In short...
- Typical roasting temperatures used for specialty coffees do not affect caffeine content.
- The physical changes of the coffee bean (volume and weight) define the concentration of caffeine in the bean.
- Caffeine content also depends on the variety, the species and the brewing technique.
...if you have time, dive deep into the full article
Dark, light or maybe medium roast? Or is it all the same?
In this week’s post, we will face one of those coffee myths or secrets where opinions often differ.
Two perspectives: caffeine content by roast level
Does the roasting degree have any influence on the caffeine content in roasted coffee beans? Or in other words: “Does darker coffee have more caffeine than lighter roasts or vice versa?”
From my personal experience and according to popular belief there are two schools of thinking about this:
1. Lighter roasts have more caffeine
Some people think that lighter roasted coffee beans have more caffeine because they are roasted at lower temperatures, and for that reason, the caffeine will not degrade.
2. Does dark roasts have more caffeine
Other people think that darker roasts have more caffeine because those coffees "feel" stronger or are more bitter.
How roasting temperature does (not) affect caffeine content?
The primary assumption here is that the caffeine content is somehow altered or changed by the typical high temperatures during the roasting process.
But the reality is that to modify the caffeine content within the beans, the roaster would have to raise the temperature so high that the beans would transform into great charcoal for BBQ. Several sources report that the melting point of caffeine is somewhere between 235 and 238 degrees Celsius.
In most cases, coffee roasters will not pull the roast up to that point, especially when specialty or higher quality coffees are being roasted. As a conclusion, the caffeine content at normal roasting temperatures remains basically unchanged.
So light and dark roasts have the same amount of caffeine? Wait! We have not finished yet.
How does the physical change of roasted coffee beans affect caffeine content?
Caffeine content by mass
A coffee bean can be seen as a certain amount of dry mass with a particular weight. The caffeine is a part of this dry mass and has a certain weight, too. Usually, caffeine makes one percent of a coffee bean’s dry mass.
In other words: just imagine for a moment that a coffee bean would weigh 100mg, then the caffeine content is 1mg.
But when coffee is roasted it starts to lose weight (usually 15-20 percent), mainly due to the loss of water. For our imaginary coffee bean, it means that after being roasted it has less than 100mg of weight.
Let’s say it lost 16 percent in a medium roast which would mean that in the end, the bean remains with a weight of 86mg.
As we know, caffeine remains unchanged, the proportion between caffeine weight and bean mass has changed. We could say that caffeine is more concentrated now.
The more the bean is pushed through the roasting process, the more weight it loses and the higher the concentration of caffeine in the bean.
Caffeine content by volume
Another effect of roasting is the change of the volume of the coffee bean. Basically, when the volume increases, more the coffee is pushed through the roast. Conversely, to the caffeine by mass theory, the concentration of the caffeine decreases when it is considered by volume.
Let’s imagine that the coffee bean would have a capacity of 10 ml and the caffeine would have a volume of 1 ml. As the bean volume increases and the caffeine content remain unchanged the concentration of the caffeine is lower. The darker the roast, the more volume the bean has and the lower the concentration of caffeine is.
Other determinant aspects for caffeine content
It depends on how you look at the topic. Both teams (dark and light roast team) are right. Like always in coffee, it really, really depends on the perspective you choose.
But remember that the roasting degree and the related caffeine content is only one of many determinants for the caffeine content in the final beverage. The choice of the species (robusta or arabica coffee) and if they are blended or not will also have an impact on the caffeine content as robusta has in average double the amount of caffeine than arabica.
Moreover, within the arabica species, you can find different varietals which have different amounts of caffeine. Just imagine if you could choose the right varietal based on the amount of caffeine.
Finally, there is the whole brewing process, from weighing the beans to brewing and extracting the coffee which determines how much caffeine comes into our cup and finally into our body.
Let’s wrap this up
I hope I could explain this secret or speculative topic of caffeine content and roast degree. The learning in a nutshell:
- The caffeine content in coffee is barely changed by the roasting temperature unless the roaster pushes the beans to charcoal degree
- The caffeine content has to be seen in relation to the volume or the weight of the coffee bean and the proportion to one of both determines whether the coffee bean has more or less caffeine. The physical change of the bean is the focus here
- The caffeine content in your brew will depend on so much more factors than the roast degree, including the brewing technique, the coffee species and varietal and if there is a blend or not
I hope you liked this post. Give me a comment or share this post with your coffee drinking friends if you think it could help them.
We keep in touch and stay caffeinated ;)
References
Caffeine in Coffee (2015, April 23). Coffee Chemistry. Available at: https://www.coffeechemistry.com/chemistry/alkaloids/caffeine-in-coffee#disqus_thread (Accessed on 2017, July 9)
Debunked: Do Light or Dark Roasts Have More Caffeine (2016, November 17). Perfect Daily Grind. Available at: https://www.perfectdailygrind.com/2016/11/debunked-light-dark-roasts-more-caffeine/ (Accessed on 2017, July 9)
Caffeine. National Center for Biotechnology Information. PubChem Compound Database; CID=2519, Available at: https://pubchem.ncbi.nlm.nih.gov/compound/2519 (Accessed on 2017, July 9)
Media Credits
Title picture by PICSELI on Unsplash
Corrected & Revised by Andrea Letzner
