepatic bile duct. The pancreatic enzymes are critical for the complete digestion of fats, proteins and carbohydrates and therefore the full nutritional realization of food. Also, CCK has the effect of slowing the overall digestive process by slowing intestinal contractions, thus giving the digestive enzymes more time to work on their respective substrates resulting in more complete absorption of a given digestive loading. In fact, there is interest in GMP isolated by itself as an appetite suppressant for inclusion with other foods, because by slowing digestion one perceives the "full" feeling longer following a meal, possibly discouraging between meal snacking.

The peptide fragments in the MF/UF WPI are small pieces of proteins present in the milk/whey from which this product is manufactured. These result from the action of enzymes upon the other proteins present in the medium(s) prior to drying. They are significant because they can be further digested and/or absorbed by the body faster than their intact protein antecedents. This has implications for faster recovery for athletes following strenuous exercise and individuals with compromised digestive functions. In fact, some nutritional beverages include enzymatically hydrolyzed (i.e. predigested) WPI or WPC as a portion of the compounded finished product to provide this functionality.

The mineral composition disclosed above serves to show that MF/UF WPI provides a more balanced source for electrolyte replenishing potassium and sodium, while still contributing calcium and phosphorus necessary for bone maintenance.

Conclusion

Although both types of whey protein isolates offer similar functional improvements over 80% whey protein concentrate (i.e. gelling and foaming like egg white), it is in the minor differences in protein composition that separate the two. MF/UF whey protein isolate contains the minor protein fractions (missing in IE whey protein isolates), which are important from both immunological and digestive standpoints.

What does this mean for sports nutrition? Athletes are always looking for an edge, some way to gain a fair competitive advantage and they are increasingly recognizing the importance of nutrition. Nutrition is under the athlete's control, it plays an important role in overall wellness, recovery and performance. Good nutrition gives an athlete an edge.

How to keep honing the edge becomes the next question. Micro and ultra filtered whey protein isolates are the best proteins available for athletes and other physically active people. MF/UF whey protein isolate has a more complete protein profile than IE whey protein isolate: MF/UF isolate supports the whole athlete: muscles, digestion and immune system. It helps an athlete's edge become and stay razor sharp.