Root Causes of Physical Defects in Green Coffee Beans

by Francesco Dell’Endice, PhD - CEO and Founder of QualySense

The main root causes of physical defects in green coffee beans can be attributed to various factors throughout the coffee production and processing stages. Here are the primary causes of physical defects:

Harvesting Practices: improper harvesting techniques can contribute to physical defects in green coffee beans. Factors such as selective harvesting (choosing only ripe cherries), overripe cherries, or immature cherries being included in the harvest can result in the presence of defects in green coffee. Inconsistent harvesting can lead to variations in ripeness levels, affecting the overall quality of the beans.

Processing Methods: the processing methods employed during post-harvest stages significantly influence the occurrence of physical defects. Inadequate wet or dry processing techniques, improper fermentation, or excessive drying can contribute to defects such as black beans, sour beans, broken beans, or uneven ripening. Insufficient control or monitoring of processing conditions can lead to inconsistent results and defects in green coffee.

Storage Conditions: improper storage conditions can be a major factor in the development of physical defects. Exposure to excessive moisture, high humidity, or improper ventilation can promote mold growth, leading to moldy beans. Inadequate protection against pests and insects can result in insect-damaged beans. Additionally, incorrect temperature control or prolonged storage duration can contribute to the deterioration of coffee beans, resulting in defects.

Transportation and Handling: during transportation and handling processes, rough handling, inadequate packaging, or improper stacking can cause physical damage to the green coffee beans. Vibrations, impacts, or compression can lead to chipped or broken parchment, cracked beans, or other physical defects. Ensuring proper handling and transportation practices are essential to minimize the occurrence of such defects.

Quality Control Measures: a lack of comprehensive quality control measures throughout the coffee production chain can contribute to physical defects. Inadequate sorting, insufficient quality assessments, or lack of attention to detail in defect identification can result in defects going unnoticed or unaddressed. Effective quality control protocols, including meticulous sorting and defect classification, are crucial to reducing the presence of physical defects in green coffee.

Environmental Factors: environmental conditions such as climate, altitude, and soil quality can indirectly influence the occurrence of physical defects. Adverse weather conditions, including excessive rainfall, prolonged drought, or extreme temperature fluctuations, can impact coffee plant health, leading to irregular fruit development and an increased likelihood of defects in the resulting green coffee beans.

Addressing these root causes requires a combination of best practices, quality control measures, and attention to detail at each stage of coffee production, from harvesting to storage and transportation. Implementing proper harvesting techniques, employing appropriate processing methods, maintaining optimal storage conditions, and prioritizing quality control contribute to minimizing physical defects and ensuring the overall quality of green coffee beans.

Green Coffee Defects and Root Causes - Version 2 (Corrected by Norman Mazel, expert in Coffee Quality and Processing)

This is a list of common and non-common physical defects in coffee beans and their root causes.

COMMON DEFECTS

Black Beans

Black beans are a defect characterized by beans that are dark or black. The presence of black beans can indicate issues such as overripe or overly dried cherries, fermentation problems during processing, or fungal infections. Black beans negatively impact the overall quality of the coffee as they can impart undesirable flavors, bitterness, and uneven roasting.

Sour Beans

Sour beans refer to beans with an acidic or sour taste resulting from inadequate fermentation, improper drying, or exposure to moisture. These beans can significantly affect the cup quality, introducing undesirable flavors that are often described as sour, vinegary, or fermented. Proper identification and removal of sour beans are crucial to maintain the desired flavor profile of the coffee.

Insect-Damaged Beans

Insect-damaged beans are a result of infestations by pests such as coffee berry borers, coffee cherry moths, or weevils. These insects can damage the coffee cherries or beans, leading to a decrease in quality. Insect-damaged beans may exhibit physical signs such as boreholes, tunnels, or the presence of insect larvae. Their presence indicates the need for improved pest management practices and serves as a warning sign for potential flavor defects.

