Last Updated on June 27, 2023 by Barry Gray
The problem with roasting coffee beans is that they start to deteriorate and lose some flavor and aroma over time. That means your coffee experience worsens the longer you wait between roasting and brewing your coffee.
So, this opens up an interesting question for me.
If roasting coffee beans initially brings out all the flavor and unforgettable taste experience, will roasting the coffee beans again do the same thing?
I do not advise trying to reroast coffee beans. Most times, you will not roast the bean but rather cook it, and that will do nothing to enhance the flavor profile. Actually, it will do the opposite resulting in a coffee that tastes bland and unappealing and may result in you simply purchasing new beans.
But I also know some people out there are advocates for trying to reroast coffee beans. So, I thought it would be worth exploring in greater detail.
Do Reroasted Coffee Beans Exist?
I doubt you will find reroasted coffee beans, sometimes referred to as double-roasted, on a shelf in a store. I’ve searched and just could not find anything, and I feel that’s for a good reason.
But here’s an important point.
You can actually do it. All it takes is for you to repeat the roasting process, and the bean is technically then double-roasted.
Yet, that doesn’t automatically make it a good thing.
What Actually Happens When Roasting Coffee Beans?
Before diving into why I would not double-roast coffee beans, let me take a minute to walk you through what happens when you roast coffee beans in the first place.
Roasting coffee beans is a necessity. This process releases the aroma, taste, and oils from the beans, and it means you can grind them down and enjoy your coffee.
But hold on because I need to dive into some chemistry to tell you what’s happening here.
A Chemical Reaction
I found the chemical reaction interesting when I initially looked into roasting coffee beans several years ago. In effect, the roasting process replicates the bean ripening in nature, and that’s cool.
What people don’t think about is the fact you have literally hundreds of different chemicals within a coffee bean. Those chemicals are forced through a change when you heat and roast them.
But that’s what we want to happen.
We want those chemicals to change as that releases the flavor and forces the oil in the bean to come out, leading to a smoother drinking experience.
As I look at what’s contained within a coffee bean, I focus on two key areas: sugars and acids.
Those two components are very important, and it’s because of the major role they play in determining the overall taste of your coffee.
Take the sugar aspect of your coffee beans.
When you roast the bean, the sugar starts to caramelize. The longer you roast it, the more caramelized it becomes.
Still, it also changes from being sweet into something that has more of a bitter taste to it.
That is why dark roast coffee tends to be more bitter when you really focus on the flavor.
What is the Maillard Reaction?
This process of the amino acids and sugars changing chemical structure when roasted and becoming caramelized is also known as the Maillard Reaction. It’s not only something that happens with coffee beans, so it’s not unique here.
But here’s the part I found to be the most important.
When you reroast coffee beans, you do not recreate the Maillard Reaction. That just does not happen.
You get one shot at creating this reaction, and the outcome of a second attempt will fall way short of your expectations.
What Happens to Coffee Beans When You Reroast Them?
If you intend to attempt to reroast your coffee beans, then I fully expect one outcome to happen: burnt beans.
I tried it out by getting some dark roasted coffee beans and put them in my oven to reroast them. Sure, the theory seemed good, but the outcome was horrible.
I felt the beans, after grinding them down, had an unpleasant taste. Even the aroma was not what I expected, and I could instantly tell the entire thing would be a significant disappointment.
Why Do They Burn?
It’s interesting that the beans burn, but it makes sense when you look at things more closely.
The problem is actually connected to the oil that comes out of the bean during the initial roasting process. The oil sits on the bean’s surface and coats it, and that’s where you have the problem.
When you reroast your coffee beans, you actually burn the oil onto the bean itself. That burnt taste clearly stays when you then grind the beans, and it’s a taste you cannot ignore.
What Will Reroasted Coffee Beans Taste Like?
Let’s get one thing straight here, coffee is all about the taste, and we all have our own preferences. However, I can guarantee that when you reroast coffee beans, they will taste bitter.
Look, I know some people love very bitter coffee. Yet, I’d argue most people have their limits when it comes to bitterness where it becomes too much.
