Green unroasted coffee beans can exhibit various defects that affect their quality and flavor. These defects can arise during the growing, harvesting, processing, or storage of coffee beans. Identifying these defects is crucial for ensuring the overall quality of the coffee and determining its market value. Here are some common coffee defects and how to identify them:
- Mold and Fungus: Mold and fungus can develop on coffee beans if they are not properly dried or stored in humid conditions. Look for discolored spots or patches on the surface of the beans, which may appear black, green, or white. Moldy beans may also have a musty or earthy odor.
- Insect Damage: Insect damage can occur when coffee beans are infested with pests such as coffee berry borers or coffee cherry moths. Look for small holes or perforations on the surface of the beans, as well as the presence of insect larvae or feces. Infested beans may also exhibit a sour or fermented odor.
- Overripe or Underripe Beans: Overripe or underripe coffee beans can negatively impact the flavor and quality of the coffee. Overripe beans may appear dark brown or black in color and may feel soft or mushy to the touch. Underripe beans may be pale green or yellow in color and may feel hard or brittle.
- Broca or Coffee Berry Borer Damage: Broca, or coffee berry borer, is a beetle that can infest coffee cherries and damage the seeds inside. Look for small holes or tunnels on the surface of the beans, as well as the presence of insect larvae or feces. Infested beans may also exhibit a distinct sour or ferment-like odor.
- Quakers: Quakers are underdeveloped or defective coffee beans that fail to roast properly and often remain pale or light-colored after roasting. Look for beans that are significantly lighter in color than the rest of the batch, with a dull or matte appearance. Quakers may also have a distinctively bitter or sour taste when brewed.
- Foreign Matter: Foreign matter such as sticks, stones, or other debris can sometimes be found mixed in with coffee beans. Look for any non-coffee material present in the batch and remove it manually or with the help of sorting equipment.
- Chipped or Broken Beans: Chipped or broken beans can result from rough handling during harvesting, processing, or transportation. Look for beans that are cracked, chipped, or broken in half, as well as any sharp or jagged edges.
- Inconsistent Size or Shape: Inconsistent size or shape of coffee beans can indicate poor quality or improper processing. Look for beans that vary significantly in size, shape, or color within the same batch, as this may indicate uneven ripening or sorting.
To identify coffee defects, it’s important to carefully inspect and evaluate the appearance, texture, and aroma of the green coffee beans. In addition to visual inspection, cupping (tasting) samples of the coffee can help detect any off-flavors or defects that may affect the overall quality of the brew.
SCA Evaluation of specialty green coffee defects
The Specialty Coffee Association (SCA) has categorized the defects of specialty green coffee into primary and secondary defects.
Primary Defects
Primary defects are more severe and can significantly impact the flavor and quality of the coffee. Examples of primary defects include:
- Full black beans: These beans are rotten or damaged, often due to late harvest, lack of water during fruit ripening, or excessive fermentation.
- Full sour beans: These beans are damaged during processing or storage, often due to over-fermentation or delays between harvesting and pulping.
- Dried cherry beans: These beans are still inside the cherry, which should be removed during processing.
- Fungus damage: Moisture can cause fungus or mold to grow on coffee beans, leading to off-flavors and aromas.
- Foreign matter: This includes stones, sticks, or other non-coffee material that can contaminate the coffee.
- Severe insect damage: Insects can damage coffee cherries in the field or during storage, leading to holes in the bean’s surface.
Secondary Defects
Secondary defects are less severe but can still affect the flavor and quality of the coffee. Examples of secondary defects include:
- Partial black beans: These beans are partially damaged, often due to pests, diseases, or insufficient water during growth.
- Partial sour beans: These beans are partially damaged during processing or storage, often due to over-fermentation or delays between harvesting and pulping.
- Parchment beans: These beans still have a thick, hard film that should be removed during processing.
- Floaters: These beans are lightweight and often defective.
- Immature or unripe cherries: These beans are not fully ripe, which can affect the flavor and quality of the coffee.
- Withered cherries: These beans are dried out and often defective.
- Broken, chipped, or cut beans: These beans are fractured due to mishandling during processing.
- Slight insect damage: Insects can damage coffee beans during storage, leading to small holes in the bean’s surface.
Grading and Classification
The SCA evaluates specialty grade coffee using 350g samples, which must be free from primary defects and contain no more than five secondary defects. The New York classification system assigns a score from 2 to 8 based on the number of defects found in a 300g sample. The score is used to determine the price of the specialty green coffee, with higher scores indicating higher quality and lower prices.
Impact on Flavor
Green coffee defects can significantly impact the flavor and sensory attributes of the coffee. For example, black beans can produce off-flavors with a loss of aroma, while sour beans can create excessively tart and winey flavors. Broken or chipped beans can taste earthy, dirty, or sour, and may roast poorly due to uneven heat transfer. Quakers, which are immature beans, may not contain enough sugars to caramelize during roasting, leading to inconsistent flavor development.
Conclusion
In summary, green coffee defects are physical flaws and imperfections that can affect the quality and flavor of the coffee. The SCA has categorized defects into primary and secondary defects, and provides guidelines for evaluating and grading specialty green coffee. Roasters and coffee professionals use these guidelines to assess the quality of specialty green coffee and determine its potential for roasting and brewing.
