"I love to eat fruits."
Translation:Me encanta comer frutas.
I made the same mistake, but I think comer (to eat) is the subject of the sentence. Thus "To eat fruits is enchanting to me" is the literal albeit clumsy translation. So there is no need for "las". This also answers the question as to why "encanta" is singular since "to eat" is singular.
The reason why you don't say "encantan" in this case is, as SaraGalesa pointed out in another reply, because the encanta refers to the act of eating--comer--and not the fruits. Therefore, even though fruits is plural, encanta stays singular because verbs are always considered singular.
As for why you can't add "las" before the "frutas", you got me stumped. Let's report it?
Feel free to correct me if I'm wrong, but in the meantime, I hope you understand a little bit better!
Rules/guidelines when we have to put "a" between a verb tense>> "encanta"; and its basic "to something>> i.e. > to eat" and when we don't. Do only certain verbs require an "a" before a "to something" verb or is it depend on situation (like the verb "tener" when you "have to do" something.) ??
The sentence is really more like "Eating fruits is enchanting to me". So, "eating" is the subject. With a verb as the subject of "encantar", you get singular agreement (third person of course): "encanta".
"Encantar", like "gustar"and "interesar", demands an explicit indirect object pronoun: "Me encanta comer frutas", "Te encanta comer frutas", etc.