In short, if this is liquid, and not raw egg whites, they are bio-available and you are digesting the protein you are after! However, here is my long answer, if you want more information…
I am going to state this first comment: raw and liquid egg whites are not one in the same (unless you mean egg whites you crack from a raw egg). In liquid egg whites (at market, not from cracking an egg), the amino acids are conserved, as is the bio-availability. While raw egg whites present the potential for Salmonella, liquid egg whites do not.
In a raw egg there is a component in the egg whites called Avidin, and it blocks Vitamin B6 uptake. Blocking B6 can result in a vitamin deficiency. Raw egg whites also have conalbumin. Conalbumin binds to iron, making it biologically inactive. Thus, when these proteins are bound to respective vitamins(biotin for Avidin, iron for conalbumin)they become less digestible.
So, essentially when you cook egg whites, you are neutralize this components mentioned above, so that your body can safely digest the protein in an egg, and utilize those amino acids without interference of those proteins binding to said vitamins and minerals.
In liquid egg whites that are heat pasteurized, the heat kills salmonella and neutralizes the Avidin. This makes them safe and digestible. Heat is also great for eggs, because it has been show to weaken the weaken the allergenicity of egg proteins in egg whites(Liu X,2013). However, I should note that some studies have failed to find allergenic differences between fresh v. pasteurized egg white(Jurado-Palomo J, 2010).
One thing you should know about heat and protein. In the lab we use heat to denature proteins. When a protein is denatured, it essentially goes from its native (natural) folded state, to a linearized conformation (shape). This can then alter the properties of that protein, as well as function. Since denatured protein still contains all of the amino acids found in the native form, they are still nutritionally beneficial.
So, while egg proteins are considered highly digestible, we know through using the stable isotope–labeled egg protein model, that the true digestibility of raw egg protein is about 51.3 compared to 90.0 in a cooked egg (Evenepoel, 1998). This is however for the whole egg, but suggests that cooking and raw eggs provide digestible protein, but that cooked provides more, despite being a bit denatured. Why? Well, native egg protein appears to be malabsorbed to an extent.You see using the heat to denature a protein can aid in protein absorbance and digestion since heating essentially « per-digests » the protein for you (breaks it down).