Green coffee, also known as raw coffee, can present various qualities, from the highest quality to undesirable defects. These defects, which affect flavor and other sensory characteristics, are crucial factors in the evaluation of coffee.
We often use “quality” subjectively, based on our preferences rather than objective criteria. However, learning to differentiate between personal enjoyment and authentic coffee quality is crucial.
I will help you understand and identify the criteria for classifying green coffee defects in this article. In addition, we will further analyze the importance of these criteria in the search for quality coffee.
Classification of green coffee defects
It is important to remember that experts in the coffee industry establish international standards to classify and evaluate coffee defects. These standards help guarantee the quality and consistency of coffee worldwide.
Among the defects of green coffee, we can find:
- Physical defects: These defects are those related to the visible characteristics of the green coffee bean. They can include broken beans, splinters, stones, sticks, and black or dark green beans.
- Chemical defects: These defects are related to the chemical composition of green coffee. They can result from problems in the cultivation process, such as the use of pesticides or inadequate fertilizers that affect the quality of the bean.
- Sensory defects: These defects affect the organoleptic characteristics of the coffee, such as its aroma, flavor, and texture. They can include unpleasant tastes and odors, such as excessive astringency, fermentation, mold, earth, or rancid taste.
- Grading defects: These defects refer to errors or inconsistencies in the sorting and separating coffee beans during the sorting process. They can include mixtures of beans of different qualities, sizes, or varieties in the same lot.
How does the classification of green coffee defects work?
In the coffee industry, a fundamental tool is used to evaluate and classify green coffee defects: the New York Table. This table establishes a precise list of the defects found in green coffee, assigning them a score that reflects their seriousness.
The classification by defects is not only used to determine whether or not to sell the coffee but rather to establish its price. A bag of coffee with more defects will be marketed at a lower price than one without defects.
To classify commercial coffee, it should be assigned a value from 2 to 8 to understand its real quality (NY2, NY3, NY4, NY5, NY6, NY7, NY8). I will give you an example using the New York table:
- A sample of 300 g of raw coffee is taken.
- It is analyzed bean by bean.
- The defective beans are set aside and grouped by type of defect.
- Finally, all are counted and added up.
- The reference table is then consulted, assigning a number from 2 to 8.
| Indicators | Number of defects | Sample (Gr) |
| NY2 | MAX 4 | 300 Gr |
| NY3 | MAX 12 | 300 Gr |
| NY4 | MAX 26 | 300 Gr |
| NY5 | MAX 46 | 300 Gr |
| NY6 | MAX 86 | 300 Gr |
| NY7 | MAX 160 | 300 Gr |
| NY8 | MAX 360 | 300 Gr |
In the classification, according to the New York Table, if up to 4 defects are detected in a 300 g sample, it is assigned the category NY2. In contrast, if up to 160 defects are found in the same 300 g sample, it is assigned the category NY7, and so on.
How are defects in green coffee calculated?
To carry out this classification, another reference table is also used, in which we can find each defect and the score given to it:
| Defect | Score |
| 1 large stone or wood | 5 |
| 1 medium stone or wood | 2 |
| 1 small stone or wood | 1 |
| 1 black bean | 1 |
| 1 dried cherry | 1 |
| 1 large peel | 1 |
| 2 or 3 small shells | 1 |
| 2 to 5 perforated coffee beans | 1 |
| 5 immature coffee beans | 1 |
| 5 green beans | 1 |
| 5 broken coffee beans | 1 |
| 3 shells | 1 |
| 2 coffee beans of parchment | 1 |
| 2 fermented coffee beans | 1 |
In this case, when we find a large piece of wood or stone, we would automatically get a score of 5 defects. On the other hand, if we find 5 immature beans, only 1 point would be assigned to them.
At this point, the roaster must be a selective and trained expert since raw coffee with defects will never allow for obtaining a satisfactory final result in terms of flavor and quality.
What are the defects of green coffee?
Moldy coffee beans – primary
This defect can occur for three reasons: excessive fermentation, too slow drying, or storage in humid environments in the beans.
As expected, these mold-infested beans will bring rancid and unpleasant odors to the cup. Their aromatic characteristics negatively affect the quality and flavor of the final coffee.
Black coffee beans – primary
These beans present bitter notes, unbalanced acidity, and hints of ash and fermentation. These imperfections can cause a delayed harvest, lack of water during maturation, or excessive fermentation.
Insect-infested coffee beans – primary
Pests are common in coffee crops, which deposit their eggs inside the drupe. Once the eggs hatch, the larvae emerge from the fruit.
In the coffee cup, these insect-infested beans can exhibit bitter and tarry notes and a general loss of flavor.
Coffee beans in parchment – secondary
Coffee beans are naturally protected by a layer of resistant skin that surrounds them.
This layer of skin must be eliminated by pulping in the plantation and if this is not done it will burn and generate a bitter and unpleasant taste in the cup of coffee.
Dried cherries – secondary
At this stage, the coffee bean is still inside the coffee cherry. It is necessary to extract it at the plantation before hulling.
If these beans are roasted without being hulled, they will carbonize, which will cause notes of burnt smell and ash in the cup of coffee.
Coffee beans on shell form – secondary
These beans have a distinctive characteristic: they are concave and have a noticeable internal cavity, giving them a peculiar flavor.
Due to their thinness, these beans burn faster in roasting than other beans. As a result, they can contribute notes of bitterness and subtle hints of ash and smoke to the cup of coffee.
White coffee beans – secondary
White beans have a spongy texture created by bacteria after excessive fermentation or in closed places without airflow. The flavor results in the cup will be bitter notes with woody undertones.
Green coffee beans – secondary
When the beans are not harvested at the indicated time or during a drought, the beans do not ripen.
Since they have no color, it is almost impossible to determine their state until they are roasted. In terms of flavor, green beans provide bitterness, astringency, and metallic nuances in the cup.
Broken coffee beans – secondary
Some beans during the hulling or pulping processes break. Broken beans are smaller and roast faster, producing more bitter flavors in the cup.
Malformed coffee beans – secondary
These are beans with abnormal shapes due to changes during their growth. Malformed beans are roasted unevenly, which generates bitter flavors and an astringent sensation in the cup of coffee.
Brown coffee beans – secondary
The skin layer covering the beans is over-fermented. This occurs due to the use of contaminated water. The taste of the coffee will be acidic.
Conclusion
Green coffee defects play a crucial role in the quality and flavor of the final coffee. Each defect, such as mold, malformation, or insect infestation, can negatively impact the coffee experience, resulting in bitter flavors, ash notes, unbalanced acidity, and overall loss of flavor.
