Purple mangosteen

The purple mangosteen (Garcinia mangostana), colloquially known simply as 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 fruit, which is not edible, is a deep reddish purple when ripe. The fragrant edible flesh that surrounds each seed is botanically endocarp, i.e. the inner layer of the ovary. It is sweet and tangy, juicy, and somewhat fibrous.

The purple mangosteen belongs to the same genus as the other, less widely known, mangosteens, such as the button mangosteen (G. prainiana) or the charichuelo (G. madruno).

Maturation of the exocarp and edible aril

The juvenile mangosteen fruit, which does not require fertilisation to form (see agamospermy), 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 colour deepens to darker green. During this period, the fruit increases in size until its exocarp is 6–8 centimetres in outside diameter, remaining hard until a final, abrupt ripening stage.

The subsurface chemistry of the mangosteen exocarp comprises an array of polyphenols including xanthones and tannins that assure astringency which discourages infestation by insects, fungi, plant viruses, bacteria and animal predation while the fruit is immature. Colour changes and softening of the exocarp are natural processes of ripening that indicates the fruit can be eaten and the seeds have finished developing.[2]

Mangosteen produces a recalcitrant seed and must be kept moist to remain viable until germination. Mangosteen seeds are nucellar in origin and not the result of fertilisation; they germinate as soon as they are removed from the fruit and die quickly if allowed to dry.[3]
Only the white flesh of the purple mangosteen is edible

Once the developing mangosteen fruit has stopped expanding, chlorophyll synthesis slows as the next colour 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 the days following the removal from the tree, the exocarp hardens to an extent depending upon postharvest handling and ambient storage conditions, especially relative humidity levels. 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 the 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 edible endocarp of the mangosteen is botanically defined as an aril with the same shape and size as a tangerine 4–6 centimetres in diameter, but is white. The circle of wedge-shaped arils contains 4–8 segments, the larger ones harbouring apomictic seeds that are unpalatable unless roasted.

Often described as a subtle delicacy, the arils bear an exceptionally mild aroma, quantitatively having about 1/400th of the chemical constituents of fragrant fruits, explaining its relative mildness.The main volatile components having caramel, grass and butter notes as part of the mangosteen fragrance are hexyl acetate, hexenol and α-copaene.

On the bottom of the exocarp, raised ridges (remnants of the stigma), arranged like spokes of a wheel, correspond to the number of aril sections.Mangosteens reach fruit-bearing in as little as 5–6 years, but more typically require 8–10 years.

Nutrient and phytochemical content

The aril is the part of the fruit which contains the flavour; when analysed specifically for its nutrient content, however, the mangosteen aril only meets the first criterion above, as its overall nutrient profile is absent of important content.

Some mangosteen juice products contain whole fruit purée or polyphenols extracted from the inedible exocarp (rind) as a formulation strategy to add phytochemical value. The resulting juice has purple colour and astringency derived from exocarp pigments, including xanthonoids under study for potential disease amelioration effects.The potential health benefits of xanthones were debated in a four-part series in 2009.

Other authors proposed alpha-mangostin, a xanthone, could stimulate apoptosis in leukæmia cells in vitro.

Furthermore, a possible adverse effect may occur from chronic consumption of mangosteen juice containing xanthones. A 2008 medical case report described a patient with severe acidosis, possibly attributable to a year of daily use (to lose weight, dose not described) of mangosteen juice infused with tannins.

Source:zimbio.com