In it he stated that the error was on his part and not the publishers. Because of personal issues and a rush to meet a publishing deadline, the attributions for the recipes were inadvertently left out of the file that he sent out, that there was no intention of plagiarism, and that the book will be corrected to indicate where the recipes all came from.
All of that is fine for the issue of plagiarism, and I'm glad to hear that he is correcting the omissions. However it still does not address the issue of copyright infringement. I have asked whether he will be seeking permission from the authors of the recipes for their use, or if he will be completely rewriting the recipes to make them his own work.