From the comments.... Thanks, Mylias:
I have never had frozen mangosteen, but the fruit when stored in a fridge tastes very nice. Cool.
Mangosteen tends to damage easily. If not plucked properly, and if dropped, the latex (yellowish in colour) or one can call it the fruit sap may get into the whitish flesh and will make the fruit taste bitter and inedible. Of course the fruit must be about brownish black before you can open it and eat the whitish flesh.
In my country [Malaysia] there are two types of mangosteen. One is the one that many people often see, roundish fruit and when placed on its bottom will sit nicely. The other type is the heart shaped, and will never ever sit when placed on its bottom. And this type of mangosteen is sweeter, and it may drop to the ground when ripe and you can still pick it up, open it and eat the flesh. Or you may use a pole, to pick the fruit and if fallen on the ground will not have its sap (latex) enter the whitish flesh and the fruit is still edible, and not bitter.
My only complain about mangosteen is that its seasonal.