How Are Coffee Beans Graded
Coffee grading is a critical process that helps determine the quality and market value of coffee beans. The grading process varies depending on the country of origin, but generally, coffee is graded based on several key factors, including bean size, defects, moisture content, and cupping score. Here is a detailed breakdown of how coffee is graded:
1. Grading by Size (Screen Size)
The size of coffee beans is one of the primary grading factors, as larger beans are generally considered to be of higher quality. Beans are sifted through screens with different-sized holes, and each bean is classified according to the size it passes through.
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Screen size: Coffee beans are graded based on a mesh screen system, with sizes typically ranging from 8 (smallest) to 20 (largest).
- Grade 18 (18/64 inches): Often referred to as "AA" in regions like East Africa, indicates larger, premium-grade beans.
- Grade 15 or 16: Known as "AB" or "A" grades, with slightly smaller beans.
- Peaberry: A natural mutation where only one bean grows inside the cherry instead of two. Peaberries are often graded separately due to their different shape and flavor concentration( )( ).
2. Grading by Defects (Defect Count)
Coffee beans are graded based on the number and type of defects present. Defects can include physical flaws such as broken beans, insect damage, or over-fermented beans. Grading by defects is particularly important because the presence of defects directly affects the flavor and consistency of the coffee.
- Primary Defects: Include serious issues like foreign materials, black or sour beans, which can significantly degrade the quality of the coffee.
- Secondary Defects: Less severe issues like broken beans or insect damage.
The Specialty Coffee Association (SCA) uses a 100-point cupping system, and beans that score 80 or above with no primary defects are classified as specialty coffee. Lower grades are often categorized as commercial coffee, with more leniency on defect counts(
) .
3. Grading by Density
Density is another important factor, as denser beans often indicate higher quality. Coffee beans grown at higher altitudes tend to be denser because the slower growing conditions allow for more flavor complexity to develop.
- High-density beans: Tend to be more robust in flavor and are often sorted from lower-density beans. This can be an important grading factor in countries like Colombia, where altitude strongly influences quality.
4. Moisture Content
Coffee beans are also graded based on their moisture content. The ideal moisture content for green coffee is between 10% to 12%. If the moisture content is too high, the beans may spoil or develop mold during storage. If too low, the beans can become brittle and lose flavor.
- Moisture meters are used to measure this, and coffees that fall outside the ideal range can be downgraded for quality issues( ).
5. Cupping Score (Flavor Profile)
The cupping process is the ultimate test for grading coffee. Certified cuppers, or Q-graders, evaluate the flavor, aroma, acidity, body, and aftertaste of coffee beans to assign a cupping score. The higher the score, the higher the quality of the coffee.
- Specialty Coffee: Must score 80 points or higher on the SCA scale.
- Commercial Coffee: Typically scores below 80 and may exhibit more neutral or flat flavor profiles.
The cupping score considers factors like balance, sweetness, clarity, and overall complexity. This process is essential for grading specialty coffees that are intended for premium markets(
).
Coffee Grading Systems by Country
Each coffee-producing country may have its own unique system of grading based on local criteria. Here are a few notable examples:
- Ethiopia: Coffees are graded from Grade 1 to Grade 5, based primarily on the number of defects and overall quality of the beans. Grade 1 is the highest quality, typically reserved for specialty-grade coffee .
- Colombia: Colombian coffee is graded by bean size into Supremo (largest) and Excelso (slightly smaller). Both are high-quality, but Supremo beans are generally considered superior( ).
- Kenya: Coffee is graded by size and quality, with the AA grade representing the largest and best beans, followed by AB, PB (Peaberry), and others( ).
Summary Table of Grading Factors:
| Grading Factor | Description | Impact on Quality |
|---|---|---|
| Bean Size | Larger beans are often associated with higher quality | Affects flavor concentration and consistency |
| Defects | Number of defects (primary and secondary) in a sample | Defects reduce cup quality; fewer defects = higher grade |
| Density | Denser beans indicate better quality, often grown at higher altitudes | Denser beans tend to have more flavor complexity |
| Moisture Content | Ideal moisture content is 10%–12% | Affects shelf life and overall flavor retention |
| Cupping Score | Evaluates flavor, aroma, acidity, body, etc. | The most direct measure of overall coffee quality |
Conclusion
Coffee grading is a multifaceted process that takes into account physical characteristics like size, density, and defects, as well as sensory qualities evaluated through cupping. The higher the quality of the coffee, the more it will fetch in the specialty market. While grading systems vary by country, the Specialty Coffee Association's cupping score remains a key global standard for determining specialty coffee quality.
References:
- Perfect Daily Grind: How Coffee is Graded, accessed September 2024.
- Specialty Coffee Association: Coffee Standards, accessed September 2024.