Why Do Coffee Beans Have Genders? What's the Difference Between Arabica Peaberries and Flat Beans?

Do Coffee Beans Really Have Male and Female Varieties?

When learning about coffee online, you've likely encountered articles claiming that "coffee beans have male and female distinctions." We all know that regular coffee cherries typically contain two green coffee beans. But could these two beans in the same fruit actually have different characteristics?

Where Does the "Male-Female Distinction" Theory Come From?

Let's examine the difference between the two beans in the image below.

The oval-shaped bean on the right is what proponents of the "male-female distinction" theory call "male beans" (公豆), while the flat bean on the left is called "female beans" (母豆). In reality, there is no such thing as male and female coffee beans! The widely circulated "male and female beans" theory originated from Southeast Asian merchants who discovered two different-looking beans among coffee lots, not two different types from the same cherry.

To sell these so-called "male beans" at higher prices, these merchants fabricated this story, claiming that "male beans are extremely rare, accounting for only 5% of total beans" to justify the premium pricing. While coffee beans don't have male-female distinctions, and these two different types don't come from the same cherry, they do come from the same tree, and that 5% rarity figure is actually accurate!

The Science Behind Peaberry Formation

Typically, one coffee cherry produces two green beans that grow flat against each other. However, sometimes coffee trees produce cherries containing only a single bean. This mainly occurs due to environmental factors or genetic influences, where one ovule within the fruit fails to get pollinated. The remaining ovule then has abundant growing space and can develop more roundly than beans that develop alongside another embryo. This results in an oval-shaped bean without a flat surface.

To distinguish them, these single oval beans are called "Peaberries," while beans with flat surfaces are called flat beans.

Size, Grading, and Market Value

Generally, peaberries are smaller than flat beans. For the same variety, if flat beans measure 16-18 mesh, peaberries will typically be around 14-15 mesh. Coffee beans are graded before sale, with higher grades commanding higher prices. Grading methods vary by producing region. So why mention coffee grading here? Because many countries use mesh size (particle size) to determine grades—larger beans fetch higher prices—but peaberries don't follow this rule!

What does this mean? Take Kenya as an example: beans reaching 16-17 mesh earn the AA grade with higher prices; followed by AB grade (15-16 mesh) with slightly lower prices; then C grade (14-15 mesh) with prices below AB. Peaberries typically measure around 14-15 mesh, which would normally place them in the C grade price range. But they're peaberries! This means that although peaberries fall far short of the mesh requirements for high grades, their unique and rare characteristics allow them to command prices comparable to AA grade beans!

This special treatment of peaberries leads consumers to assume that their flavor must be significantly better than those "ordinary" flat beans!

The Reality of Peaberry Flavor

In reality, between beans from the same origin, variety, and cultivation method (flat beans vs. peaberries), there isn't much difference in flavor—the distinction is purely their rarity. For this reason, most producing regions ignore peaberries and don't specifically sort them out.

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