Funny then that I actually got the idea that they rot the same way as prepared meals from you. What about cheese, eggs, and fish then? Do they all produce miasma when rotting? Or just fish (raw and/or prepared)?
Prepared food will rot on the same terms as meat, plants, cheese, eggs, and prepared fish. The only places where food etc. will not rot (or wither, for plants) are, as far as I am aware, in a stockpile, in a trade depot, in the embark wagon, or while being carried by a dwarf or caravan pack animal or wagon or used as a reaction component. Additionally, eggs (and only eggs) can be left indefinitely in the nestbox in which they were laid without rotting. It does not matter if it's in a container: a barrel or pot full of meat left in a corridor will eventually rot. Plants wither rather than rotting and do not produce miasma. I'm not certain whether rotten eggs produce miasma. The other categories definitely produce miasma.
While you'd expect milk and tallow to rot if left out, it seems that they don't. This is probably a bug. Nor do any of the other categories of food, including flours, drinks, seeds, and rock nut paste. Fat, raw fish, and corpses rot no matter where they are, which is why it is important to process them in their respective workshops as quickly as possible.