Atemoyas (Annona cherimola x squamosa) are a member of the Moya genus of tropical fruits. They are often mislabeled as “custard apple,” which is an entirely different species of Moya (Annona reticulata). Atemoyas are actually a hybrid of two species in the same genus: the cherimoya (A. cherimola) and the sweet-sop (Annona squamosa). This cross was first documented by a horticulturist at Miami in 1908. Fertile seeds were planted in the Philippines, and the trees that grew were later transplanted to Florida, Israel, and South Wales. The fruit and trees were given the name “atemoya” from “ate,” the Mexican name for the sweet-sop, and “moya,” for the cherimoya. The atemoya trees were much hardier than either of its parents and could survive brief frosts. The resulting fruit looked similar to the sweet-sop, but had a superior flavor.
Atemoya trees are quite tall with drooping branches that often brush the ground. The large green leaves have an elliptical shape and numerous small hairs. The trees prefer regions with high amounts of rain and warm weather. However, they are quite susceptible to rain when their fruit is ripening, as the moisture can cause the fruit to split and spoil. The trees produce yellow flowers with long stalks in the spring. These flowers are hermaphroditic; they first open as female flowers one afternoon and convert into male flowers by the next day. Atemoya trees cannot self-pollinate and require nearby trees to properly develop fruit.
Over the course of the next few months the pollinated flower develops into an atemoya fruit. The fruit has a cone or heart shape and averages about 4 inches long. The fruit is protected by a thick skin with large bumps that resemble scales. The skin is initially a light green and turns a yellow-green when the fruit is ripe. Fruits are generally picked by hand. Care must be taken to pick only ripe fruit, as underripe fruit will darken and shrivel if removed from the tree. The skin can be easily removed by hand or with a knife to reveal white, juicy flesh that has a texture like custard. The flesh is divided into segments and several brown or black large seeds are present in each segment. These seeds are toxic and should not be eaten.
Atemoyas have a limited range of availability and can be found in Florida, the West Indies, and the Caribbean between August and October. Look for fruit that yield gently when pressed and have not cracked open. Atemoyas will ripen fully when placed out at room temperature for a few days. They keep in the fridge for several weeks. The flesh has a delicious, tropical flavor and is best served chilled. It can be served alone, in a fruit salad, or blended in drinks.
http://www.hort.purdue.edu/newcrop/morton/atemoya.html
http://edis.ifas.ufl.edu/MG332
http://www.wholehealthmd.com/refshelf/foods_view/1,1523,232,00.html