Forklore: All that rot
Two of the creepiest-sounding foods of all time were the medieval Near Eastern condiments murri and kamakh. They started as raw barley dough, wrapped in fig leaves and stored in a box for 40 days. When the dough had thoroughly rotted (turned white with "red veins" running through it), it was ground up and rotted some more.
To make murri, you added water, salt and spices and put the stuff on your rooftop in the hottest part of summer for another 40 days, adding fresh water as needed, until it turned black and bubbled. It was used like Worcestershire sauce.
Kamakh was made the same way but with milk. After 40 days, it would turn red, and then you would flavor it with herbs, onion, garlic, cheese or even rose petals. Kamakh was eaten on bread.
These condiments probably arose on the model of the Greek sauce garos, which was made from salted fish. But like the modern Vietnamese nuoc mam or Thai nam pla, garos was perfectly wholesome. Rotted grain, by contrast, is rife with aflatoxins, the most virulent carcinogens known. Probably people didn't notice how dangerous these condiments were because in the Middle Ages few lived long enough to get cancer.
They disappeared around the 14th century. We don't know why; maybe people just got tired of their admittedly loathsome appearance. There was an anecdote about a Bedouin who was shown kamakh and told what it was. "I know it is kamakh," he said. "Which of you kamakhed it?"
-- Charles Perry