Coffee Defect Bean Classification Standards: What Are Common Green Coffee Defect Beans and Should You Sort Beans Before Brewing?

Understanding Coffee Bean Defects: Separating Fact from Fiction

Since FrontStreet Coffee's main business is selling beans, in addition to questions about coffee brewing and preparation, our backend frequently receives feedback about bean-related issues. For example, concerns about defective beans. Some customers bring photos to FrontStreet Coffee, asking whether the beans in the pictures are defective. However, among all the photos FrontStreet Coffee has reviewed, nearly 90% of the beans are not actually defective.

The reason so many people frequently misunderstand this issue is that there are certain misconceptions about what constitutes a defective bean. For instance, some believe that roasted coffee beans should all look similar to industrial products—round, full, and smooth. Of course, a more significant reason is that most people haven't had formal exposure to defective beans. Because information is so readily available today, we can see a lot of information about coffee beans online, including information about defective beans. Such as insect-damaged beans, moldy beans that have developed fungus, underdeveloped quaker beans, and so on. Although these are often accompanied by corresponding pictures, since most people haven't actually seen the physical objects, they can only remember some simple definitions and the names of defective beans.

In reality, defective beans are primarily concentrated at the green bean stage, and for most consumers, the opportunity to encounter them is extremely small. One reason is that most coffee-producing regions screen for defective beans when exporting coffee beans, as the grading standards in those countries use defect rates as a classification criterion. When the defect rate of beans is lower, the grade is higher, and higher grades can be sold at higher prices. To sell at better prices, green bean merchants specifically screen out defective beans from coffee beans. Roasters also prioritize purchasing high-grade coffee beans to ensure quality and save screening time. So by the time these beans reach them, they've already undergone one screening, and the proportion of defects in the green beans themselves is already very small.

Even if a small number remain, most defective beans would severely negatively impact the entire coffee experience, and no roaster would risk damaging their reputation for convenience. Therefore, before roasting, most roasters screen the green coffee beans to remove defective ones, ensuring their products maintain excellent quality.

However, some defective beans that are difficult to capture before roasting, such as white-centered beans, as well as defects that occur during the roasting process, are unavoidable. In such cases, FrontStreet Coffee's approach is to conduct a manual secondary screening after the coffee beans have completed roasting, removing these defects that affect the experience. Subsequently, we weigh and package them before sending them to buyers. Therefore, we can understand that after this entire process, consumers have very little opportunity to encounter what the industry considers major defective beans.

What we need to know is that a bag of beans is not entirely free of defective beans; it's just that those that severely affect taste are unlikely to appear (for most businesses). More commonly, there are broken beans that have cracked during transportation due to collisions. They are merely incomplete and do not affect the overall taste of the coffee. (These are the beans with irregular cracks.) So next, FrontStreet Coffee will share some beans that are often easily mistaken as defects but actually aren't!

1. Wrinkled Beans with Obvious Black Spots/Stripes

This type of bean is most often considered defective by people because its surface is covered in wrinkles and has obvious black spots/stripes, which greatly differs from the smooth, round appearance of coffee beans in some classic pictures, so they are often mistaken for insect-damaged or moldy defects.

In fact, these beans are not defective at all and may even have excellent flavor characteristics! This appearance is mainly caused by two situations: first, light roasting (the most important factor), and second, beans grown at high altitudes! Coffee beans shrink during roasting as moisture evaporates, forming wrinkles and stripes on the surface. As roasting time increases, these wrinkles gradually expand as the bean body begins to expand, and the bean surface gradually becomes smoother. However, to better express the inherent flavors of the beans, we often need to remove them from the roaster before excessive reactions occur, stopping the roasting process. These wrinkles remain on the beans because they don't have time to expand before coming out of the roaster, resulting in the somewhat "unattractive" appearance we see.

2. Coffee Beans with Large Cracks

Some beans have cracks in addition to the central "crack," and this type of bean is also mistakenly considered defective by most people. But actually, these beans are perfectly normal!

During roasting, the moisture contained in the beans converts to steam due to heating. Initially, this steam is trapped inside the bean body by the sturdy exterior and cannot escape. As steam continues to accumulate, the bean body gradually cannot withstand the increasing pressure, and then, BOOM! The steam escapes as the bean body ruptures, accompanied by a loud sound, announcing that the bean has roasted to maturity—this is what we commonly call "first crack." Some denser beans, being too hard, accumulate too much steam and have greater force when they rupture, creating an extreme appearance. But in reality, they are merely unattractive and taste no different from other beans.

3. White-Centered Beans?

As FrontStreet Coffee mentioned earlier, among coffee bean defects, there's one called "white-centered beans" (quakers). They occur because coffee farmers pick them before they are fully ripe, resulting in green beans with less sugar and other substances, making them tasteless after roasting.

Since they don't differ much from other coffee beans at the green stage, they can easily mix with other beans and get roasted together. Eventually, due to insufficient sugar and other substances, they don't undergo excessive reactions and appear significantly lighter in color than other beans when they come out of the roaster. But because of this significant difference, quaker beans are defects that can be easily identified by workers after roasting. Additionally, since the current mainstream coffee harvesting method is manual picking of fully red cherries, situations with large quantities of white-centered beans are rare. Therefore, overall, it's very difficult for consumers to see white-centered beans in the beans they purchase. Nevertheless, many friends still bring photos of suspected white-centered beans to FrontStreet Coffee because they are lighter in color compared to other beans in the same bag.

FrontStreet Coffee has summarized the beans purchased by these friends who raised questions and found that these beans suspected of containing large quantities of "white-centered beans" all come from anaerobic or honey-processed beans. So the answer is quite clear. Because when beans undergo these processing methods, large amounts of sugar adhere to the bean surface. Since the amount of sugar attached to each bean varies, during the subsequent roasting process, under caramelization reactions, beans with more surface sugar will appear darker, while those with less sugar will be lighter. This results in beans of two different colors from the same roast batch, leading to misunderstandings among friends.

In summary, we can understand that some beans just look special, but in reality, they truly are not defective beans~~

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