Eggs, quinoa, tofu, beans.
Yes they can be, but protein in meals is a better alternative.
Babys legs and a hint of olive oil on toast
C3
Protein powder is a means of supplementing one's diet, but it is not a replacement for food or even a meal.
Mycro-fungus It is like quorn, a alternative means of getting protein in large quantities for vegetarians.
Crude is the alternative method. This is the same thing as EIT.
Body builders are known to have protein supplements to build their body. They are formulated powder produced containing proteins of egg, soy, whey or any other protein food. This can be taken as protein shakes after workouts.
Soy protein powder is a great way to get some extra protein in one's diet. Soy is a complete protein, containing all the essential amino acids the human body needs. It is also a great alternative to whey protein to those who are dairy sensitive.
The difference between animal protein and fruit protein is foods derived from animals contain complete proteins, they often tend to be high in unsaturated fat. While protein from that of fruits and vegetables, combined to make their incomplete proteins complete, are a healthier alternative.
As your question specifically asks for a reason other than having high protein content, I would say it is because it is an alternative. Most people (aside from vegetarians) get their proteins from meats. Meats can also be a source of LDL (the bad) cholesterol and fats, which many health-conscious people like to avoid. So, if you're looking for a reason why legumes are in the protein group aside from protein content, it is because they are a healthy alternative to cholesterol-laden meats as a protein source. They are low in fat, and cholesterol free.
Beet pulp is an alternative feed to grain that is fed to livestock such as cattle and horses. It is high in nutrients and protein, which make it an ideal and cheaper alternative to corn, oats or barley.
I'm assuming you mean "protein shakes". The source of the protein in almost ALL shakes is usually Whey and Soy. Both of these contain Iodides which aggravate acne. The best alternative is a Pea or Hemp protein shake. There's a good company called Mercola that makes both.