Our brains are clever things aren't they? Apparently the reason we often don't like a song until we've heard it a couple of times is because our brains like to know what tune is coming next; if we can anticipate the next notes we're more likely to enjoy the song.
Same thing with our taste buds.
Often you anticipate what something will taste like before you put it in your mouth and look forward to it. So when it turns out the thing in your mouth is nothing like what you expected, it can be quite a shock.
My Dad recently had this unfortunate experience when I (feeling a headache coming on) reached for my little jar of Neurofen while driving.
Out of the corner of my eye I saw Dad tip out a couple of pills and pop them in his mouth. About 30 seconds later he exclaimed "Ugh, these are disgusting!"