Dear Rich: I have a question. I read that somebody was suing Jerry Seinfeld's wife over her cookbook. That makes me nervous because I wrote a cookbook and borrowed a lot of recipes from other places. Aren't all recipes in the public domain? I'm so glad you asked. As the U.S. Copyright Office explains, individual recipes are hard to protect because no matter how delicious the results, they often lack the necessary literary expression. (An unpublished recipe can be protected under trade secret law but that means all your chefs have to sign NDAs and even then it's not foolproof.) A collection of recipes, as in a cookbook, can be protected. That protection is stronger if the author adds original literary commentary and uses creativity in the selection of recipes. Beware, some cookbooks raise additional legal liability issues.
P.S. For a thorough analysis of the Seinfeld case, check out this article.