Sodium stearoyl lactylate (SSL) forms strong bonds with the flour proteins during gluten development, improving dough strength. During protein denaturation at baking temperatures, these bonds weaken and SSL is able to translocate to the starch molecules, reducing their staling rates during storage 1.
Place the ice cube tray in the freezer and freeze the egg whites until firm. Pop the egg whites out and transfer them to a zip-top freezer bag and return to the freezer. Now, whenever you need one, two or three egg whites for an egg-white-only recipe, you have them, premeasured, at your disposal.
Editor: Darcy, the short answer is... yes! Like lasagna and other cheesy pasta casseroles, mac and cheese freezes well. You can freeze it in separate containers, too, for easy lunch reheating.