handdator

Visa fullständig version : Sorry, but I’m going to have to burst another bubble here.


The Dwag
2002-04-20, 23:26
Från MaxSportsMag.

Cross Flow Microfiltration is the current flavor of the month. This is generally described as a natural, low-temperature process employing high-tech ceramic filters that filter out fat, lactose, cholesterol, and denatured proteins. The dairy companies that specialize in this material will also tell you that it has the highest levels of undenatured protein possible, the high solubility of the material serving as evidence of how undenatured it is.

Sorry, but I’m going to have to burst another bubble here. Some dairy companies are misleading the consumer by equating solubility with levels of denaturation, when it is quite simply only a milk QA test. One can test the degree of damage that heat has done to whey proteins by determining their centrifuged water solubility. This test does not determine denaturation from any other conditions (like pH changes); it determines only heat damage. Neither was it ever intended as a denaturation test; it is a heat-damage test only!

If a whey protein has been destroyed by heat exposure (not just a structural denaturing change, but absolutely destroyed), it coagulates and settles out as sediment when the whey is centrifuged. The higher the level of centrifuged sediment, the higher degree of heat destruction. The test result is expressed as a percent of the total whey protein present.

This test was developed to be run on milk powders to determine the degree of heat damage and was never intended to be run on whey protein concentrates/isolates. In milk powders, a low-heat milk powder will have a result of 1% or less (when the milk powder contains only about 6% whey protein in total … so a low-heat-damaged milk powder has up to 16% of the whey protein destroyed). A medium-heat milk powder has a result of 1%-3% … meaning that up to 50% of the whey proteins can be destroyed by heat and still the damage is considered only medium.

The whey protein processors run this test on their whey protein and show that their final product whey protein powder is 99% soluble in water, and therefore is not denatured. What they do not tell anybody is that they have already processed out all of the denatured whey protein before they concentrate down the remaining undamaged protein.

Heat-damaged whey protein just plugs ultrafiltration, microfiltration, and nanofiltration membranes, causing the processor all sorts of problems. A long time ago, people found out that filtration ran easier if they first centrifuged the whey to remove all of the heat- and pH-damaged whey proteins. They then concentrate down only the non-heat-destroyed part of the protein. That does not mean that they have concentrated down all of the protein fractions; they have concentrated only the most heat-stable parts.

After processing, they can show that the final product has little evidence of heat damage (because they already removed the heat-damaged parts). This is why these folks claim that their whey protein is "undenatured. " That is not a correct statement! The correct statement should read, "The whey protein powder that we are selling exhibits low denaturation because the denatured whey proteins were removed during processing." The best fractions of whey protein have been destroyed by the required pasteurization and removed during processing!

That is why most of the whey proteins commercially available do not contain the levels of the bioactive protein fractions that the textbooks list. Yet almost all of them can show 99% water solubility. Water solubility does not equate to denaturation! Water solubility shows only that the process did a good job of removing the denatured whey proteins during processing.

What the consumer gets from the "undenatured" whey proteins from cheese and casein is not even strictly a whey protein. In a whey protein, all of the protein fractions have to be represented in the ratios and amounts that would be expected in unprocessed milk. Such is not the case with the whey proteins coming out of the cheese and casein factories. The best fractions are gone or significantly destroyed and removed.

References

(1). Droge, W., Holm, E.; Role of cysteine and glutathione in HIV infection and other diseases associated with muscle wasting and immunological dysfunction. FASEB Journal, 1997 Nov; 11 (13): 1077-89.

(2). Sarwar, G. et al.; Influence of feeding alkaline/heat processed proteins on growth and mineral status of rats. Advances in Experimental Medicine and Biology, 1999; 459: 161-77