Have you ever prepared a steaming cup of coffee only to forget it on your kitchen counter? A sip of brewed coffee that has been left lying around for a few hours can taste horrible.
Even freshly roasted coffee beans and grounds lose their flavor within weeks. But does coffee lose caffeine over time, along with its aroma and flavor?
Most of us drink coffee for its rich aroma, bold flavor, and caffeine content. Without these, what is coffee? This guide will tell you whether caffeine evaporates from coffee or not. Read on.
What Is Caffeine Actually?
Caffeine is a natural stimulant found in coffee beans, cacao beans, guarana berries, kola nuts, and tea leaves. It activates the brain and makes us feel more awake and less tired by blocking the adenosine receptors in the brain.
Adenosine is a hormone that lowers excitement and promotes sleep. When you intake caffeine, it binds to adenosine receptors to block the adenosine. So, you get a sharp boost in focus and energy levels.
Caffeine also increases adrenaline levels, making you feel more pumped and alert. Adrenaline is another hormone that increases heart rate and blood pressure, thus helping you react quickly.
Caffeine affects the brain chemically, which is why it’s commonly called a psychoactive drug.
In its natural form, caffeine appears as a dry white powder. It is soluble in water but doesn’t evaporate. Caffeine has a melting point of 235°C or 455°F. This is higher than what any coffee brewing method normally produces.
This means that the caffeine in a cup of brewed coffee will not dissipate or break, even if it’s an espresso brewed at high heat and pressure.
So, even though the water content in a cup of brewed coffee evaporates after some time, its caffeine levels stay the same! It will still give you the kick and energy boost you need to get through the day!
The only time you can expect caffeine to evaporate from coffee is if you specifically extract it to get a decaf version.
So, we can safely say that brewed coffee or even coffee beans or grounds don’t lose their caffeine content over time—even after days, weeks, or months!
Does Caffeine Evaporate from Coffee after a Few Years?
Caffeine doesn’t evaporate from coffee even after months, but what about years? Will it start to degrade after a couple of years?
Roasted coffee beans and grounds have a good amount of caffeine for about four years. Until that time, unprocessed caffeine in a bag of coffee beans or grounds will remain potent and stable.
After that period ends, the caffeine starts to break down at an extremely slow rate that’s almost imperceptible.
What About Used Coffee Grounds?
Since caffeine is the last thing to get extracted from coffee, you’ll often find a decent amount of caffeine remaining in used grounds even after brewing.
Before you think about reusing them to make another cup of coffee, know that caffeine is an extremely bitter compound that tastes horrible on its own.
Used coffee grounds do not have oils or other compounds to help balance the flavor of the coffee. All you’ll get in a cup of coffee made with used grounds is caffeine alone, which we’re sure you won’t enjoy.
If all you’re looking for is a caffeine boost without much care for the taste, you may go ahead and brew a cup of joe with used coffee grounds.
It’s not dangerous—unless you happen to leave the grounds in a warm room. In such a case, you can expect bacteria and mold to grow on the coffee grounds.
How Much Caffeine Is in Coffee?
An average cup of brewed coffee which is approximately 8 oz has about 95 mg of caffeine. However, note that caffeine content varies in different coffee beverages based on these factors:
- Coffee bean type – Different types of coffee beans, such as Arabica and Robusta, have varying amounts of caffeine. Robusta beans have a higher caffeine content than the more delicate and sweeter-tasting Arabica beans.
- Coffee type – Different coffee beverages such as espresso, instant coffee, and decaf coffee, have significant differences in caffeine content.
- Roast level – Light roasts have a greater caffeine content than medium and dark roasts.
- Serving size – The serving size of a cup of coffee can be as little as 1 oz or as big as 24 oz. Serving size has a huge impact on the caffeine amount per cup.
While an average cup of coffee has about 95 mg, the caffeine content can range from 70 mg to 140 mg. An espresso shot contains a high amount of caffeine, at about 63 mg in a serving size of 1 to 1.75 oz.
On the other hand, most instant coffee drinks have less caffeine content than regular brewed coffee. A cup of instant coffee contains 30-90 mg of caffeine.
Decaf coffee, despite being called decaffeinated, isn’t fully caffeine-free! It generally has about 3 mg of caffeine per cup on average but can range from 0 to 7 mg.
So Why Does Coffee Change Taste over Time?
If coffee doesn’t lose its caffeine content for years, why does it lose its flavor so quickly? This is because the flavonoids present in the coffee, brewed or not, evaporate faster as they are more volatile than caffeine.
Flavonoids promote healthy blood circulation and overall cardiovascular health. However, they also partly contribute to the bitter, astringent flavor of coffee, which is one of the main elements of its diverse flavor profile.
When flavonols evaporate from coffee, you are left with an ashy, cardboard-like taste. So, if you leave your bag of coffee grounds or beans unopened for weeks or months, they’ll lose their flavor and aroma as their flavonoid content depletes.
But this depends on how long it has been since the beans were harvested, roasted, and packed.
If you leave your coffee lying around for hours, you can also expect it to lose its punch once it cools down.
The only way to prolong the aroma and flavor of brewed coffee is by keeping it hot, or at least warm, for as long as possible. You can do this by storing it in a thermos or any insulated container.
Then why do you feel that your coffee has lost its caffeine when the flavor is gone? The brain tends to associate caffeine with the flavor of the coffee.
But the truth is, the caffeine is still there. You only have to deal with the stale taste of the coffee.
What Happens If You Reheat a Cup of Brewed Coffee?
As you know, coffee tastes best when hot. If you reheat your brewed coffee, thinking it’ll increase its flavor or caffeine levels, you’re wrong. Reheating a cup of brewed coffee will only evaporate what’s left of the aroma and flavor.
That’ll leave you with a coffee that tastes even worse—bitter and burnt. Since your coffee will no longer taste fresh, it will trick your brain into thinking that the caffeine content has also dropped, which is, of course, not true!
No matter how much you heat and reheat coffee, its caffeine won’t evaporate due to its high melting point.
How Can You Prolong the Shelf Life of Coffee?
To lengthen the shelf life of coffee, you should only grind your coffee beans just before you plan to use them. This is because a whole bean helps protect the flavor and oils of the coffee from oxidation, which causes stale coffee.
Note that ground coffee loses its aroma and flavor rather quickly, as oxygen can get inside them faster than beans. But if you buy only grounds, don’t fret!
There are ways to increase their shelf life, too. Store your coffee grounds in an airtight and opaque container, and don’t let the container sit open for too long.
Store your coffee in a cool and dark place to prolong its shelf life, but don’t freeze it! Freezing can reduce its flavor a bit.
Conclusion
So, does coffee lose its caffeine over time? Not unless you happen to have a bag of roasted coffee beans or grounds lying unused for more than four years.
Even after that, caffeine takes a long time to degrade and evaporate. So you can still enjoy a good amount of coffee for a long time.
Just be sure to enjoy it fresh so that you don’t end up with a stale, bitter-tasting coffee brew that tastes like cardboard!
We hope this article answers your query about coffee losing its caffeine content over time. You can also browse our website for more articles on your favorite drink—coffee!
Resources:
- Wiley.com
- NIH.gov
- BetterHealth.gov.au
- YourHormones.info
- HealthDirect.gov.au
- NCBI.gov
- HealthLineNutrition.com
- HealthLine.com
- NLM.gov
- JoyResolve.com
Last Updated on October 5, 2022 by Ashok Parmar
