Why yes, yes they do....Form a skin, sure. However when handled properly ~ excessive wrapping, slow thawing, the skin formed should be barely noticable.
By the same token, you can roll your centers and not wrap them and within a short period of time at room temp they will form a most crusty and unforgiving skin. The nasty skin can form from evaporation of moisture during the thawing, too much cocoa or 10x while rolling, exposure to air, drastic changes in temperature or seperation within the ganach ~ unstable sugar leaching. (just made that term up, but think sugar bloom, fat bloom...)
Moral of the story, wrap your centers as you produce them, keep them dry but not too dry to keep the outer skin supple. (did I just say that?)
Ganach is a funny thing. Once you have made friends and treat it with proper respect, it can be very forgiving.
If you really have a problem, melt them down, strain and make a lovely sauce, icing, mousse or filling.
Unless seriously burned or contaminated, never waste the chocolate ganach!:bounce:
bake first, ask questions later.Oooh food, my favorite!Professor Pastry Artswww.collin.edu