Does Old Coffee Lose Caffeine

In this brief article, we will answer the question, “does old coffee lose caffeine?”, how long does coffee (stored and brewed) retain its caffeine content, plus some other interesting facts about the chemicals present in old coffee.

Does Old Coffee Lose Caffeine?

No, old coffee does not lose caffeine. 

Even though some of the features of coffee begin to degrade soon after being exposed to air, such as its taste, color, and aroma, caffeine is much more stable and can last for months without any significant changes in potency.

Even a freshly brewed cup of coffee that’s been left on the counter for hours will retain its caffeine content; it just doesn’t evaporate like the flavonoids present in coffee.

This also explains why old or spent coffee tastes bitter; the flavorful ingredients have deteriorated, leaving behind only bitter-tasting caffeine. 

So, unless you particularly remove caffeine from coffee beans and make a decaf version, coffee will retain its caffeine content.

Caffeine is a naturally occurring compound present in various foods and drinks that increase alertness and provide a boost of energy. This water-soluble alkaloid is a stimulant that acts directly on the nervous system.

Do Old Coffee Grounds Lose Caffeine?

Again, no; old coffee grounds do not lose caffeine. As mentioned, caffeine is comparatively much more stable than most of the other chemicals found in coffee. 

Probably the only striking difference between coffee made from fresh grounds and that made from coffee grounds that are several weeks or months old is the flavor.  

Simply put, the older the grounds, the milder and less complex the flavors, but the intensity of caffeine remains more or less the same.

However, roasting can slightly affect the caffeine content of the beans. Caffeine is an alkaloid that is thermally stable. Some of it is lost during the roasting process, but a small part may be lost during the sublimation process. In addition, changes in the microstructure of coffee beans occur during roasting. The pores close, which contributes to the accumulation of inorganic gasses inside the beans. The pressure inside increases, which causes them to crack (characteristic crackling sounds), and, along with the roasting gas, a small amount of caffeine may also be released. Caffeine losses may be greater at higher roasting temperatures (1).

How Long Does Caffeine In Coffee Last?

If coffee is stored under optimal conditions, its caffeine content can potentially outlast all of the other chemicals and the coffee grounds’ attributes, including flavors and oils – almost four years in most cases of roast coffee.

Optimal storage conditions include:

  • Cool, dark environment
  • Lack of moisture
  • No exposure to direct heat or sunlight
  • No sudden variations in temperature
  • No insects or rodent infestation 

Besides optimal conditions, the packaging material should be moisture and oxygen resistant. A study compared different packaging materials for the storage of roasted ground coffee for 12 months at 28°C and 80% (RU). There was a loss of phenolic compounds in coffee stored in aluminum-laminated polyethylene and polyethylene terephthalate packages. No significant changes were observed for the caffeine content (2). 

Caffeine content and flavor also depend on the brewing process used. For instance, filter coffee does not taste as strong as espresso because the latter contains less water and is more concentrated. However, its caffeine content is higher, since the water draws more caffeine from the coffee beans. The caffeine amount in the coffee depends on the following factors: the influence of species, brewing time, water temperature, pressure, degree of roast, grinding degree, water type, water/coffee ratio as well as other factors (such as geographical origin) (1).

Caffeine Content Of Different Types Of Coffee Beans

The most produced and consumed coffees, known as Arabica and Robusta, differ significantly in their caffeine content. Robusta (including all varieties of Coffea canephora) contains more caffeine than Arabica (1). Here are the caffeine contents of different varieties of coffee beans:

  • Arabica beans contain only 1.5 percent caffeine content. They are sweeter than other varieties and don’t taste earthy and harsh. These beans are commonly grown for various flavors and aromas and produce finer and more delicate coffee.
  • Robusta beans contain 2.7 percent pure caffeine and have a more earthy and burnt flavor. They can be used on their own and also in a blend of different proportions. 

Caffeine is formed in unripe coffee beans and its amount increases as they mature. The higher content of caffeine in Robusta coffee is due to the greater expression of certain genes, such as CaXMT1, CaMXMT1, and CaDXMT2, which are associated with caffeine accumulation in coffee beans (1). 

Some other factors that influence how long caffeine will last in a bag of coffee include the time elapsed since the coffee beans were processed, how intensely they were infused, how long has the bag been opened (if it is in use), and when was the coffee ground.

Moreover, even used coffee grounds, or those that are past their expiry date tend to have a substantial amount of caffeine in them. Again, this is because of the compounds’ stability and also because caffeine is among the last ingredients to get extracted in standard coffee brewing. 

What Happens To Caffeine If You Reheat A Cup Of Old Coffee?

Nothing really; the caffeine content remains as it is. Reheating a cup of coffee only evaporates a significant amount of what remains of the coffee’s aroma. However, it will make the taste worse.  Massive odor and flavor losses are the consequence of the water solubility of essential oils of coffee and the formation of volatile flavoring substances with oxygen, stated that the change in aroma might due to oxidation, where aroma compounds oxidized to produce a new volatile compound so the coffee aroma fades (2). 

This means that reheating a previously hot cup of freshly brewed coffee will not have the flavor and aroma that you’re looking for, but it will still be able to give you that kick that comes from caffeine stimulation.

Conclusion

In this brief article, we will answer the question, “does old coffee lose caffeine?”, how long does coffee (stored and brewed) retain its caffeine content, plus some other interesting facts about the chemicals present in old coffee. 

If you have any more questions or comments please let us know.

References

  1. Olechno, Ewa, et al. Influence of Various Factors on Caffeine Content in Coffee Brews. Foods, 2021, 10, 1208.
  2. Agustini, Sri, and Mimi Kurnia Yusya. The effect of packaging materials on the physicochemical stability of ground roasted coffee. Curr Res Biosci Biotechnol, 2020, 1, 66-70.