It's possible the food smell triggered it, but usually they have a striking response to that... like my very docile female, who just struck at (towards) me as I was pulling her rat out of the box.

Hissing seems more like a defensive response, and my younger female does that when I startle her - i.e. if I pull her hide off for cleaning, while she's sleeping inside. I wouldn't worry about it, though, unless she becomes increasingly aggressive. She may have just been in a cranky mood, as us women get sometimes. Is it possible she could be going into shed?