Other than the flavor and aroma of the coffee, we drink coffee for its caffeine content. Caffeine provides an invigorating effect and improves alertness hence the reason coffee is the go-to morning drink or when we feel drowsy.
Drinking a deliciously brewed cup of coffee enhances your energy levels within about 30-45 minutes. Coffee lovers are aware that coffee flavors and aroma degrade with time. However, misconceptions surround the question as to whether coffee loses its caffeine over time.
Does coffee lose caffeine over time?
No, the coffee retains its caffeine content over time as caffeine is a fairly stable compound. Whether the coffee is refrigerated, in the pantry, or sitting on a table, its caffeine content does not change over time. Old coffee still has nearly its original amounts of caffeine despite losing its freshness.
Unlike the volatile compounds of coffee flavors and aromas that dissipate with time, caffeine remains intact. Whether you are dealing with old coffee beans, old brewed coffee, or ground coffee, the age of the coffee does not affect its caffeine content.
What Is Caffeine
Caffeine is a natural stimulant that occurs in the fruits, leaves, and seeds of various plants. Kids Health states that caffeine increases alertness by stimulating the central nervous system and also uplifts your mood. Pure caffeine is a white substance that has a very bitter flavor.
Despite caffeine’s health benefits, caffeine overuse is linked to side effects such as jitters, lack of sleep, dizziness, and anxiety. The FDA warns that highly concentrated or pure caffeine such as in some dietary pills or supplements is highly potent and can cause toxicity and even death.
Caffeine is fairly soluble in water and its solubility increases rapidly with the increase in water temperature. Caffeine remains stable when exposed to heat until about 460.4℉ when it starts to break down.
Caffeine in Coffee
Caffeine occurs naturally in coffee beans but can be removed through decaffeination. Once the coffee beans are processed as either decaffeinated beans or regular beans, the caffeine level largely remains intact for the life of the coffee beans.
Although very dark roasts have slightly lesser caffeine content than lighter roasts the difference is insignificant when you account for the increase in volume and loss of density in the darker roasts.
The way you store the coffee beans does not affect the caffeine content. Effectively, any circumstances that interfere with the caffeine content during storage such as accidentally soaking the coffee beans in water over time not only dissolve some of the caffeine but also render the beans unsuitable for brewing.
Similarly, brewed coffee retains its caffeine level even as it loses its flavor and aroma over time. An 8oz cup of coffee has about 95mg of caffeine and the level of caffeine remains the same no matter how long you keep the coffee.
You may want to read our post about the caffeine in a tablespoon of ground coffee to further understand this topic.
How Caffeine Affects the Taste of Coffee
Caffeine accounts for only a fraction of the bitter flavors in your coffee. The flavor of caffeine is easily influenced by the more potent coffee flavors and characteristics such as the brightness of lighter roasts.
Most people wrongly associate caffeine with the bitter taste of coffee and imagine that because old coffee becomes dull, then it has lost its caffeine. The fact is caffeine is still present in old coffee and does not evaporate even as the volatile flavor compounds evaporate.
The bitter taste of dark roasts has less to do with caffeine content and more to do with the evaporation of the brighter flavor compounds during roasting.
However, very large amounts of caffeine can influence the taste of coffee. For example, Robusta coffee has double the caffeine content of Arabica coffee hence it’s bitter than Arabica.
How Long Does Caffeine Last in Coffee?
Caffeine lasts the full life of coffee until you drink or discard the coffee. When you drink coffee, your body absorbs the caffeine within 30-45 minutes and the caffeine can last in your body for up to 3-4 hours before the body excretes it.
Old unbrewed coffee grounds have the same amount of caffeine as when they were fresh.
How To Reduce the Caffeine in Coffee
1. Use Decaf Coffee
Decaf coffee has nearly all of its caffeine removed and has similar hydrating benefits as drinking water as well as the health benefits of regular coffee. Decaf coffee is an excellent option to enjoy your favorite cuppa without worrying about the caffeine effects.
2. Lower Brewing Temperature
Caffeine dissolves more readily at a higher temperature than at lower temperatures. However, cold brew coffee is brewed using more coffee grounds than regular coffee.
Read about the caffeine in cold brew coffee.
3. Arabica Coffee Beans
Arabica coffee beans have about half the caffeine content in robusta coffee. Arabica coffee also has a far superior taste as compared to the harsh and bitter taste of robusta.
4. Use Lesser Amounts of Grounds
Adjusting your grinds to water ratio directly impacts the amounts of caffeine in your coffee. Reducing the quantity of ground coffee lowers the level of caffeine.
5. Adjust The Brewing Duration
Longer brewing times increase the time of contact between water and coffee grinds hence more caffeine dissolves.
6. Brewing Method
Different coffee brewing methods use different brewing temperatures, times, and coffee ratios. All these factors can, although to an insignificant extent, determine the amount of caffeine that ends up in your cup.
For example, a Chemex brews coffee in almost double the amount of time that Hario V60 takes. Espresso-based coffee has lesser caffeine than equal amounts of both filter and auto-drip coffee.
Cold-brew coffee uses cold water that extracts less caffeine, acidity, and bitterness but the longer steeping time and higher coffee ratio mitigate against the effect of cold water.
7. Use Very Dark Roasts
Although the loss of caffeine during roasting is quite insignificant, brewing with darker roasts while also implementing other tips such as lower amounts of grinds as well as adjusting the brewing temperature, and time can yield significantly lower amounts of caffeine.
Caffeine remains intact despite how long the coffee lasts. Although caffeine has a bitter flavor, it accounts for very little of the coffee flavors. Hence the reason that stale coffee can be flat despite having its caffeine content intact.
Other than caffeine, cafestol is another component in coffee that you may want to read about.
FAQs About Whether Coffee Loses Caffeine Over Time
Does Reheating Coffee Destroy Caffeine?
Reheating coffee does not break down the caffeine at all. Caffeine only starts to melt at a temperature of about 238℃/460.4℉ that is unachievable when brewing or reheating coffee. Therefore, reheating your coffee will only break down the volatile flavor and aroma compounds but has no effect on the caffeine.
See this post that discusses whether you can warm cold brew coffee.
Does Reusing Coffee Grounds Reduce Caffeine?
Although used coffee grounds have less caffeine than fresh grounds they still have a significant amount of caffeine. According to Coffee Informer, used coffee grounds have about 3.59-8.09mg of caffeine per gram of coffee.
Fresh coffee grounds have about 12mg and 22 mg of caffeine per gram of fresh coffee grounds for Arabica and Robusta respectively. The amount of caffeine in the used coffee grounds depends on the brewing method. A brewing method that extracts lesser caffeine such as cold brew yields used grounds that have more caffeine and vice versa.
We do not recommend brewing coffee with used grounds because the coffee is weak and has less flavor if any. However, there is evidence of reusing spent coffee grounds in coffee cultures such as the Ethiopian as well as the Eritrean coffee rituals that brew up to 3 times using the same grounds.