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The common coffee bean defects [Defects in coffee] - 7 common defects found in green coffee beans

HQJ Coffee School will help you gain insights into common defects found in coffee beans. Based on the Specialty Coffee Association's (SCA) green coffee grading standards, this method is considered more advanced and widespread than traditional grading systems in East African countries, such as Kenya. The SCA standards not only provide knowledge about the correlation between coffee bean defects and flavor but also serve as a useful tool in evaluating and selecting high-quality coffee. As a result, you will be equipped with both basic knowledge and advanced skills in distinguishing and selecting coffee correctly.

What are defective coffee beans? What are defects?

In the coffee industry, the term "defective coffee beans" or "defects" refers to imperfections on coffee beans that have the potential to negatively affect the quality and final flavor of the coffee. These defects arise from various causes, which can start from the cultivation stage, harvesting process, processing, and even during storage.

dạng khiếm khuyết thường gặp trên cà phê
Dạng khiếm khuyết thường gặp trên cà phê

Understanding these types of defects not only helps improve the quality of coffee products but is also crucial for ensuring the best tasting experience for consumers.

A brief overview of the classification of defects by the SCA (Specialty Coffee Association)

The Specialty Coffee Association (SCA) has established a detailed and scientific classification system for coffee bean defects. This system is designed to identify and evaluate common defects found in coffee beans. The classification is not only important for industry experts to accurately assess product quality but also supports consumers in understanding the quality of the coffee they choose to purchase.

The SCA classification system includes identifying basic defects such as moldy beans, malformed beans, sunburnt beans, and many others. Each type of defect is identified based on specific criteria, including the shape, color, and other physical characteristics of the coffee beans. In this way, the SCA system not only helps improve the quality of coffee products in the market but also contributes to enhancing the tasting experience for coffee enthusiasts.

7 Common Types of Defects

The 7 most common defects found in green coffee beans. These defects include moldy beans, malformed beans, sunburnt beans, and several others, each with its own distinct impact on coffee quality.

Black beans

Black coffee beans, or black beans, often occur due to overripe harvesting, excessive fermentation during processing, or storage in damp conditions. A fully black coffee bean is classified as a primary defect, while mottled black beans are considered secondary defects. Specifically, each entirely black coffee bean is counted as a primary defect, and every three partially black beans count as one secondary defect. This type of defect can cause unwanted odors in coffee. An effective remedy is proper harvesting and fermentation control.

Black beans – Nhân đen
Black beans

Sour beans

The defect known as "sour beans" or sour-tasting beans occurs due to improper fermentation, often resulting in a brown coloration. Each fully brown bean is counted as a primary defect, while every three partially brown beans count as one secondary defect. To address this, it's necessary to harvest ripe fruits, avoid collecting fallen fruits, and ensure careful post-harvest storage. During processing, it's crucial to control fermentation time, use clean water, and ensure timely drying.

Sour beans – Nhân chua (nâu)
Sour beans

Dried Pod, Cherry

In wet processing, "Dry Pod" or dried husk occurs when the hulling process fails to remove the floating beans at the initial stage. In dry processing, cherries are dried coffee fruits resulting from improper hulling and sorting. Each dried coffee cherry is considered a primary defect, which can lead to bitterness, astringency in coffee, and provide conditions for mold growth. Dried husks also pose a risk of burning during roasting, affecting the quality of the coffee beans.

Dried Pod, Cherry – Vỏ khô, Quả khô
Dried Pod, Cherry

Insect damage

For defects caused by insects, the classification method is as follows: If there are 5 heavily insect-damaged beans (3 or more holes), it's considered a primary defect, and if there are 10 beans with lighter damage (fewer than 3 holes), it's a secondary defect. The main cause is the Coffee Berry Borer beetle, which bores into young coffee fruits. Beans damaged by this pest can result in sour, moldy, or musty flavors if present in high numbers.

Insect damage – Thiệt hại do côn trùng
Insect damage


The defect known as "Floater" occurs due to improper storage or drying processes. These beans are typically lightweight and pale in color due to rapid drying. When undergoing dry processing and prolonged storage, floaters may become more prevalent.

