I really enjoyed Art and Food: Rituals Since 1851, the section of the Milan Expo dedicated to art, held at the Triennale. It's a huge exhibition — we had about four hours there, and had to really rush through the second half. The exhibition begins with impressionist paintings of markets, dinners and chefs, moves through a late nineteenth century Campari bar, early and mid-century design, some fun Lichtenstein sculptures, before moving on to recent, playful pieces like Tom Sach's 'Nutsy McDonalds'. There are clips from films playing throughout, and a wonderful cabinet of nineteenth century menus and books about food.
I particularly liked Sophie Calle's 'The Chromatic Diet,' which I hadn't seen before.