The American Herbalist’s guild has an archive of free webinars (only some with accompanying .pdfs, though)!! Go look!
Foodtimeline.org covers everything from water and ice to cronuts. This is a preserved and (as of 2013) updated work started by the late Lynne Olver. From the webpage:
Thee Food Timeline was created and maintained solely by Lynne Olver (1958-2015, her obituary), reference librarian with a passion for food history. About it she originally said ” Information is checked against standard reference tools for accuracy. All sources are cited for research purposes. As with most historical topics, there are some conflicting stories in the field of food history. We do our best to select and present the information with the most documented support. Heritage Radio interviews Food Timeline editor (2013).
Here’s a link to what Olver found about Celtic cuisine, ancient and “newer”.