Dry milling includes removing the parchment from the outside of the green bean, sorting out defects, and packaging. This is the final step before shipping the coffee. Most producers do not dry mill their own coffee since the equipment is expensive. At the dry mill, the coffee is often mechanically sorted to remove defective beans and separated by size and/or density (this is where Peaberry can be separated).
Peaberry, also known as caracolillo, is a natural genetic mutation that represents roughly 3-5% of any given farm’s annual production. Normally the fruit of the coffee plant develops two halves of a bean within a single cherry (flat bean), but sometimes only one of the two seeds gets fertilized developing one oval (or pea-shaped) bean known as Peaberry. In recent years, a following has developed around extremely high quality Peaberry coffees since they have a distinct sweetness relative to their flat bean counterpart.
Sorting methods include density table (aka gravity table); color variance done by eye, or monochromatic sorting done electronically with infrared; and hand sorting for size, color and visual defects. In Central America, density and electronic sorting are the most common, while in Africa it is more common to see density and hand sorting. Monochromatic sorting, a very fast and efficient method, is also done in many countries around the world. The technology uses an infrared camera to determine the color of the bean as it passes through multiple channels. If a defective bean is detected, it is automatically sorted to a separate area. Hand sorting involves people looking for visual defects in the green coffee. Hand sorting usually takes place with the green coffee on a conveyor belt moving past a number of workers.
Recently, new technologies allow us to minimize the risks involved in shipping coffee. We have had a lot of success vacuum packing some of our coffees. We also use GrainPro bags which were designed to protect commodities from water vapor and oxidation, two important aspects of coffee storage.
Dry milling can easily be overlooked, but doing it properly is critical because it can potentially ruin all of the hard work of the farmer.