Whey protein Isolate:  
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A complete protein yielding 90% protein concentration
It contains no fat and carbohydrates 
It is high in branched-chain amino acids(especially leucine).
It is considered an undenatured protein; however, if the raw material company uses a filtration process that uses heating components, it may denature the protein. 
Because components like beta-lactoglobulin, alpha-lactalbumin, immunoglobulin, and lactoferrin are proteins by definition, contrary to popular opinion, whey isolate does contain these critical cofactors.
Whey isolate may contain a tiny amount of lactose.
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Whey protein concentrate typically contains 70-80% protein, while isolate is further processed to contain 90% or more protein by weight. This additional processing in isolate removes more fat and lactose, making it lower in these components compared to concentrate.