Eating Blood
Regarding Prof. Ariel Toaff’s recent book, he is quoted as saying,
Although the use of blood is prohibited by Jewish law, Toaff says he found proof of rabbinic permission to use blood, even human blood. “The rabbis permitted it both because the blood was already dried,” and because in Ashkenazi communities it was an accepted custom that took on the force of law, Toaff said. There is no proof of acts of murder, Toaff said, but there were curses and hatred of Christians, and prayers inciting to cruel vengeance against Christians. “There was always the possibility that some crazy person would do something.”
I have no idea what sources Toaff used, but one source, although later chronologically, but is from the same general geographic area that comes to mind is a responsa of R. Menachem Azaria of Fano (16/17th c. Italy) who was asked about the possibility of eating salt during whose manufacture blood (animal!) was used as a clarifying agent (par. 27). He permits the use of this salt in certain circumstances for a number of reasons, but only on the condition that it not be eaten by itself, rather it be mixed into a dish. This was apparently already accepted as halakhah by the Tosafot whose opinion seems to have been to permit it without any restriction since in the cooking process the blood is burnt away. See the Tosafot on AZ 33a s.v. hai oved kochavim; Mordechai, AZ chapter 3, par. 823; Responsa of the Rama, par. 53 in the Ziv edition and the Rama on YD 134:13; Darchei Teshuva on YD 134:13, note 50 and the other sources that he brings which permit both salt and sugar in which blood was used during the manufacturing process. N.B. All of the above sources talk only about ANIMAL blood.
I am no idea about the merits of Prof. Toaff’s most recent book, but for those who would like to read something of his until his new book is translated into either English or Hebrew, I highly recommend his book Love, Work, and Death: Jewish Life in Medieval Umbria
Update: In this article Toaff seems to explain a bit more about the book and includes some comments by other historians. Toaff is quoting as saying,
“I believe that ritual murders never happened,” he said. “There is no proof that Jews committed such an act.”
What he does believe existed were anti-Christian rituals and liturgies.