Hi Ousaima,
a food phobia can of course have a background of trauma connected to that food, or to something your kids associate with those looks, feels, smells and tastes. When the beginning happened at a certain age or date, this may even be connected to a UDIN that happened at exactly that date, and even the date can be passed on as an information to others.
So if your kids suffer from their phobia you might ask what happened at age 1 that was nauseating?

Sometimes there is an easy answer, like when I was a school kid and was at a birthday party where we got some special deep-fried food. The next day I was very sick, probably with a flu. But since that day I wouldn't stand the smell of such deep-fried food anymore, it was associated with being sick! Nowadays I can eat that, but it's not a favourite.

Another explanation can be that your kids lack a certain mechanism to digest fresh fruit, and therefore feel disgusted by it. I also have something similar with cheese, never liked the smell and taste, and a doctor told me I'd lack an enzyme to break it down. If that happens, it also has an explanation: obviously a function-minus that persisted, usually as a warning mechanism.