A whey
protein isolate (often whey isolate) is a dietary supplement and food
ingredient created by separating components from milk. Whey is a by-product of the cheese-making
process. Whey can be processed to yield whey protein in three forms: whey
isolate, whey
concentrate, or
whey hydrolysate. The difference between the whey
protein forms is the composition of the product, particularly the protein
content.
Whey isolates contain the higher percentage of pure protein and can be
pure enough to be virtually lactose free, carbohydrate free, fat free, and
cholesterol free.
Whey
proteins are highly bioavailable, are very quickly absorbed into the
body, and have a high concentration of branched-chain amino acids (BCAAs) which are highly concentrated
in muscle tissue, and are used to fuel working muscles and stimulate protein
synthesis.
Production
Whey
isolates have had their base component (water) removed and are generally
considered almost lactose and cholesterol free — they are typically at least
90% protein.
Two
separation methods are widely used. One method, utilizes ion exchangers which extract native whey
protein from the whey stream according to the surface charge characteristics of
the molecule, also known as the zeta-potential.
This method uses mild pH adjustments to activate and subsequently deactivate
the attraction between the ion exchange resin and the protein molecules. In
between the temporary binding of protein to the resin, non-protein components
are thoroughly washed from the reactor. This process may or may not damage the proteins, but no scientific evidence exists to suggest that it does. Although
strong acids and bases are used for the adjustment, the pH rise itself is quite
small and within the range common in foods.
Changes in protein conformation
within this range are reversible and are not considered denaturation.
Ion exchange is highly specific to native whey proteins and is generally more
selective in what is retained during the process. This is why the process is
best known for creating highly pure whey proteins.
The second
method, membrane
filtration,
typically a combination of microfiltration and ultrafiltration, uses molecular size as the basis
for separating components from the whey stream. In the process, pressure is
applied across a membrane surface which forces smaller molecules through the
membrane while larger molecules are retained. Both methods yield a very high
protein to non-protein product ratio, although membrane filtration is somewhat
less selective allowing any molecule within a size range to be retained. One
compositional difference between whey protein isolates made from cheese whey
via membrane filtration compared to ion exchange is that membrane filtration
includes significant levels of the casein fragment caseino-glycomacropeptide
(cGMP). This fragment has a less complete amino acid profile and is low in
branched chain amino acids.
As a
dietary supplement, whey and other protein powders can be reconstituted at the
time of usage by the addition of a solvent such as water, juice, milk, or other
liquid. As a food ingredient, whey powders are easily mixed or dissolved into a
formulated food.
Function
Whey
protein is popular among athletes today because of its ability to be digested
very rapidly and help return the post-workout body back from a catabolic (muscle-wasting) state to an anabolic (muscle-building) state. Whey protein isolates are
also widely used in infant formula to provide a natural source of amino acids
for optimal growth and development, as well as for protein fortification of
bars, beverages, dairy products, extruded snacks and cereals and other food
products.
