Can You Reroast Coffee Beans?  (A Complete Guide)

Last Updated on May 6, 2022 by John Moretti

If you’re an avid coffee-lover, you are probably always looking for new ways to improve your coffee’s flavor and aroma. There are so many different types of coffee beans available today, varying from light roast to medium roast or dark roast. Each roast has a unique taste, aroma, and appearance. But now you’re wondering – can you reroast coffee beans to suit your specific taste preferences? 

Reroasting coffee beans to obtain a stronger flavor is not recommended. Roasting coffee beans for a second time affects the Millard reaction that gives the coffee its unique flavor and distinct aroma. Reroasting coffee beans leads to changes in the acidity levels of the coffee, which leads to overly bitter-tasting coffee with a flat, bland aroma. 

Coffee is one of those things where quality will, without a doubt, directly affect the taste. Does reroasting coffee beans affect the quality and taste of your brew? Read on to find out!

What Are Double-Roasted Coffee Beans?

Double-roasted coffee beans aren’t something you’ll find in the store. Unlike dark, medium, or light roast coffee beans, double-roasted coffee beans simply refers to coffee beans that have been roasted twice. Any roast can be double roasted by repeating the roasting process. You can even mix two different coffee bean roasts to create a combination of double roasted coffee. 

The main reason someone would want to roast their coffee beans twice is to release the flavor of the beans for a stronger coffee with a more pronounced flavor. However, as you’ll see later in the article, double-roasted coffee beans do not necessarily give you better-tasting coffee.

How To Reroast Coffee Beans

There are a few different techniques for roasting coffee beans. The one you choose depends on the equipment you have available and how much time you have, but the basic process for each technique is pretty similar. 

1. Pan Roasting Coffee Beans

Photo of a hand with wooden spoon mixing roasted coffee in pan

To start, heat up the pan or skillet to medium heat. Add your coffee beans and spread them in an even layer in the pan. Make sure you keep stirring the coffee beans so that they can heat up evenly on all sides. After 3-5 minutes, you’ll hear the first cracking sound. 

It usually takes about 6-7 minutes to hear the second cracking sound. Once this happens, the coffee beans have been roasted to a dark roast. Remove the coffee beans from the heat and allow them to cool. Keep the coffee beans stored in an uncovered container for at least 12 hours so that the CO2 gasses can be released. 

2. Oven Roasting Coffee Beans

Oven roasting your coffee beans is a popular roasting method that ensures your coffee beans are evenly heated on all sides.

All you need to do is spread out the coffee beans in an even layer on a cookie tray. Once your oven is heated to approximately 500 degrees Fahrenheit, place your pan in the middle rack. Wait about 2-3 minutes to hear a cracking sound. For a darker roast, wait up to 5 minutes to hear the second cracking sound.

Remove the coffee beans from the oven and allow them to cool. 

3. Air Fryer Roasting

For a healthy coffee-roasting technique, you can use your air-fryer. Preheat the air-fryer for about 3 minutes and place the coffee beans in the basket. Allow the air fryer to work for approximately 10 minutes, checking the beans a few times throughout. 

The first crack should be heard after a couple of minutes, followed by the second crack a few minutes after. 

After 10-12 minutes, remove the beans from the basket and place them on a cool surface.  

What Happens When You Roast Coffee Beans Twice? 

There are chemical processes involved in the roasting process of coffee beans. The heat used produces specific chemical reactions that play a significant role in producing the right coffee bean roast with the desired flavor and the right color. 

By double-roasting coffee beans, you are putting already-roasted coffee beans through a whole heating process again. The outcome may not always be what you expect since some chemical processes do not have the same effect on coffee beans when done for a second time.   

The Maillard Reaction Cannot Occur Twice 

Roasting coffee beans causes them to undergo a non-enzymatic reaction called the Maillard reaction. The Maillard reaction occurs when amino acids and sugars react to heat. This reaction occurs when coffee beans are roasted for the first time and is responsible for releasing the delicious aroma and the flavors of the coffee beans. 

One of the problems with roasting coffee beans a second time is that the Maillard reaction does not occur with the second roasting. This can lead to certain changes that may affect the quality of your coffee. 

Changes In The Flavor Of The Coffee Beans

Instead of improving the flavor of the coffee beans, the extra heat added with a second roasting only leads to the burning of the coffee beans. This can result in overly bitter-tasting coffee and may spoil the unique flavors and aroma of the coffee beans. 

If extra bitterness is what you were going for, then double-roasted coffee beans may be a good option for you! But keep in mind that the Maillard reaction cannot occur again, and you can end up burning the oils in the outer layer of the coffee bean. Therefore, instead of having a stronger taste, you will have bitterness accompanied by a somewhat stale, burnt flavor. 

Changes In The Aroma Of The Coffee Beans

Coffee beans roasted for a second time will not release the same wonderful aroma as coffee beans that undergo the roasting process for the first time. Roasting time has been found to correlate with the aroma and the taste of coffee directly. 

Coffee beans only release their unique flavor and sweet, floral notes with the first roasting process when the Millard reaction occurs. “Overcooked” coffee beans will not smell that great. The only aroma you will most likely experience when you reroast an already roasted coffee bean is a slightly rancid smell or something similar to that of burnt charcoal. 

The Acidity Of The Coffee Beans Lowers

The acidity levels of the coffee beans are the main factors that distinguish an exquisite cup of coffee from just your average cup of coffee. Once again, the balance of citric (acidic) flavors and aromas in the coffee is directly influenced by the roasting time and temperature. 

Heat and all the processes that go along with it will drastically lower the levels of organic acids in the coffee beans. They can also cause the bitter chlorogenic acids to concentrate. Therefore, coffee beans that are roasted for a second time will have an imbalance in acidity levels that will cause the flavor and aroma to be compromised. 

Can You Reroast Coffee Beans That Are Under-Roasted? 

If you want your coffee beans to have a stronger flavor, we recommend that you roast the beans for longer when roasting them for the first time instead of trying to roast them a second time. Roasting an under-roasted coffee bean again won’t give you better-tasting coffee. Rather, you will have a darker bean with a less than desirable bitter taste.  

Can You Reroast Stale Coffee Beans? 

Coffee beans go stale due to oxidation, which cannot be reversed. No amount of roasting will help revive the flavor in coffee beans once they have gone stale. Roasting stale coffee beans will, in fact, lead to burning of already rancid oils in the outer layers of the beans and cause them to have an even more bitter taste and burnt aroma.  


Photo of a pair of hand holding a cup of coffee

Reroasting coffee beans sounds like a quick and easy way to get better-tasting coffee when your roast just isn’t strong enough. But, instead of double-roasting and ruining all the components that give the coffee beans their sweet, nutty flavor, we recommend you try a stronger coffee bean roast or that you increase the time and temperature with the first roast. This way, you’ll have the perfect combination of nutty, bitter flavors and a great quality coffee!