Blood spots are not harmful and will disappear with age. Egg yolks add tenderness and color to baked goods. Some recipes call for beating egg yolks and sugar until thick, light, and forms a ribbon. The egg white is mostly protein. To get maximum volume when beating egg whites they should be at room temperature and make sure your bowl and beaters are clean and free of grease.
Copper is the best type of bowl to use.
If whites are over beaten the protein molecules will lose their elasticity and the whites will become dry and flaky and won't hold as much air. If this happens, add another white and beat again only until the whites are creamy and glossy. When adding beaten egg whites to your batter, always fold the whites into the heavier mixture. Not vice versa. Fold gently and quickly so as not to deflate the mixture.