Broken Beans

Broken beans refer to coffee beans that are fractured, split, or damaged into smaller pieces. The presence of broken beans is often an indicator of poor handling, excessive drying, or improper processing techniques. These beans can negatively impact the cup quality by influencing brewing consistency and leading to a higher occurrence of undesirable flavors and uneven extraction.

Immature Beans

Immature beans are coffee beans that have not fully developed or reached their optimal ripeness. They are typically smaller, pale in color, and have a higher moisture content compared to mature beans. The presence of immature beans affects the overall cup quality by contributing to astringency, uneven flavor development, and reduced sweetness. Proper sorting and removal of immature beans are crucial to maintain the desired flavor characteristics.

Overripe Beans

Overripe beans are coffee beans that have remained on the tree for an extended period, beyond the optimal stage of ripeness. These beans tend to be larger, dark in color, and may exhibit signs of deterioration such as wrinkling or mold growth. Overripe beans can negatively impact the cup quality by introducing off-flavors, reduced acidity, and diminished complexity.

Chipped or Broken Parchment

Chipped or broken parchment refers to damage or breakage in the outer layer (parchment) of the coffee bean. This defect can occur during processing, transportation, or storage. Chipped or broken parchment can result in increased moisture absorption, leading to mold growth, flavor degradation, and potential contamination.

NON-COMMON DEFECTS

Peaberries

Peaberries are coffee beans that occur as a single, rounded seed within a coffee cherry, rather than the usual two flat-sided beans. While peaberries are not defects in themselves, they are classified separately due to their distinct shape. Peaberries often have a different flavor profile compared to regular coffee beans, characterized by enhanced sweetness and acidity. Their importance lies in their unique market demand and potential to command a premium price.

Quakers

Quakers are underdeveloped or partially roasted beans that fail to achieve the desired brown color during the roasting process. They appear pale or yellowish and can be easily identified in a batch of roasted coffee. Quakers negatively impact cup quality as they tend to have uneven flavor development and can impart a distinct, undesirable taste. Their identification and removal are essential to maintain the desired flavor profile and consistency in the roasted coffee.

Husk

Husk refers to the protective outer covering of the coffee bean, which can remain attached to the bean even after processing. While husk is not typically considered a defect, its presence in green coffee can contribute to higher moisture content, increased susceptibility to mold growth, and potential contamination. Proper removal of husk ensures the purity and quality of the green coffee beans.

Foreign Objects

Foreign objects in green coffee beans include any extraneous material not inherent to the coffee, such as stones, twigs, metal fragments, or other contaminants. These objects can find their way into the coffee during harvesting, processing, or transportation. Foreign objects pose a significant risk to both the quality and safety of the coffee. Their identification and removal are vital to avoid taste defects, and potential damage to equipment during roasting, and ensure compliance with food safety standards.

Mouldy Beans

Mouldy beans are green coffee beans that have been affected by mold growth, usually due to high moisture content or improper storage conditions. Moldy beans pose a risk to the quality and safety of the coffee, as they can introduce off-flavors, mycotoxins, and microbial contamination. The identification and removal of moldy beans are essential to maintain the desired flavor and prevent health hazards.

Stinker Beans

Stinker beans are green coffee beans that emit a foul odor, often resulting from prolonged exposure to excessive moisture or improper fermentation. These beans negatively impact the overall cup quality and can introduce unpleasant, rancid, or fermented flavors. Stinker beans need to be identified and removed to ensure the absence of off-putting odors and flavors in the final cup of coffee.

Waxy Beans

These are buttery, glossy green beans caused by too rapid or excessive mechanical drying and can give a flat taste in the cup after roasting. However, not every country or defect chart considers this issue a defect.

CONCLUSIONS

Each physical defect mentioned above is important to classify because it allows coffee professionals to assess the overall quality and value of green coffee beans. By identifying and categorizing these defects, producers, traders, and buyers can make informed decisions regarding pricing, sorting, and quality improvement measures. Additionally, defect classification helps to maintain consistency, transparency, and consumer confidence in the final cup quality of the coffee, ensuring a positive experience for coffee enthusiasts worldwide.

For more info contact Francesco Dell’Endice at qualysense@ferrum.net.

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