The thing about Ghana is that there are so many kinds of fruit here that are called by the local names and many of us don't know what the English/scientific names are.
Today I had what we call alasa. It is a small oval shaped fruit almost the size of a lemon (not the gigantic genetically modified kind you find in the US). It's yellowish-orange on the outside. The inside is fleshy, peach-orange coloured. There are usually 3-4 seeds inside that are black and measure about an inch and kids use it to play games. The flesh tastes slightly sour and if you chew it for a couple minutes, it turns into gum which you continue chewing for the rest of the day like real chewing gum!
I have done preliminary searches online and what I've found is a tropical fruit from Brazil called an abiu. The family is Sapotaceae. It is also know as yellow star apple in Trinidad. Apparently when it's not ripe, the fruit is gelatinous and astrigent. The only thing is that this fruit is apparently sweet when ripe. So then, the question is, is alasa abiu and if so, have we been eating the unripe fruit all this time?
6/26/2013 Addendum: Ijust wanted to reflect that from the comments down below, what the Ga call alasa is NOT the abiu/yellow star apple, Pouteria caimito but instead the white star apple, Chrysophyllum albidum, also known as the African star apple. It is also in the Sapotaceae family.
Someone asked for it's nutritional analysis in the comments section. If you have access to the Journal of the Science of Food and Agriculture, you might be able to access this 1982 Nigerian article, Nutritional value & mineral contents of Chrysophyllum albidum fruit. This other scientific article states that it has 100 times the vitamin C levels of an orange. Impressive.
People in the comments have also suggested other local names. Adisaa in Twi. Udara in Igbo (Nigeria).
Thanks readers and commentators. This has been a very exciting process. I'm especially pleased with the bonus identification of yooyi as velvet tamarind.