I recently made cauliflower puree following this recipe.
I put florets of cauliflower in a microwave oven safe pot, together with some butter and some milk, and cooked it till more or less tender. Then I added salt, pepper, a bit of nutmeg and some cheese (I used cheddar and emmental).
At that point in time it was fine, like I had it before. About two days later, I wanted to eat the leftover puree (which I stored in the refrigerator), but its flavor had changed. There was now a distinct sharp flavor present, which reminded me of horseradish or perhaps mustard.
Does anyone know why and/or how the flavor changed?