Green coffee defects are critical factors in determining the quality of roasted coffee. They can affect both the sensory attributes (flavor, aroma) and the visual appeal of coffee. Identifying, removing, and avoiding these defects is vital for producing premium coffee.
What are Green Coffee defects? These are a type of coffee that exhibits unnatural characteristics and poor quality due to errors that occurred during cultivation, harvesting, processing stages. These processes are considered as critical points in the coffee process, in other words, if the coffee bean deteriorates in one of these stages, the defects caused cannot be reverted to good quality beans in the following stages. Through the application of good agricultural and manufacturing practices and systematic controls in the production stages, defects can be prevented and the consistency and quality of the coffee can be improved. When referring to the term “Defect” the Specialty Coffee Association (SCA) also includes unwanted foreign objects that may appear in coffee, such as rocks, branches, and insects. These defects can significantly impact the quality and taste of the cup.
After Hulling, a bulk sample is acquired, and before roasting, there are factors to consider which include the bean moisture content, water activity, density, screen size and defect count.
In this article, i am going to discuss various defects in green coffee and how each impacts the quality of the final cup. SCA has published a set of documents on these coffee defects to unify and systematize the standards for screening and evaluating the quality of Specialty Coffee.
SCA has only released publications dedicated to Arabica coffee beans, without official guidelines applying to Robusta or Liberica. However, currently, producers or roasters implicitly understand and use the same standards for all coffee beans they produce.
Categories
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Primary defects include: full black, full sour, Severe insect damaged, pod/Dried cherry, large stones, medium stones, large sticks, medium sticks.
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Secondary defects include: Partial black, parchment, hull/husk, broken/chipped, slight insect damaged, Immature/Unripe, Withered, partial sour, floater, shell, small stones, small sticks
Common coffee defects and how they affect the quality of coffee
Full Black & Partial Black Beans-Full black beans is a primary defect, while partial black is a secondary one. The beans are brown or black, shriveled, and with the crack too open. Causes include over fermentation, over-ripe cherries, and not enough water during cherry development.
Effects that occur in the cup: fermented flavor, acetic cup acid, rancid/earthy, musty/wet, sour, or phenolic. In addition, another problem that is generated is the risk of ochratoxin. These defects can be avoided by harvesting only ripe fruits from coffee trees, thus avoiding conditions for over-fermentation during processing at the plantation.
Full Sour & Partial Sour Beans-Full sour beans are a primary defect, while partial sour is a secondary defect. They are a light to dark brown. These defects are caused by too long a wait between picking and depulping, an overly long fermentation process, or storing the beans while they have too high a moisture content.
Effects that occur in the cup: sour, fermented, acetic acid, depending on the degree of fermentation of the bean. Other problems: Affects the appearance of the green bean.
In the farm harvest exclusively ripe cherries (avoiding overripe cherries), do not pick fallen cherries, and do not grow coffee in low-altitude areas close to lakes, rivers, or dams to avoid fermented sour beans.
In processing ,it can be avoided by
a) Pulping cherries right after picking, avoiding long storage;
b) Controlling fermentation time in fully washed coffees;
c) Avoiding contaminated water during washing;
d) Timing the drying process to avoid interruptions;
e) Using color sorters or manual sorters to eliminate sour beans after removing the parchment.
Severe or Partial Insect Damage-Another secondary defect, this is caused by coffee pests: the coffee beetle borer, the white stem borer, the coffee bean weevil, and so on. Coffees damaged by the coffee beetle borer ( la broca) tend to be sour and earthy. Another insect is the Antestia bug: These small, shield-shaped, dark brown insects create holes in the coffee cherry’s skin, allowing airborne bacteria to enter which usually causes the potato defect in coffee.
Other effects that occur in the cup: It impacts the appearance of roasted coffee beans, and can generate rancid/earthy, sour, or musty/wet flavors, especially if present in large quantities. Among its risks is ochratoxin, which affects the appearance of green and roasted beans.
The best way to avoid coffee damaged by CBB in the farm is, after detailed inspection, to eradicate the conditions that favor its spread. Chemical spraying is one option, but its limited effect has led to a focus on integrated pest management techniques (such as certain specially designed fungi: Beauveria bassiana) and the use of African wasps (C. stephanoderis); since these beetles reproduce inside the seed, it is necessary to collect all the cherries that fall to the ground to eliminate their proliferation conditions. In addition, the ripe cherry pulp can carry the insect, so they should be kept at a reasonable distance from the coffee trees until composting has been completed. It is unreasonable to expect pickers to distinguish between healthy cherries and cherries damaged by insects since the damage caused is usually visible on the inside without close examination.
In processing insect-damaged coffee will become apparent when the parchment is removed. At this stage, density graders can remove most of the brocaded coffee. In case of severe infestation, coffees should be hand sorted. A massive CBB infestation can be catastrophic for farmers, rendering much of the crop unfit for export.
Some of the Key Practices Farmers should follow to Ensure High-Quality Green Coffee.
To avoid defects in green coffee and ensure high-quality beans, farmers need to implement key practices during cultivation and harvesting.
Proper farm management involves maintaining soil health with appropriate nutrition and acidity, ensuring optimal watering to prevent stress, and managing shade to protect coffee trees from excessive sunlight. Pest and disease control through Integrated Pest Management (IPM) is crucial. Farmers should monitor for common threats and use resistant coffee varieties, while keeping the farm clean to reduce pests.
Regular pruning of coffee trees allows for better airflow and sunlight, which decreases disease risk and promotes even cherry ripening. Farmers should also consider replanting old trees that produce lower-quality beans. Harvesting should be selective, prioritizing ripe cherries, ideally through handpicking to avoid including under-ripe or overripe beans.
After harvesting, it’s important to process cherries quickly and wash them to prevent fermentation. Drying requires attention to prevent mold and ensure proper moisture levels. Storage should occur in a cool, dry environment, and transport containers must be clean to avoid contamination. Continuous quality checks and traceability systems will help maintain high standards from farm to market.
Correctly following these practices enhances product quality and ensures a higher market value and returns for your coffee as a farmer.