The Purple Mangosteen (Garcinia mangostana), colloquially known simply as "the mangosteen", is a tropical evergreen tree, believed to have originated in the Sunda Islands and the Moluccas of Indonesia. The tree grows from 7 to 25 m (20–80 ft) tall. The rind (exocarp) of the edible fruit is deep reddish purple when ripe. Botanically an aril, the fragrant edible flesh can be described as sweet and tangy, citrusy with peach flavor and texture.

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The juvenile mangosteen fruit, first appears as pale green or almost white in the shade of the canopy. As the fruit enlarges over the next two to three months, the exocarp color deepens to darker green. During this period, the fruit increases in size until its exocarp is 6–8 centimeters in outside diameter, remaining hard until a final, abrupt ripening stage.
 Color changes and softening of the exocarp are natural processes of ripening that indicates the fruit can be eaten and the seeds are finished developing.[1]

Once the developing mangosteen fruit has stopped expanding, chlorophyll synthesis slows as the next color phase begins. Initially streaked with red, the exocarp pigmentation transitions from green to red to dark purple, indicating a final ripening stage. This entire process takes place over a period of ten days as the edible quality of the fruit peaks.

Over days following removal from the tree, the exocarp hardens to an extent depending upon post-harvest handling and ambient storage conditions, especially humidity. If the ambient humidity is high, exocarp hardening may take a week or longer when the aril quality is peaking and excellent for consumption. However, after several additional days of storage, especially if unrefrigerated, the arils inside the fruit might spoil without any obvious external indications. Using hardness of the rind as an indicator of freshness for the first two weeks following harvest is therefore unreliable because the rind does not accurately reveal the interior condition of the arils. If the exocarp is soft and yielding as it is when ripe and fresh from the tree, the fruit is usually good.

The mangosteen is another falsely claimed panacea of the conscientious but misguided natural super-fruit advocates. When analyzed specifically for its nutrient content, the mangosteen aril is absent of important content, except for the very important aspect of flavour. If you wish to read a description of the ultimate panacea attributed to mangosteen here is the reference. Probably should be under the tag of "quackery": PS: There are no xanthones in the fruit they are all in the skin. The only traditional use I am aware of is the use of the colour extracted from the skin for using as a dye for silk, which gives a glorious copper hue to the fibre.

Mangosteens are imported into the US at great cost. The preserved juice is available and affordable for many but beware of the varieties of purple coloured juice as this has been mixed with rind of the skin and in some cases of extreme consumption has been possibly indicated with illness. The juice normally is clear to whiteish.