A good friend of mine has no sense of smell* - she's always been observed by people to be a picky eater with odd eating habits. Over time it all started to make sense. She clearly organizes things by taste bud taste and doesn't really like mixing flavors, e.g. anything with a sweet component she doesn't like unless it's a dessert, even if it's a subtle sweetness.

She can pick up on various ingredients, but she describes them in ways that are different from most people. For instance, garlic is a 'sweet' flavor to her. As with any lack of sense situation, it's difficult to really discuss with someone as the one person has absolutely no frame of reference, but from observation I've been able to see how things work.

One amusing anecdote was when we went over and she was making a cake. "What's that burning?" we asked. She had taken it out of the oven and put on a burner which was actually on. Well, the bottom half of the cake was burned to a crisp and she had no idea it was happening.

* Well she thought she had 0% sense of smell until one day she was working in a city-wide open sewer pit in a third world country. She said that she detected something unpleasant there that she thinks was a smell. So it would seem that it's really a super-super-super-super poor sense of smell.