Spotting 10 Green Coffee Defects: From Full Black to Insect Damage


Green coffee defects are blemishes that can occur on coffee beans due to a variety of factors. These defects can be caused by physical, mechanical, biological, chemical and environmental anomalies. All of these have an impact on cup quality when left unchecked!

Knowing about these different types of defects is important for roasters as it allows them to identify them during the production process and take steps to minimize their impact on cup quality.

With this knowledge under your belt, you will ensure your customers get only the highest quality cups every time! Let’s take a look at green coffee defects and how they affect cup quality.

The 4 major types of coffee defects

Coffee lovers everywhere can relate to the importance of high quality coffee beans. For centuries, coffee has been enjoyed all over the world and its flavor depends largely on the quality of the beans used. Unfortunately, coffee beans can sometimes suffer from defects which reduce their flavor and aroma.

To ensure that you get the best cup of coffee every time, it’s important to be aware of the four major types of coffee defects: physical defects, mechanical defects, biological defects, and chemical defects.

By understanding these four major types of coffee defects and their causes you will have an increased appreciation for quality roasted coffee beans. Each type requires careful attention during production to guarantee superior results that make every cup memorable.

A little bit of knowledge on this topic can help you distinguish between great tasting cup of joe and a lackluster one. After all, no one deserves to settle for substandard flavors or aromas in their daily cup!

1. Physical Defects in Coffee Beans

Physical defects are blemishes that occur on the bean’s surface due to handling or storage issues. These blemishes can range from broken pieces of the bean to discoloration or spots, to foreign material such as dust or insects.

Roasters must be able to spot these physical anomalies so they can determine if they need to take further action in order to maximize cup quality from defect-affected coffees.

2. Mechanical Defects in Coffee Beans

Mechanical defects are caused by mechanical forces such as grinding, crushing, or splitting of the beans during harvesting or processing. These blemishes can lead to improper extraction during brewing, resulting in an undesirably weak cup profile with off flavors and aromas.

Roasters must be aware of these potential mechanical issues so they can adjust their roast profiles accordingly.

3. Biological Defects in Coffee Beans

Biological defects refer to any damage caused by pests, fungi, or bacteria while the bean is still growing on the tree or during post-harvest storage and handling. These include moldy beans and insect damage which can impair flavor and cause off-flavors such as mustiness or sourness if not identified and removed prior to roasting.

Roasters should inspect each batch of green beans carefully for any signs of the biological defect before roasting commences.

4. Chemical Defects in Coffee Beans

Chemical defects are caused when certain chemicals come into contact with coffee beans either through contact with pesticide residues or poor storage conditions (e.g., high temperatures).

Chemical damages can lead to taints such as bitterness and astringency that will affect the overall flavor profile of a given batch of roasted beans if not identified early enough in the process.

To avoid this issue, roasters should always ensure their green beans have been stored properly prior to roasting them.

Primary and Secondary Coffee defects by the Specialty Coffee Association? 

As specialty coffee continues to gain popularity, it is critical that consumers understand the different defects that can occur in green coffee. The Specialty Coffee Association has identified two types of defects in green coffee beans: Primary and Secondary.

When selecting green coffee beans for roasting and brewing, it is important to keep an eye out for both primary and secondary defects outlined by the Specialty Coffee Association.

While most secondary defects won’t impact the taste of your cup directly, too many may still cause you to reject a batch due to its lack of marketability. On the other hand, any primary defect should always be rejected as it will have an immediate negative impact on your cup’s flavor profile!

Let’s take a look at what these are, and how they affect the quality of your cup of joe.

Primary Defects in Green Coffee

Primary defects are those which cause an overall degradation of the bean’s physical characteristics. These include Full Black, Full Sour, Dried Cherry, Fungus Damage, Foreign Matter, Severe Insect Damage, Pod/Cherry Stones (Large and Medium), Sticks (Large and Medium) All of these primary defects will hurt the flavor of your coffee.

Secondary Defects in Green Coffee

Secondary defects are those which will not have an effect on the flavor of your coffee. These include Partial Black, Partial Sour Parchment Floater Immature or Unripe Cherries, Withered Cherries Broken Chipped or Cut Beans Slight Insect Damage Parchment Hull/Husk Broken/Chipped Partial Sour Floater Shell Small Stones Small Sticks Water Damage.

While these secondary defects won’t affect your cup’s taste directly, too many may still be grounds for rejecting a batch since they may negatively affect its marketability.

The most common coffee defects

When it comes to coffee, it’s not just about the taste and aroma – it’s also about the quality of beans to make sure you get the best possible cup. Unfortunately, there are some common defects that can occur in coffee beans, which can affect both the taste and quality of your cup.

Such defects include full black and partial black beans, full sour and partial sour beans, broken or chipped beans, insect-damaged beans, fungus-damaged or mouldy coffee beans, frost damaged coffee beans, un-hulled coffee beans , quaker beans, floater beans, and old crop coffee beans. Each of these defects can have an impact on your brew depending on severity levels.

