It turns out that there are still new frontiers of fruit to be explored right here on Planet Earth. You just have to look deeply enough into Africa:
Chocolate berries (Vitex spp)
Scattered across tropical Africa, these trees produce an abundance of blackish fruit with a chocolate flavour.
Aizen (Boscia senegalensis)
A scrawny scrub in the hottest and driest regions, its fruits, seeds, roots and leaves are eaten by desert-dwellers. The yellow, cherry-sized berries are sweet and pulpy when ripe, and harden into a sweet caramel-like substance when dried.
Ebony fruit (Diospyros spp)
Best known for their valuable, jet-black wood, ebony trees also produce large, succulent persimmon-like fruit with a delicate sweet taste.
Gingerbread plums (several genera of the family Chrysobalanaceae)
Distributed throughout sub-Saharan Africa, the plums this tree produces have the crunch of an apple and the flavour of a strawberry.
Medlars (Vangueria spp)
These trees grow well in arid areas and produce fruits that, when dried, have the flavour and smell of dried apples.
Sugar plums (Uapaca spp)
Found in woodlands, this tree bears juicy fruit with a honey-like taste.
Sweet detar (Detarium senegalense)
A leguminous tree of savannahs, its pods contain a sweet-and-sour pulp which can be eaten fresh or dried.
I sense an entrepreneurial opportunity here.