Coffee Roasting Defects – How To Recognize Them?

* This post may contain affiliate links. When you buy through links on my site, I may earn an affiliate commission. *

Coffee roasting defects are a topic that seems to be a bit of a mystery to many drinkers. However, it is easy to avoid those pesky defects and make the most out of your beans with just a little knowledge and understanding. 

This blog post will cover the basics of what you need for roasting coffee beans. We also include some common defects in this process and how to identify them. Let’s dive in!

What’s A Roast Defect, And How Does It Occur?

Roasting beans is a time-consuming procedure. It necessitates mastery of the chemical reactions occurring during this practice and the ability to manage each variable.

It’s tough to get a consistent roast each time, even for the most experienced roasters. This is especially true when roasters are tuning in a roast profile using the latest batch of beans and striving to perfect the balance of body and flavor.

A “roast defect” is the result of human error and not a flaw in green coffee. Roasted coffees can be lost due to over-heating, underheating, or even overheating at various stages. Therefore, causing burnt flavors with an unpleasant taste that will ruin your cup o’ Joe.

These are often found with underdevelopment, meaning that some parts of the bean haven’t had enough time for development. This can lead to flavors reminiscent of hay or corn, among others. It generally happens when roasts happen too quickly and heat is applied before all sugars have been cooked away.

Noticeably, too much time spent roasting those beans can result in an opposite end of the spectrum. The taste is reminiscent of those who enjoy burnt toast and bitter chocolate, with an acidic vinegar-like aftertaste.

What Are Light Roasts, Medium Roasts, Dark Roasts?

Light Roast

Roasted beans are always a gamble, and it’s the roaster who plays that card. This process can produce different flavors. Such as light roasts for those with fewer caffeine needs or dark roast meant only brewed strong.

The coffee bean is often the most valuable part of any blend, and it’s easy to see why. Lightly roasted one will give you a light shade of brown with maybe considerably lighter than most people have ever seen – given how mass-market ones are usually roasted these days.

Medium Roasts/Medium Roasted Beans

When switching from light roasting to medium, the beans add more color and deepen in the shade. You can see a slightly darker shade of brown instead of their lighter counterparts. They’re often roasted longer for an even richer taste with fewer luster notes that many people love.

A first crack is an important event that triggers the release of flavors from beans. The more flavor notes these releases, the better. 

In general, though, it should not sacrifice too much acidity or intrinsic taste to be medium-roasted because many people enjoy strong acids with their dark brews. Yet, others prefer those cleaner tastes without any harsh bitterness whatsoever.

Dark Roasts/Darkly Roasted Beans

The last type is the darkest of roasts. You can find it whether in large markets or traditional ones. It will be darker than your average cup o’ Joe. It’s only fair when they are roasted at their peak darkness level – the most recognized by consumers.

​​Dark roasting is a traditional method used to mask any defects in the coffee bean. The process darkens and develops otherwise present flavor profiles, perfect for commercial markets where appearance matters more than taste.

What Are The Coffee Roasting Defects Signs?

Subjective Roast Defects

This category of roast defect contains: 


One common reason for underdeveloped beans is that we roast them too lightly. This can happen when a roaster sets out with the intention of giving coffee its very best but needs to adjust its profile just slightly so it’s not as grassy or lackluster in taste.


Underdevelopment and overdevelopment are opposites, but they’re not as clear-cut as you might think. Matt Perger from Barista Hustle takes the stance that there’s no such thing as overdevelopment because different roasters have their tastes in development levels for a good cup of Joe to be tasted properly. 

Specialty ones are the best for those who love a darker roast. But if you don’t have experience doing this, it may be hard to know when your bean is finished – so keep an eye on them. They’ll appear dark and oily instead of glowing with white powdery ash, which means they’re ready for grinding or boiling water.


While it might sound like a delicious dessert, baked coffee beans are defects that can be difficult to identify visually. Usually, one will only notice them by tasting the batch, and if they’re there, you’ll get an unpleasant malty taste with papery undertones.