1. Full Black and Partial Black

Coffee beans come in different shapes, sizes, and colors. Some are green, some are brown, and some are black. But what about full black or partial black coffee beans?

Full black/partial black coffee beans can have a major impact on your cup of joe, from flavor to aroma to overall satisfaction level. While it is possible to enjoy a good cup of coffee with partial black, full black coffee beans are not.

It is important to understand why they occur in order to avoid them in future harvests and processing cycles. By understanding how full black/partial black beans form and their effects on taste and aroma, you can better identify them in order to ensure every sip is one worth savoring!

What are Full Black/Partial Black Coffee Beans?

Full black/partial black coffee beans occur when a cherry has not been processed correctly. This usually happens when there is an issue during the growth process such as:

  • Pest or disease attack;
  • Insufficient water during growth.
  • Immature beans.
  • Over-ripe cherries.
  • Over-fermentation.
  • Not enough water during cherry development.

When these conditions occur, the cherries turn a dark color—sometimes even full black—and the resulting beans can also be affected when they’re dried and milled.

Full black coffee defects are the most severe type of defects that can occur in roasted coffee beans. Full black coffee beans are characterized by an even distribution of color across the surface of each bean.

Partial black coffee defects are less severe than their full black counterparts. Partial blacks have uneven coloration on some surfaces. Often a combination of light and dark colors (e.g., white spots on otherwise dark brown beans).

The Impact of Full Black/Partial Black Coffee Beans on Taste and Aroma

When you brew a cup of coffee with full black/partial black coffee beans, you may notice that it lacks flavor or has an off-flavor compared to other coffees. This is because the defect within the bean affects its flavor compounds. Additionally, you may also find that your cup of coffee lacks aroma due to the same defect.

2. Full Sour & Partial Sour

Full sour beans are defined as beans that have been over-fermented due to being left in the fermentation tank for too long. These beans have a distinct yellowish color with discolorations on the surface which indicate they have gone beyond the peak point of fermentation.

Partial sour beans also show signs of over-fermentation but usually not as severe as with fully-soured beans. The discolorations on these beans tend to be more subtle than those found on full sour beans.

Causes of Full Sour & Partial Sour Beans

The main cause of both full and partial sour bean defects is over-fermentation due to delays between harvesting and pulping, contaminated fermentation tanks or water used during processing, or storing green coffee with a too high moisture content which can lead to mold growth or bacterial activity in the tank.

All of these factors contribute to an increase in acidity levels in the coffee which can result in either full or partial sour bean defects.

Characteristics of These Defects

Full sour and partial sour bean defects both have distinct characteristics that enable them to be identified easily by farmers, processors, and roasters alike. The visual appearance will be yellowish with discolorations on the surface of the bean while they also often emit a strong acidic smell when wetted or roasted indicating that something has gone wrong during processing.

Additionally, both types of defective beans will often impart an unpleasant taste or flavor profile when brewed which is another indicator that something has gone awry during processing.

Impact on Coffee Quality & Flavor Profile

Defective coffee beans such as full sour and partial sours can drastically reduce the quality and flavor profile of any specialty grade coffees being produced leading to potentially negative impacts on price point if it does not meet minimum standards set by specialty grade certifying bodies such as SCA (Specialty Coffee Association).

As such, it is important for producers to understand what causes these types of defects so they can work towards avoiding them together during production processes.

Tips For Avoiding Full Sour & Partial Sour Beans

When it comes to avoiding full sour and partial sours there are several tips that producers should follow including properly storing green coffee so that moisture levels remain consistent throughout storage periods:

  • Monitoring fermentation time & temperature closely during processing.
  • Utilizing proper hygiene techniques before fermenting green coffee.
  • Ensuring any water used for fermenting is free from contamination prior to adding green coffee into tanks for processing purposes etc…

Following these tips will help producers reduce their chances of encountering this type of defect significantly thus improving overall quality control procedures when dealing with specialty grade coffees etc…

3. Broken, Chipped, and Cut Coffee Beans

Broken, chipped and cut coffee beans refer to defects that occur when the green coffee seed inside the cherry is damaged during processing or storage.

These defects can be caused by mechanical handling or improper storage conditions such as temperature extremes or humidity levels being too high or low. The taste of these defects can vary from mild to unpleasant depending on their size, shape, coloration and degree of damage.

Depulping Machines: How They Cause Broken Coffee Defects

The depulping process is one of the most important steps in transforming raw coffee cherries into green coffee seeds (beans). During this process, the fruit is removed from around the bean so that it can be processed into roasted coffee.

However, if the beans are not handled properly during this process they can become cracked or split which causes this secondary defect. This type of damage reduces bean size as well as flavor quality because it affects the internal structure of the bean making it more susceptible to moisture loss during roasting.

4. Insect-Damaged Beans

Coffee berry borers (Hypothenemus hampei) are a type of beetle that attack coffee cherries while they’re still on the tree in the field.

