Is there casein in whey protein concentrate?

Yes, whey protein concentrate typically contains both whey protein and some casein protein. Whey protein concentrate is made by filtering whey, which is a byproduct of cheese production, to remove some of the lactose and fat. The resulting product is a mixture of whey protein and includes a small amount of casein protein, with the exact ratio of whey to casein varying depending on the specifics of the manufacturing process. However, whey protein concentrate typically contains substantially more whey protein than casein protein.

If you are looking for a pure whey protein powder, you may want to consider whey protein isolate, which is a more processed form of whey protein and normally contains only residual traces of casein.