According to the U.S. Copyright Office at http://www.copyright.gov/fls/fl122.html:
"Mere listings of ingredients as in recipes, formulas, compounds or prescriptions are not subject to copyright protection. However, where a recipe or formula is accompanied by substantial literary expression in the form of an explanation or directions, or when there is a combination of recipes, as in a cookbook, there may be a basis for copyright protection."

And from: http://smallbusiness.findlaw.com/copyright/copyright-realworld/recipe-copyrighting(2).html
"To what extent compilations of recipes are protected is also unclear. A compilation of facts can have copyright protection, even though the individual facts themselves cannot. But in the case of a compilation, the ordering of the factual information is what is protected, rather than the facts themselves. Thus, while the author of a collection of recipes would likely be protected against someone else removing the cover, copying the recipes, and sticking a new cover on them, the recipes would not be protected from all use by others. A reviewing court would be interested in how much creative expression the author included in addition to, and in presenting, the recipes; it would then look at how much of this information the other author or publisher used, and how closely it resembled the original work.

The short answer is that a single recipe is unlikely to receive much, if any, copyright protection, and a collection of recipes will be protected in its creative aspects, but less protected as to the specific ingredients and steps required to prepare a given dish. An author or cook considering publishing his or her recipes should approach the subject carefully. "