These insects feed on both ripe and unripe cherries resulting in puncture wounds in both cases which causes secondary defects in coffee beans due to either physical damage or infestation with larvae.

Insect-damaged beans have an unpleasant taste due to fermentation caused by egg laying female beetles as well as excretions from larvae feeding on the green seed inside the cherry.

5. Fungus-Damaged or Mouldy Coffee Beans

Fungus-damaged or mouldy coffee beans are caused by excess moisture and humidity when storing your beans. This is a common problem if you live in an area with high levels of humidity or if you store your beans improperly.

The symptoms include discoloration (green or yellow spots on the bean) as well as a musty smell and taste once brewed.

The solution is simple, though: store your beans in an air-tight container away from any moisture sources.

6. Frost Damaged Coffee Beans

Frost damaged coffee beans occur when frozen temperatures come into contact with the beans for too long of a period. This can happen if you don’t properly store your beans after purchasing them from a store that has freezers or refrigerators on site.

Symptoms of frost damaged coffee include discolored patches on the bean surface as well as an off-putting aroma once brewed.

To avoid this issue, always make sure to buy any coffee stored near freezer/fridge units only after they have been brought back up to room temperature before storing in an air-tight container at home.

7. Unhulled Coffee Beans

Unhulled coffee beans are actually just immature green coffee cherries that haven’t completely ripened yet before being harvested.

Symptoms of unhulled beans include a very sour taste and acidic flavor once brewed, which can be quite unpleasant!

The best solution here is simply avoiding such immature cherries altogether – always check labels carefully before buying to make sure you’re getting fully ripened cherries every time!

8. Quaker Beans

Quaker beans are unripe or incompletely roasted coffee beans. In the roasting process, the peaberry inside the bean is supposed to expand and fill up the cavity in which it sits. When this doesn’t happen properly, it is referred to as a “quaker” bean since it remains partially flat like an undercooked pancake.

These inferior beans produce a sour or unpleasant taste in your cup of joe and should be avoided at all costs. To identify quaker beans, look for uneven shapes or sizes compared with other coffee beans from the same batch.

9. Floater Beans

Floater beans are defective coffee cherries that float on water during sorting due to their lower density caused by hollow centers or low moisture content.

They are usually removed from the batch during washing stations since they contain such little flavor or aroma when brewed.

You can identify floaters by their light color and lack of shine compared to other healthy coffee cherries. Floaters also have an unusual shape that sets them apart from regular coffee cherries; they have been likened to potatoes due to their irregular size and shape!

10. Old Coffee Beans Crop

Old coffee crops refer to green coffees that were harvested more than six months prior to when they were purchased and roasted for consumption.

These coffees often have a musty smell and taste stale since they have been sitting for so long without being processed into drinkable coffee beverages.

In order to identify old/past crop coffees, check out their origin date; if it was harvested more than six months ago, then it is best to avoid these kinds of beans altogether as they may have lost some of their flavor characteristics over time due to overexposure (or simply because they weren’t stored correctly).

Exploring Roasted and Unroasted Coffee Beans

Deciding between roasted and unroasted coffee beans is like choosing between bold and subtle flavors. Roasted beans bring out a rich taste of chocolate, caramel, and nuttiness, along with a smoky aroma.

On the other hand, unroasted beans offer a gentler flavor with hints of fruitiness and tanginess. It all depends on the kind of coffee adventure you’re seeking. Learn more about these flavor-packed beans in our guide on Roasted Vs. Unroasted Coffee Beans.

Unraveling the complexities of green coffee defects? Enhance your expertise by diving into the Origin Differences: Coffee Cupping Guide. Discover how origin plays a pivotal role in determining coffee quality.

About The Authors

  • Betty Pritchard

    From Madison, Wisconsin, Betty is a coffee aficionado turned writer. A UC Davis graduate in Sensory Analysis with a Food Science certification, she’s a Good Food Award recipient. Hosting a podcast and crafting coffee art, her journey spans from college vending to elite cafés. A pour-over devotee, Betty’s expertise and passion make her essential to Coffeescan’s team.

  • Donald Anderer

    Denver-born Donald blends mountain vibes with coffee artistry. A Rhode Island School of Design alum, he paints with coffee and captures its essence with certified food photography skills. Favored brew? The intense Ristretto. Coffeescan’s artistic soul.

  • Fikru Assefa

    Born in Sidamo, Ethiopia, Fikru combines a Harvard History degree with certifications in Coffee Culture. Adept in traditional Ethiopian coffee ceremonies and a lover of Drip Coffee, his expertise offers readers a deep dive into coffee’s rich tapestry. Join him on a caffeinated journey at Coffeescan.com.

  • Ronald Naughton

    From San Diego, Ronald is the Senior Coffee Editor at Coffeescan.com. His journey began in a city café, leading to a Coffee Science degree from UC Davis and a professional brewing certification. Recognized by the Food Bloggers Awards, he claims to identify a bean’s altitude by taste. Affogato enthusiast and coffee connoisseur, Ronald ensures Coffeescan’s content is rich and precise.

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