The 6 Coffee Roasting Defects (Important Facts to Know)

Last Updated on January 30, 2022 by John Moretti

Have you ever wondered why your coffee tastes slightly off-putting at times despite the error-free brewing and roasting process? This might be due to coffee roasting defects. 

Encapsulating an ideal taste profile is always a result of some practices followed by the amalgamation of the right flavors. However, due to the fickleness of the coffee beans, not every batch you roast will come out to be consistent. 

In some cases, flavors, such as bitterness, may overpower the natural undertones of your beans, which is something that you don’t want. 

This article will guide you on how to identify certain roasting defects and also mention ways to avoid them. 

Coffee Roasting Defects

A coffee roasting defect is usually a derivative of human error while roasting that results in a bitter and papery taste. These defects can be further bifurcated depending on whether the beans are under or overdeveloped. To avoid them, you must monitor your coffee on a regular basis and keep the rate of rise in check. Preheating your equipment along with taking notes frequently is also effective. 

The 6 Types Of Roasting Defects 

Prior to diving into the types of roast defects, it is essential for you to understand the reason behind their occurrences. Unlike bean defects, which have to do with the quality of your beans, a roast defect is typically caused by human error. 

If a roaster fails to control variables like temperature, air, or smoke during the roasting process, then the roast may end up with these defects. Whether you add excessive heat to your batch or miss out on adding enough heat, both cases can give rise to plenty of imperfections in taste. 

In the case of underdeveloped beans, a grassy texture along with a raw taste is left in the beans. This occurrence is likely if the roast is completed in a rush. The sugars do not get enough time to develop, which causes flavor hints of corn, hay, and lentils. 

On the contrary, if you roast the beans for too long, it may result in loss of acidity and caramelization. The flavors witnessed in overdeveloped beans are charcoal-like and burnt. Now, let us further categorize these defects. 

1. Baking

Coffee Roasting Defects

A majority of people encounter this defect when their beans are overdeveloped. In some cases, it occurs due to sudden changes in the roasting temperature. Let’s say that you roast the beans for too long before they crack and there is a sudden decline in the temperature in the middle of the process. This causes the baking defect and you end up with a papery flavor in your final brew. 

Now, as you might know, the beans start breaking around a temperature of 385℉. If your beans are taking too long to crack, owing to the lack of/excess moisture, then the prolonged crackling effect may split beans down the middle when the water evaporates. 

2. Tipping

This refers to the scorch marks which are usually seen on the tips of coffee beans. You can identify this effect by looking for a black mark at both ends of your coffee bean. This usually arises due to rapid roasting. 

However, tipping doesn’t always affect the flavor too much as it doesn’t affect the whole bean. Tipping adds a slightly smoky and oily flavor to a beverage. 

3. Scorching


Rapid temperature hikes lead to the scorching of the beans. Much like the name suggests, this process ends up giving the whole bean a black charcoal briquette-like finish due to excessive carbon dioxide deposits. 

High-quality roasteries usually pull out all the scorched beans before packaging their product. Hence, it is quite rare to find them in on-shelve coffee packs. However, if you go for cheaper brands, you may end up with a few. 

Scorching usually tips the taste towards a bitter side. If you are a home roaster, then you should look out for these black beans to improve your quality control. 

4. Facing

Facing can be simply termed as uneven scorching. This happens if a particular bean gets stuck on the metal plate for too long. This is the reason I often advise you to keep stirring your beans when using methods like an oven or frying pan. 

One side of the bean is usually perfect while the other side ends up black due to the prolonged exposure to heat. 

5. Chipping

Cracking is a pressure-intensive task. Some coffee beans cannot withstand the pressure and end up breaking down during roasting. This defect is more common during darker roasts. As opposed to light or medium roasts, darker stages take more time and require two cracking phases. 

These chipped beans have a black hole that can be easily spotted. However, you shouldn’t worry too much about this defect as it doesn’t alter the taste unless it’s in a high concentration. 

6. Quakers 


This refers to unripened coffee beans. They cause a dry and papery taste in your drink and are often tough to spot. They usually have a light color and can be identified by tasting. 

The 4 Common Roasting Mistakes You Should Avoid 

1. Not Taking Notes

Proper resignation of curves and cupping notes is highly essential if you want to replicate the last batch or achieve high-grade consistency. Monitor all the temperatures at every stage from the beginning to the end. It is advised to note them down every 30 seconds for high accuracy. Some air roasters and ovens also have programs that allow for automatic timekeeping which comes in handy. 

2. Rushing To Drink The Beverage 

Coffee Roasting Defects

Once you take your beans out of your roasting setup, the urge to taste them starts to take over. However, you should give your coffee beans ample time to release the carbon dioxide that they were exposed to while heating. 

For this purpose, you must let them sit for some time. The duration could be anywhere between twelve hours to seven days depending on factors like variety, profile, and altitude. The sweet spot lies around 3 days. 

The general rule of thumb suggests that the lighter you want your coffee to be, the longer you should let it sit. 

3. Not Preheating The Equipment

This especially applies to people who live in colder regions. Depending on your location, the temperature of your equipment can naturally fluctuate. If you avoid the preheating step, then the heat will be distributed unevenly which can cause scorching defects. 

Bringing the temperature of your equipment to a certain level will also help you stay more consistent and have accurate readings irrespective of the weather. 

4. Inadequate Roasting

This is the most common reason behind the occurrence of roasting defects. To prohibit this from happening, I recommend you to have an idea of what your coffee beans should look like at the end. 

The right amount of roast comes down to your personal taste. However, there are some visual indicators that might help you avoid inadequate roasting. 

Underdeveloped coffee is usually light in color and cannot be crushed with your thumb when pressing it against a table or hard surface. You should wait until a slight golden texture starts to develop. This means that your coffee bean is nearing the first crack stage. 

As for the flavor, underdeveloped coffee gives out a grainy taste which gives your coffee a slightly brothy texture when prepared. When it comes to over-roasting, anything beyond five minutes of the second roast is said to be too dark. The dark brown color should be a good indicator that your coffee has reached its roasting limit. 

Heating beyond this may end up causing you to have chipped beans. 

Know Your Green Coffee

green coffee

It is also worth noting that not every green bean will have the same roasting time. Learning the fundamental idiosyncrasies of each coffee bean you work with will take a considerable amount of time and practice. 

Coffees that come with a wider spread take longer to heat up, whereas low-density beans begin to heat up at the beginning of the process itself. On the other side of the spectrum, high-density coffees begin to take the heat in the latter stages instead. 

Coffees that have a high moisture content also require more time. 

Monitoring The Rate Of Rise 

This is the rate at which temperature begins to increase during the roasting process. Roasters should avoid a low ROR, as it indicates that the beans are taking a long time to crack. This can lead to stalling of the beans which gives rise to the baking defect. Monitoring the temperature of your coffee and gathering its compositional data may help you better analyze the energy build-up in the beans. 

Pre-ground coffee makers usually hide these defects, as their produce is already mixed. On the other hand, if you are a home roaster, you have the option of identifying these roast defects and adjusting your practices accordingly. Combating and eradicating these defects is a labor-intensive task, but the taste that you get in the end is worth the hard work. 

Getting the perfect roast might take some time. That being said, always ensure that you exercise all the precautions mentioned above and try a variety of different beans to explore a multitude of taste profiles.