That’s the issue with reroasted coffee beans. You will only enjoy them if you love extra-bitter coffee.
It’s all because of that issue with the sugar caramelization I mentioned earlier.
But even though I don’t personally appreciate that degree of bitterness, it’s not the main issue I have with the taste.
The problem I have is the burnt flavor I’ve mentioned previously.
Think about the difference in flavor when you make toast. Think of the difference when you burn the toast to such an extent it’s almost as if it’s charcoal.
Very few people like toast that has been done to that extent, and a coffee bean is not too different.
When I tried reroasting coffee beans, all I got from a taste perspective was a sense of the beans being somewhat stale, lacking in a better balance of flavors, and that bitter taste coming through.
Actually, I struggled to drink the coffee. It was simply too much for me to contend with.
How Will the Acidity Change in Reroasted Coffee Beans?
Acidity in a coffee bean is an integral part and is directly linked to the potential enjoyment of the coffee.
The roasting process creates this balance of the different citric acids and flavors in the bean, and it does change depending on whether you have a light roast, medium, or dark roast coffee.
If you reroast coffee beans, you will effectively create an imbalance in those acidity levels. This imbalance will alter the bean’s flavor profile, and the coffee you once liked may become undrinkable for some people.
But that’s not all.
As this acidity balance changes, so will the balance of another set of chlorogenic acids.
The problem with chlorogenic acids is that they are not floral and fruity but are bitter to the taste.
It’s almost as if one set of acids, which are the more pleasant ones, drops as the more unpleasant ones increase in potency.
Will Reroasted Coffee Beans Have the Same Aroma?
Alongside the flavor, I feel the aroma of coffee beans will always be something that draws people to coffee. You will know exactly what I mean if you have been around many different coffee beans in the same space.
The initial roasting process plays a crucial role in developing the aroma, so what happens if you reroast the beans?
The answer is you will not get some sort of re-release of the aroma. It just doesn’t happen.
Instead, I felt disappointed.
What happens with the aroma is it forms a part of the Maillard Reaction. As that only occurs once, then the release of the aroma follows likewise.
So, what was my experience of the aroma?
I think the only way to describe it was the coffee beans had an aroma of something burning, and that’s not a pleasant smell.
Will Reroasting Under-Roasted Coffee Beans Help the Flavor?
The final point I want to address is one where I feel people make the mistake of believing something that is not true: reroasting under-roasted beans to make them taste better.
If you have a light or medium roast and want more caramel or oil, should you reroast the beans to turn them into a dark roast?
Absolutely not, because it won’t work.
Sure, the bean will become darker, but you will still experience the horrible bitterness of the bean rather than a smoother bitter taste if you had only roasted the beans correctly the first time.
If you want a darker roast, the only thing you can do is to get dark roast coffee beans to begin with. You cannot reroast them and hope to achieve the same result.
But What About Stale Beans?
Coffee beans go stale over time. You cannot completely stop this from happening, and double-roasting your coffee beans will not help.
The problem with stale beans is the oil from the bean has already become rancid. Trying to reroast the beans will only enhance that rancid taste, so you are wasting your time trying this.
My Recap on Reroasting Coffee Beans
I feel this concept of reroasting coffee beans is something a number of people contemplate, so here are my key points for you to take away with you.
- Reroasting coffee beans will destroy the flavor
- Your beans will become overly bitter
- You will burn the beans due to the oil
- You won’t roast the beans; you will bake them
- You cannot reproduce the aroma by reroasting
- The Maillard Reaction only happens once
- The sugars in the bean will only caramelize once
- The flavorful acids will decrease, and the horrible acids will increase
- You cannot reroast under-roasted beans and get good results
I think I should have managed to convince you that reroasting coffee beans is a bad idea.
So, while it is possible to reroast coffee beans, I wouldn’t advise it. Instead, what you will get is coffee that doesn’t taste good and is overly bitter.
Instead, try to get freshly roasted beans, grind them down, and use them as soon as possible.
Alternatively, look at potentially freezing the beans to help them last longer, and in doing so, you will manage to continue to enhance the flavor.