Considered a Secondary Defect: Every 5 floaters = 1 full defect.

Floater/bleached – Nhân nổi (hay nhân trắng)

Floaters can contribute to ferment, grassy, earthy, or moldy odors, but they typically aren't overpowering and can be diluted.

Broken, Chipped

In coffee processing, beans can become broken or chipped due to frictional force during milling. To minimize this, it's essential to adjust milling equipment and sieves carefully. Broken beans typically don't heavily impact flavor, unless present in large quantities.

This defect is classified as a Secondary defect: 5 broken beans = 1 full defect.

Broken, Chipped – Nhân vỡ, sứt mẻ
Broken, Chipped

Beans cracked during wet processing may have a dark red color due to oxidation, which can lead to fermentation, while cracked beans during dry processing are usually clean and not oxidized.


Shells are a type of deformed coffee bean, consisting of two parts, often originating from the initial deformity of the coffee cherry. The outer part resembles a shell or elephant ear, while the inner part is cone-shaped or cylindrical.

Shell – Hạt tai voi

Shells are classified as a Secondary defect, with 5 shell beans equivalent to 1 full defect.

Although they don't affect the flavor, they are prone to burning during the roasting process, which can result in a bitter taste.

Some coffee bean defects you need to know

When researching coffee defects online, you may only find limited information, mainly from the SCA. Roasters often don't share detailed information about these "minor defects." However, thorough research will reveal many flaws in the coffee growing and processing process. To broaden your understanding, HQJ Coffee School will add additional defects that you should eliminate before roasting coffee.

Quaker (Unripe beans)

Quakers are coffee beans that are underripe or unevenly developed, often small and greenish in color. They lack amino acids and sugars, do not participate in the Maillard reaction during roasting, resulting in a pale color and potential bitterness. Specialty coffee typically does not contain Quakers. During harvesting, selecting uniformly ripe coffee cherries helps reduce Quakers. In wet processing, immature beans can be sorted out, but it's more challenging in dry processing, especially in Brazil with mechanized processing methods.

Quaker (Unripe beans) - Nhân non
Quaker (Unripe beans)

Fungus damage

Coffee beans affected by mold, often associated with fungi such as Aspergillus, Penicillium, and Fusarium, can become infected from harvesting to storage. Proper moisture and temperature conditions stimulate fungal growth. Mold-infected beans are identified by powdery spots ranging from yellow to reddish-brown and can spread to other beans.

Fungus damage – Nhân bị mốc
Fungus damage

Withered beans

Coffee cherries shriveled due to drought will produce wrinkled coffee beans, with a grassy, hay-like aroma when brewed. Shriveled beans are smaller, with wrinkles resembling dried grapes. In wet processing, shriveled coffee cherries can be removed using the floatation method due to their buoyancy and lightness. In dry processing, they can be sorted out based on density, small size, and light weight.

Withered beans – Nhân héo
Withered beans

Some notes when selecting coffee beans

The types of defects in coffee that need to be removed before roasting include:

Các lỗi hay gặp khi lấy hạt cà phê
Common errors encountered when selecting coffee beans
  1. Cherry Husks: Commonly found in wet-processed or natural coffee, causing undesirable odors.

  2. Foreign Objects: Such as wood sticks, stones, nails, which can damage grinding machines.

  3. Pulp Fragments: Need to be removed to avoid burning in the roasting machine.

  4. Branches & Organic Debris: Should be removed.

  5. Stones, Pebbles: Can be mixed in with the coffee.


In the coffee processing and roasting process, identifying and removing defects such as cherry husks, foreign objects, and branches is crucial to ensure product quality. Each farm and coffee-producing region faces unique challenges that affect bean quality. Understanding and meticulously addressing these defects not only improves coffee quality but also enhances the tasting experience for consumers.

To further assist our valued readers, HQJ Coffee School encourages you to consider taking the SCA Green Coffee course. This course covers activities related to green coffee processing, selecting the right coffee beans to ensure there are no issues during the roasting process.

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