The cells in the pod have very rigid cell walls that don't like to budge. This ridgidity holds the plant together and upright, unlike animals who need a skeletal system to properly hold up their mushy flesh. They are filled with cytoplasm, a substance that is almost entirely water. The problem is, when you freeze water, unlike most other substances, it expands. This fills up the cells to the point of breaking, and the cell walls burst like a balloon, regardless of how quickly you froze it. All of the water then fills the space outside of the cells when you finally thaw them, and the rigidity that the cell walls supported dissapears. This makes our poor pods all limp and mushy. Of course, everything is still there, just not held up all pretty anymore. They're still great for making sauces and things and that's usually what I use frozen pods for.