Fruit for Thought: Cherimoya

Cherimoya ( Annona cheirimola P. Mill. ) is an absolutely wonderful fruit which is becoming better known in the United States . It is now produced in limited amounts in Southern California . It is thought to be native to southern Ecuador and northern Peru , and is related to some fruits in the same genus which grow in more tropical areas. Cherimoya was probably taken to other parts of the world hundreds of years ago, so it is especially well known in Asia as well as throughout South and Central America . It is produced rustically in many parts of the world, but it is produced in commercial plantings only in semi-tropical areas of Spain , Chile , Peru , California , New Zealand , Australia , and Israel .

Some closely related species are produced in more tropical areas. Atemoya is an interspecies hybrid of cherimoya and sugar apple ( Annona squamosa ). The fruit has some qualities of cherimoya, and grows in hotter, more humid areas where cherimoya cannot be grown, in Florida , Hawaii , Australia , and Israel . Guanabana ( Annona muricata ) is grown throughout tropical South and Central America . It is larger than cherimoya, but has more fibrous flesh, and a very tart flavor. It is better suited to processing, especially into drinks, than to eating fresh. Paw paw ( Asimina triloba L.) is the only Annonaceae species native to North America, in valleys in the middle and eastern U.S.

Cherimoya is actually a compound fruit in which many fruitlets have fused into a single fruit. These fruitlets are called carpels. A carpel will develop with a seed and surrounding pulp if the ovary corresponding to that carpel is fertilized. The photo shows developed and undeveloped carpels. Carpels which are adjacent to carpels with seeds may also develop pulp. This suggests that seeds produce plant hormones which lead to pulp development, and that these hormones may diffuse to adjacent carpels.
The reason we love cherimoya so much is because of its pulp, which Mark Twain described as “deliciousness itself”. Cherimoya of different varieties have different flavors, and fruit “flavor” generally has three components, sweetness, acidity, and complexity. Generally the greater of each of these, the better the flavor. Sweetness is generally and conveniently measured by refractive index, with a portable and inexpensive device. Sweetness is expressed as “brix”, which is an index of total dissolved solids in the juice of fruit.

Sweetness	Brix
Exceptionally sweet	25 - 30
Very sweet	19 - 24
Acceptable	15 - 18
Poor	12 - 15

Acidity is measured as titratable acid, which means how much base, or alkaline material, must be added to neutralize the acid in the juice. Greater acidity produces a greater “tartness” to the taste, and is complementary to sweetness. Both qualities are necessary for most palates to consider it a good taste.
Complexity is more difficult to measure. It consists of the content of a variety of different fruit compounds. It makes a fruit have a tinge of almond, or a tinge of orange, or whatever. It adds a variety of flavors to simple sweetness, and is also necessary for good taste.
The seeds are large, black, and inedible. Although some efforts have been made to develop cherimoya without seeds, or with fewer seeds, the best solution to this has remained producing very large fruit, which have more pulp in relation to the seeds. So far seeds seem to be necessary to development of fruit pulp.