Separating Green Coffee Beans by Quality
Grading green coffee involves using specific criteria to separate the coffee beans into various quality designations. This process varies in different countries and coffee-growing regions. Some regions grade their coffee based strictly upon the green coffee bean size, while others use various other criteria. Some ways that green coffees are graded are:
- Varietal (eg. Arabica vs. Robusta, and sub-varietals such as Bourbon)
- Physical size (eg. "AA" or "17/18" or "Supremo")
- Standard vs. Peaberry
- Processing method (Washed, Semi-Washed, Natural)
- Cupping Notes
- Altitude (High Grown, Strictly High Grown)
Even controlling for these factors, coffees can have distinct cupping characteristics that change from year to year and require a coffee review.
Consumers looking for ways to narrow their choices should typically choose based on Origin/Region and cupping notes.
Coffee roasting companies may find information about the unroasted green coffee important - such as the physical size, density, processing method and defects - as these will affect the roasting process itself.
Criteria Used for Grading Coffee Beans
The grade of coffee beans is a quality designation that is based upon specified criteria.
Grading criteria may include coffee bean size, coffee bean hardness (e.g., density), growing altitude, color, aroma, number of bean imperfections or defects (e.g., hollow, deformed, chipped, nicked, etc.), purity of coffee bean type/plant type (e.g., botanical variety, varietal), the number under-ripe beans and/or over-ripe beans, the processing method used to extract the beans from the coffee cherry (fruit), mildew/moldiness, moisture content, and the quality of the cup of brewed coffee produced by the coffee beans.
Coffee Grading Methods by Region
Each coffee-growing region has its own method of grading the coffee beans. This allows a country or region to take coffees from any number of farms - sometimes hundreds or thousands - and output a consistent product for coffee importers and brokers in other countries.
The Costa Rican Coffee Grading System
Costa Rican coffee beans are graded using an altitude-based system that grades by hardness.
The Costa Rican beans are divided into: Strictly Hard Beans (SHB), including beans from elevations above 3,900 feet; Good Hard Beans (GHB), including beans from elevations from 3,300 to 3,900 feet; and Medium Hard Beans (MHB), including beans from elevations from 1,600 to 3,000 feet.
A primary characteristic of high quality coffees is how fast the coffee cherry (fruit) matures, with slower maturing coffee cherry generally producing a higher quality coffee bean (e.g., brighter acidity and nicer flavor). Central American coffees in particular use the bean hardness as the basis of their grading system.
Kona Coffee Grading
Kona coffee beans are first graded by seed type as either Type I or Type II. Type I Kona coffee beans have two seeds (half-beans) per coffee cherry (fruit) and they are oval (football-shaped) on one side and flat on the other side.
The primary grades of Type I Kona coffee beans are: Prime (the lowest grade); Kona #1, a mid-grade coffee bean often sold in bulk and used in many restaurants; Fancy (also a high grade); and Extra Fancy (the highest grade).
Type II Kona coffee beans have just one whole round bean per coffee cherry. These are also known as peaberry coffee beans. Grades of Type II Kona coffee include Peaberry Prime (the lowest Type II grade) and Peaberry Number One (the highest Type II grade).
After sorting into Type I and Type II, the Kona coffee beans are sorted by size, moisture content, and purity of bean type.
The Guatemala Coffee Grading System
The Guatemalan coffee grading system defines the Strictly Hard Bean (SHB) grade to include coffee beans grown at elevations higher than 4,500 feet above sea level, while the Hard Bean (HB) grade includes coffee beans grown between 4,000 feet and 5,000 feet above sea level.
As with other coffee growing areas, the assumption is that the higher elevation bean is harder (more dense), and thus of a higher quality, or grade.
The Kenyan Coffee Grading System
Kenyan coffee beans, which are some of the world's finest, are carefully graded after harvest. The coffee beans are separated (sorted) and rated by bean size as well as color, shape, and density. The largest and best coffee beans from Kenya are graded Kenya AA.
The screen size Kenya AA, which is the highest available, sorts beans that are a bit more than ¼-inch in diameter, although the slightly smaller Kenyan AB coffee beans are sometimes rated higher for flavor.
Generally speaking, however, Kenya AA, which is grown higher than 6,600 feet above sea level, is considered to be one of the world's finest premium gourmet coffees.
While it is true in general that larger coffee beans usually contain more of the precious oils that create the brewed coffee's flavor and aroma, there are also other factors besides bean size that may be just as important to the coffee beans' quality, and professional coffee tasters (cuppers) will continue to debate whether bean size necessarily equates to a better quality of roasted, ground, brewed coffee.
Kenya E coffee beans, also called Elephant grade coffee beans, consist of the largest Kenyan coffee beans and are taken from coffee fruit (cherry) in which two coffee seeds are joined in one cherry (this is a genetic defect). Also included in the Kenya E grade are the large Kenya PB (peaberry) beans and very bold (large) Kenya AA beans.
Other Kenya Coffee Grades
Due to huge production volumes, Kenya has a large number grades that are used on a regular basis.
Kenya C coffee beans consist of thin coffee beans from Kenya B grade, while Kenya TT coffee beans are the result of using air extraction to sort out the light density coffee beans from the grades Kenya E, Kenya AB, and Kenya AA coffee beans.
Kenya T coffee beans consist of broken, faulty, thin, and small coffee beans or chips of coffee beans from the Kenya C grade.
Kenya MH/ML coffee beans comprise about 7% of a typical Kenya coffee crop and include coffee beans that either weren't picked during the normal harvest or fell from the coffee plant on their own after ripening. MH/ML coffee beans are notably sour.
Screens with Graduated Hole Sizing
Coffee beans are often separated into quality grades primarily using screens with graduated hole sizing - this separates the beans by size and shape.
Also utilized for grading the beans is a vibrating air table which uses gravity to separate and grade the beans by density. This also isolates the defective coffee beans which may be nicked, hollow, or have other imperfections, and if these coffee beans are not removed can decrease the overall quality of the coffee.
Electronic and Mechanical Coffee Bean Grading
Electronic and mechanical grading - by size, weight, shape, and color - takes place after the Kenya coffee beans are milled and isolates the best coffee beans while also removing any defective beans that may add an off-taste to an otherwise coffee.
Clearing Extraneous Materials
If the coffee beans were not cleared of extraneous materials during processing and sorting (e.g., all foreign matter such as pebbles, wood, insects, etc. removed), then this may also affect the grading of the coffee beans. Even with proper processing, it's not uncommon to receive bulk bags of green coffee beans with foreign fragments, which are mostly benign and destroyed during the roasting process.
Other Coffee Grading Systems
Other countries use other methods of coffee bean grading, many of which are described throughout the Espresso Coffee Guides Coffee and Espresso Glossary.
In coffee growing regions throughout the world both the grading and the processing of coffee beans have shown continued improvement with the introduction of new technologies and equipment. Also see Sorting.
Coffee and Espresso Brewing Tips
If you want to savor the flavors and aromas of the finest gourmet coffee beans in all the world then make sure to see our detailed section on optimal coffee brewing. You can also read detailed coffee flavor profiles of gourmet coffee and instructions on preparing some absolutely amazing Espresso Drink Recipes.