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Does Whey Have Casein? | Ask The Fitness Nerd

February 10, 2009 on 7:48 am | By Matt | In Ask The Fitness Nerd, Diet and Nutrition, Protein | No Comments

Does Whey Protein Also Contain Casein? We Sort Out The Milk Protein Mystery Once and For All.

Dear Fitness Nerd,

I’m a little confused about whey and casein protein. Does whey also contain casein? And vice versa?  All I know is that both whey and casein are in milk.  Can you help me sort this out? — Janine (Dunwoody, GA)

You’re right that both whey and casein are proteins in milk.

But the important thing to grasp is that they are two totally different kinds of protein.

So in their purest form – isolated from the milk itself (for example in protein powder supplements) — whey typically doesn’t contain meaningful amounts of casein. Same goes for casein in regards to whey content.

Understanding Milk Proteins: Whey vs. Casein

The easist way to think about this is in the context of milk.

Milk contains about 80 percent casein protein, and 20 percent whey. Under normal conditions, you would never be able to differentiate between the whey and casein in milk visually. It just looks … well … liquid and “milky.”

However, when you add an acid or enzyme like rennet (which is used in cheese production), the milk will curdle. This literally separates the whey from the casein proteins.

The result is that the whey — which is a semi-clear liquid — will rise to the top, while the casein (which is heavier and coagulates in the presence of an acid or enzyme) will usually sink to the bottom.

In cheesemaking, the whey is siphoned off from the casein, and the solids are then drained through a cheese cloth, further extracting any residual whey or water and leaving the firm casein solids, which are then shaped into blocks of cheese (there are more steps, but I won’t get into them here.) 

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