Protein Quality

How much protein has to be a quality complete source of protein per serving?

I eat lots of chilli and with all the protein in beans only about 20g out of 50g per serving comes from a complete protein source.

It’s ofcourse preferable that all the protein would be complete. One way you could go is to find out which amino acids are lacking in those beans and eat another food which has those lacking aminos.

Obviously the other way is to eat more animal products and/or use a protein powder.