If one has a food that they wish to serve, for example, chicken or fish, where some eat the skin while others do not, but the hostess wants to serve it without the skin because it looks nicer, would taking it off on Shabbos be a problem of Borer or not?
It is permitted for the hostess to remove the skin. There is controversy if the skin of the chicken is considered one type and part of the chicken, and then borer will not apply, or if it is considered a different type and then borer will apply. Many poskim hold this way that it is indeed considered one type of food. Even the poskim who hold that it is a different type, or if someone doesn’t like it, however there is a rule in hilchos borer that a peel may be removed from a food if the food will be eaten soon “miyad”. Since the hostess is removing the skin before serving it, it is considered miyad and permitted.
Igros Moshe O:Ch 4-74 ( Borer-8), Shulchan Shlomo 319-11(2), Rivivos Efrayim 4-97 (27), Hilchos Shabbos pg. 169, Orchos Shabbos Chap. 93 ftnt. 106.