A long, slow roast produces this defect. It’s similar to how we bake cake or bread for a long period at a low temperature. To properly bring about perfect results, the temperature must rise to its peak quickly and stay there for a short period. This period often takes from 15 to 20 minutes.  

Hence, you just have to keep the temperature rising fast and only roast it in that required period.

Objective Roasting Defects

It is amazing how much you can learn about coffee by looking at its defects. When handled correctly, these are some of the most common positive attributes in roasted beans. Coffee does not have any built-in rejections process. So, when there’s an issue with our products, it’s always best to take action quickly before more damage occurs. 


The perfect cup begins with high-quality beans. Unfortunately, scorching can happen when these initially heated surfaces are exposed to a too rapid drum speed and an excessive charge temperature for too long without first slowing down enough or at all in between shots. 

Therefore oil oxidizes more slowly than usual before finally reaching the desired roast level. Most consumers today prefer lighter roasts over darker ones.


Quakers are a unique type of bean that can be hard to identify during hand sorting and green bean inspection. They’re often a result of poor soil conditions limiting sugar or starch development. Still, they may also just have one gene mutation.

Quakers are a lighter shade of grey. You might easily mistake them for white ones. Nonetheless, if they’re not removed from the batch, then you’ll notice papery, and cereal notes with undertones of coffee or tea as well.


There’s a common misconception that scorching happens during the second crack. In reality, it can happen at any point within the process resulting in burn marks on the edges of your coffee beans. Oftentimes, those with too high charge temperatures or an improper setup with their machine tend to face this problem.


This happens when hot metal touches a coffee bean, and it causes charring. Unlike scorching, which usually occurs at the end of roasting due to issues with stuck or held beans against drum wall, facing often comes from problems that happen earlier in production. Sometimes even before you start your first pour-over.


The most common type of roast defect is when a chunk gets thrown out during roasting. This can be caused by uneven pressure distribution. It’s difficult to mitigate in darker roasts, but sometimes lightening them can help. Other times, you just have to put up with the brownies or change your greens.

How Can You Detect Coffee Roasting Defects?

Many physical changes happen with your ingredient then, so it’s important to note them on your quality control sheet. You’ll also want an indication of the rate at which the beans were being roasted in degrees per minute (ROR1 or ROR2). These particular adjustments help make sure everything reaches its peak flavor before ending up on our shelves.

Roasting is more than just a science. It takes dedication and passion for producing high-quality beans that will give you the best cup of Joe possible. Still, without good roasters, these never taste as great. 

Choosing the best profile requires technical know-how and often that intuition that comes with experience. However, recognizing common defects is an important first step. So keep studying, practicing, and learning until you crack the perfect roast profile.


What Is The Difference Between A Light Roast vs A Dark Roast?

Cracks happen when beans are opened by the steam pressure that stems from moisture inside of the beans. The key difference between the two lies in when each roast ends. The former ends soon after you see the first crack, and the latter follows after the second crack.

Why Do People Tip In Coffee Roasting?

People will often tip when their coffee has been heated too quickly on the second crack. Still, heating too quickly does not happen that often.

How Do I Stop My Coffee From Scorching?

The hotter your beans, the quicker they’ll be scorched. Lowering charge temperature will prevent this from happening and give you a superior roast with tastier flavors.

What Happens If You Roast Coffee Too Fast?

It will lack sweetness when roasted too fast and may pucker your face due to the high acidity.

Final Thoughts

Coffee roasting defects are not all bad. They can provide a range of flavors that may be more appealing to some people. As long as you’re aware and understand how roasts work, it’s just an enhancement in flavor. It is important to understand the signs for when these situations occur so that your customers aren’t getting anything they don’t want or need.

Rate this post

Almost 20 years already spent committed to coffee and more than 3 years of experience as a barista at Starbucks. Madelyn Doyle graduated with a Bachelor’s Degree in Nutritional Science from the University of California and finished the Coffee Skills Program at the Specialty Coffee Association (SCA).