I've just checked the four leading online culinary glossaries, and "body" doesn't appear; I conclude that it has no meaning peculiar to the craft. Of the definitions listed in the WR dictionary, I'd say this one probably applies: substance; consistency or richness
I agree with Parla as to the most suitable dictionary definition:
"substance; consistency or richness: a wine with good body."
It's quite common to talk about an ingredient adding body to a dish; especially one that has a substantial amount of liquid, like a stew. A stew with "body" is the opposite of a watery stew. "Body" involves depth or intensity of flavour.