Caffeine in Coffee
Which one of our coffees has the most caffeine? Lighter roasts have more caffeine than darker roasts, right? Cold brew has more caffeine than hot coffee, right? Or espresso? We get questions like this all the time, and the amount of misinformation on this topic out there is somewhat terrifying. Let’s dig into it!
There are really only two things that determine how much caffeine ends up in your brew:
1. The species of coffee you are brewing.
All of our coffees are 100% Coffea arabica, or arabica coffee. Arabica coffee has roughly half the caffeine content per unit mass as Coffea canephora, or robusta coffee. Therefore, if you did everything the same but brewed robusta rather than arabica, you’d get twice the caffeine in your cup. Robusta coffee is more bitter & woody, and less fruity than arabica coffee. Arabica coffee contains roughly 10 milligrams of caffeine per gram while robusta coffee contains roughly 22 milligrams of caffeine per gram. Remember, coffee is an agricultural product so there is always going to be a little bit of variation from bean to bean.
2. Your dry dose of coffee
The more coffee grounds you use, the more caffeine you will end up with in your brew. This is the major reason that cold brew almost always has more caffeine than any other brew method - people tend to use way more coffee grounds for cold brew than they do for any other brew method.
This isn’t quite as straightforward as it seems though. Most coffee professionals measure dose by mass, in grams, but many home brewers measure dose by volume, in scoops or tablespoons. This is where roast level enters the picture.
As a coffee gets roasted darker and darker, there is actually a negligible amount of destruction of caffeine; it doesn’t get burned off or changed into something else. What does happen is that each coffee bean expands more and more AND each bean weighs less and less. Both of these changes happen because the trapped moisture inside each bean is evaporating. The loss of moisture of course means that each bean has less mass, but also the pressure from the water vapor inside the cell walls of each bean actually makes the bean get bigger. The end result is that darker roast coffee is less dense than lighter roast coffee. And now we go back to measuring dose by mass versus by volume.
Scenario A: you always use two scoops of beans or grounds to brew your coffee. If you are using light roast coffee, you are actually putting MORE beans or grounds (we are talking about the number of beans or grounds, not mass or volume) into those two scoops than you would be if you were using dark roast coffee, because each light roast bean/ground is more dense than each dark roast bean/ground. You need more light roast beans/grounds to make up the same volume. What the caffeine content really depends on is the number of beans/grounds - there is a fixed amount of caffeine in each bean which doesn’t change as you drive off moisture. So if you are measuring your dose by volume, light roast coffee does indeed give you MORE caffeine in your cup than dark roast coffee.
Scenario B: you always use 20 grams of beans/grounds to brew your coffee. If you are using light roast coffee, you are actually putting FEWER beans or grounds (again, we are talking about the number of beans or grounds, not mass or volume) into that 20 grams than you would be if you were using dark roast coffee, because each light roast bean/ground is more dense than each dark roast bean/ground. You need fewer light roast beans/grounds to make up the same mass. Again, what the caffeine content really depends on is the number of beans/grounds - there is a fixed amount of caffeine in each bean which doesn’t change as you drive off moisture. So if you are measuring your dose by mass, light roast coffee actually gives you LESS caffeine in your cup than dark roast coffee.
To be clear, it isn’t the roast level itself that is affecting the amount of caffeine in the brew. It is the number of beans/grounds you are using, which will be different depending on how you are measuring your dose.
But what about espresso?
Espresso follows the same rules as any other brew method. The higher the dose, the more caffeine you get. If you use robusta, you will get about twice the caffeine that you would if you used arabica. Caffeine is a very fast-extracting compound, so even with the short extraction time, you are still extracting essentially all of the caffeine that is in the grounds. By the same logic, it makes no difference that cold brew is a many hour extraction. You get all the caffeine out very quickly. The espresso beverage of course has a higher concentration of caffeine than filter coffee does, but if you use an 18 gram dose to make espresso and an 18 gram dose to make a pourover, you’ll get pretty much the same amount of caffeine once you’ve drunk the whole beverage. There is a small difference in the amount of caffeine that gets extracted depending on your brew method, but not enough to get bogged down in those details. And you’ll find plenty of completely incorrect and contradictory information about those differences all over the internet! For example, even sources that might seem reputable (Food&Wine) get it wrong - they say that cold brew and French Press, due to coarser grounds being used (French Press grind size is a whole separate topic), have less caffeine than methods that use more finely ground coffee.
Questions? Shoot us an email at coffeeisafruit (at) vibrantcoffeeroasters (dot) com.
