Have you ever made yourself a cup of coffee and then left it on your kitchen counter and forgot about it? If so, then you already know that coffee can taste quite different after several hours. But does the level of caffeine start to diminish over time?
When it comes to coffee, there are some things that are a given, and one of those things is the amount of time that caffeine lasts in coffee, whether or not it is brewed.
So the question is: Does Coffee start to lose its Caffeine over time?
The answer is no. Coffee continues to maintain its caffeine levels over time (How Much Caffeine is in Instant Coffee? Is it worse than Drip Coffee?). The only time it differs is when you remove the caffeine out of the coffee beans in order to make decaf coffee – Does Decaf Coffee Have Caffeine? Is Decaffeinated Without Caffeine?.
If you were to brew a cup of coffee (Best Coffee Cup Material: Ceramic vs Glass vs Steel vs Plastic) right now and then left it on your kitchen counter for 8 hours before drinking, the same amount of caffeine would still be in the coffee. The caffeine would still do its job of providing you with a boost of energy and help your brain remain focused and awake – Can Coffee Make You Tired?
However, the flavor will be practically gone, since when it comes to the shelf life of coffee, the flavanols tend to be one of the first things to go. To help you understand the entire process and what takes place in your cup of coffee after you have brewed (Can You Freeze Brewed Coffee?) it, we will first discuss caffeine in general.
General information on Caffeine
Caffeine works as a kind of “fake” plug for the tiredness receptors inside your brain. That is a basic version of the way that coffee works – Brewing basics when making pour-over coffee.
Caffeine is a solid substance. If it were taken out of the coffee beans (Can You Eat Coffee Beans? – Should you Eat them?) and laid out, it would show a dry, white powder.
For example, it is similar to how sugar is a solid substance. Caffeine doesn’t evaporate but it is water-soluble. Over time, the water mixed with caffeine evaporates, and you are left with an identical amount of caffeine inside your cup of coffee that you first started with.
The melting point of caffeine is 235 C/455 F. That is much higher than any method of brewing coffee (How to Brew Low Acid Coffee for Upset Stomachs) requires or can produce. This means the caffeine will not break its bonds or melt in a cup of coffee, including high-pressure and hot espresso.
No method of brewing coffee will eliminate the caffeine, and it doesn’t evaporate when it is exposed to air.
Pure caffeine is available in the form of a dietary supplement. However, it is very easy to overdose on, since your body only needs a couple of milligrams.
So if there are 80-175 mg/0.002 to 0.006 ounces of caffeine in your regular cup of coffee, that is the exact amount of caffeine that will remain if all of the water were to evaporate from your cup of coffee at the same time.
After you brew a Cup of Coffee, what happens to it?
A cup of coffee has a fairly brief lifespan. That is partly due to the fact that you have a tendency to drink your coffee right after brewing it, and it is partly due to the flavor fading after around one hour.
So a cup of coffee that is freshly brewed will be flavorful and tasty for around one hour (assuming it is kept at a constant temperature, like storing it in a thermos) before it starts to lose some of its punch.
That is actually only true if your coffee stays hot or warm at the very least. As the liquid starts to cool down, it will slowly start to evaporate. The aroma will also start to fade.
That may cause you to think the caffeine has disappeared as well since that is tied very closely to the way you perceive how your coffee tastes. Simply put, bland-tasting coffee (What is Coffee Bloom? – Does it Affect Taste and Aroma?) seems weak to your brain (when it comes to caffeine), so you will assume there is not a lot of caffeine inside your cup of coffee.
What happens if you reheat a Cup of Coffee?
That both helps the taste and also makes it worse at the same time. However, there is still the same caffeine content. Reheating coffee that is already infused with caffeine will not give you the effect you are searching for, other than to warm your coffee up again.
That is why fresh coffee tastes so good, and why stale coffee (even when kept warm) isn’t very satisfying.
Reheating coffee that you have brewed already just works to evaporate quite a bit of the remaining aroma of the coffee. That means that even when there is the same amount of caffeine as 3 hours ago, it will appear to be lower since most of the taste of the coffee is gone. It will still taste like coffee, but the flavor will not be the same.
The way your coffee tastes can affect the amount of caffeine that you detect
You may be wondering why we are discussing taste when you wanted to know about the caffeine content in coffee. They are very closely related, and one of them influences the other.
In a cup of brewed coffee, the caffeine is what provides most of the ‘coffee’ flavor and bitterness to the infusion. Also, there is the aroma or flavor apart from the caffeine that is present as well – How Much Coffee is in a K Cup?
That is how you notice the hint of vanilla, chocolate, or fruity notes. Each specific coffee has its own aroma and flavors.
The earthy tones and bitterness are specific to the actual caffeine. This is why, for most people, it is easier to enjoy Arabica beans because they have just a 1.5% caffeine content.
Compared to Robusta beans they are sweeter, and that means they will not taste as harsh and earthy, and that in turn affects how caffeinated or strong your coffee will seem to you. Arabica beans are mostly grown for different aromas and flavors and make a more delicate and finer cup of coffee – Do cream and sugar reduce caffeine in coffee or do they only add calories?
Robusta beans, on the other hand, are 2.7% pure caffeine. They have a distinct earthy flavor, and at times taste a bit burnt. It is a potent coffee, and not everyone is comfortable with this type of flavor.
Sometimes they are used by themselves, or in varying proportions, or as part of a blend. That will affect how your cup of coffee tastes, so a cup of coffee brewed with Robusta beans, or mainly Robusta, will have a stronger taste, and will tend to have a caffeine content that is higher as well since Robusta beans have higher amounts of caffeine.
Caffeine content and taste will also vary depending on the brewing method that you use, and whether or not you drink your coffee black. For example, expresso has a stronger taste than filter coffee, since espresso uses less water and is more concentrated.
However, filter coffee has higher caffeine content since there is more time for the water to draw out the caffeine from the coffee grounds.
How you store your coffee will affect the flavor but not the caffeine
We have discussed how caffeine and taste are related, and why drinking a stale cup of coffee could cause you to think that the caffeine has disappeared (or is mainly gone) Does Coffee Cause Acne? – Is Coffee the Reason for Skin Breakouts?.
But hat about coffee that has never been ground or brewed? How about coffee beans that have been roasted and stored inside of a bag?
The aroma will fade over time, and you will start losing the notes specific to that certain blend of coffee beans (Arabica vs Robusta Coffee Beans – What Is the Difference?). If the coffee beans were infused with a specific aroma, this will be the first thing to go.
It will, of course, depend on how long ago the beans in the bag were process, how strongly the beans were infused (if at all), and how long the bag has been open, how long ago the coffee beans were found, etc.
Generally speaking, coffee beans are the freshest for 2 to 3 weeks after they are roasted. However, bags and airtight containers can make the time frame longer. Anytime you are shopping for coffee, look for the date that it was roasted instead of its best by date.
Roasted coffee beans will still have caffeine present for at least 4 years. That is how long unprocessed caffeine is stable in coffee beans. It begins to break down some, but very slowly after the first four years. The same thing is true when it comes to ground coffee.
Most coffee bags don’t last at a coffee shop or house for 4 years so you should be safe.
Hopefully, this article helped you determine whether or not your coffee is still okay. Many people think about it but rarely ask any questions. Here is the answer for you and hopefully it helps.