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Are there actually nasty defects in your roasted coffee beans?

Yup, a popcorn. Definitely a popcorn. What else is hanging out in your coffee?

Defects and foreign matter are not uncommon in coffee. They can range from harmless popcorn to crazy things like staplers and nails. More commonly though, they tend to just be some inconsistencies in the coffee beans’ roast. Let’s explore some of the common defects found in coffee.

Foreign Matter

Starting with the crazy stuff, there’s been numerous times that we’ve found popcorn in our coffee. This shouldn’t be surprising as some of the farmers also plant other crops such as corn, avocados and bananas as sustenance crops. So, it is understandable that something small like corn can be accidentally included in the coffee crops.

Popcorn in Coffee

More concerning though, are foreign matter like metal staplers, nails and rocks. These are the ones that really worry us since they can pose a real risk to doing some harm. Majority of the time, these are not an issue because they are pre-sorted and removed at origin. Roasteries also keep an eye out during and after roasting to ensure that they are sorted from the final packed coffee.

However, there are times when a small rock or other matter might still slip through the cracks. If you ever experience this, do not hesitate to contact the roaster/retailer you bought the coffee from. I am sure they would have zero qualms replacing the bag of coffee for you.

Quakers (under / over-ripecoffee)

On to some less scary defects. As you know, coffee is a fruit, so it is inevitable that the coffee cherry is not always picked when it is fully ripe, even if the farm employs hand-picking. This is especially true with commodity coffee which sometimes employ strip picking or even mechanical harvesters which strip down the entire tree. (Strip picking involves taking hold of a branch of the coffee tree and using a single motion to pull off all of the coffee cherry on the branch at once)

Coffee Quakers

Since the coffee cherries don’t all ripen at the same rate, there are unripe and overripe cherries that get added into the mix of coffees. This is much less common in specialty coffee where most cherries are hand-picked and sorted for ripeness. However, as with most things, human error does occur and some underripe/overripe cherries get included into the mix.

These coffees absorb heat during the roast differently. The end result is either a coffee bean that is distinctly lighter or darker than intended. Although, there have been some farmers experimenting with new techniques to blend coffees with different ripeness together to create unique taste profiles. Check out our Colombia Finca Zacatin for an example.


Tipping is a very common occurrence in roasted coffees. It is usually characterised by a small charred/burnt mark close to the tip of the bean. This occurs as the tip of the bean is generally the weakest part of the coffee and acts as a release valve when heat is applied to the coffee.

Coffee Tipping defect

Since there is a large concentration of heat escaping the bean through the tip, it tends to overheat and burn the area around the tip of the coffee. Now although this is considered a defect, there are different severities to tipping. Most of the time, they are generally mild and not detectable in the cup. It is only the more severe cases which imparts a burnt taste into the brewed coffee.

Shells / Chipped coffees

Shells are a natural occurrence in coffee. They do not have a major impact on the taste of the coffee and are mostly a visual defect. Chipped coffees on the other hand can be a result of mechanical de-pulpers or poor machine calibration in the dry mill that damages the coffees. This can have a slight impact on the resulting acidity and aromatics of the coffee.

The real problem from these defects is the uneven roasting and heat absorption compared to physically un-damaged coffee beans. The shells and chipped coffee beans have a much higher tendency to burn and over-roast due to their thinner and weaker structures.

Scorched / Charred

Scorched Charred coffee defect

These defects are easily identifiable through patches or spots of burnt marks on the coffee bean. It generally occurs when the roaster is too hot or aggressive in heat application. Although it might not be a defect for some roasters who are gunning for very dark roasts, it is generally undesirable with most specialty coffee roasters.


Craters are a roast defect caused by aggressive heat application and generally occurs in darker roasts. The bean explodes from the pressure build-up on its way to 2nd crack and leaves a charred crater on the bean’s surface.

Coffee Crater Defect

Congratulations! You are now an expert on roasted coffee defects. So, the next time you spot something funny in your beans, you’ll know exactly what it is!

But of course, as with all things coffee, these are just the tip of the iceberg. There are still many defects present in green coffee and are invisible to the naked eye. These can persist in the roasted coffee and present themselves as off/foul flavours.

If you’d like to learn more about green coffee and how to craft them into perfectly roasted coffee beans ripe for brewing, check out our Ultimate Roasting Course here. Alternatively, we also have some awesome roasted coffees for you to enjoy at our online shop. Check it out!

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