Hello, I have been making a traditional three-strand Challah. It tastes great, but its appearance is unsatisfactory. All along the center of the braid, when looking from above, there is a fairly wide crack. The egg white I brush on the loaf prior to baking of course does not include the crack, so the color along the crack is much lighter than the rest of the loaf. What can I do to avoid the crack? I have been trying to braid it tighter and tighter, but that doesn't seem to help. I never see it on professionally made loaves... Thanks!