Off the top of my head I can't think of a way of password protecting the DVD itself, but you can create a encrypted image or ZIP file that you can place on the DVD-R. You can create a new image through Disk Utility, click on the New+ button on top and then under Encryption, choose the level you want.
You can also create a password protected archive (ZIP, 7Z, what have you) using any of the various archive managers as well..
Would this suffice for what you are attempting to do?