To answer my own question: potassium rhodizonate mixed with glacial vinegar creates a visual test for lead. I assume that I could grind up the food, test the

To answer my own question: potassium rhodizonate mixed with glacial vinegar creates a visual test for lead. I assume that I could grind up the food, test the slurry and then maybe do a more in depth test involving putting the food in a kiln and testing the ash for lead (assuming you use temps low enough to not vaporize the lead, below 1750C).