There are 15 jelly bean flavors to feed the blob for this achievement. they are as follows:
you will have to feed the blob all of these in the game to solve puzzles so it will come naturally. the only one you dont *have* to feed the blob is the balloon because that is just to help him catch up. so make sure you feed him that at some point.
you will not get this achievement until the last level. in the second to last level the blob turns into the mech, but you do not get the achievement until you feed the blob the jelly bean to turn him into the mech.