Egg yolk is anchored in the white by thick albumen strands. The strands should be sieved or blended into the whites so that they help to stabilize the foam.
Sieving Work the egg white through a fine sieve held over a bowl with a spoon to break up the albumen strands.
Blending Put the egg whites in a bowl and use chopsticks or a fork to lift the whites and break up the albumen strands.