FL-122 discusses copyrights in regards to recipes. (I have no idea what FL stands for.)
For further information about copyright, see Circular 1, Copyright Basics. Note that if your recipe has secret ingredients that you do not want to reveal, you may not want to submit it for registration, because applications and deposit copies are public records.
Deposit requirements depend on whether a work has been published at the time of registration:
- If the work is unpublished, one complete copy
- If the work was first published in the United States on or after January 1, 1978, two complete copies of the best edition
- If the work was first published outside the United States, one complete copy of the work as first published
- If the work is a contribution to a collective work and was published after January 1, 1978, one complete copy of the best edition of the collective work or a photocopy of the contribution itself as it was published in the collective work