4 Important Things that Affect Caffeine Content in Coffee

The curiosity about the caffeine content in coffee is widespread, and the answer you will find for this question after a quick search on the internet is that a cup of coffee has around 95mg of caffeine per cup (8 fl oz) (237 g). Although, if you see a precise answer like this, you shouldn't take it as the final truth.

In this article, I intend to help you understand four factors that can dictate the level of caffeine content in coffee and why these levels can vary quite a bit.

High levels of caffeine are normally associated with strong coffee, and we all agree some days, we wake up craving for the strongest coffee available in the world. But most of the time, we actually don’t know how to make it.

As a coffee roaster, I often get that question “what is your strongest coffee” or “which of your coffee blends is the strongest?”. But unfortunately, the answer to these common questions is not straight, and to be honest, there’s no absolute answer. 

The good news is, understanding these four important aspects that can affect the caffeine content in your cup will make you more confident to say if the coffee you are drinking is a strong coffee with a decent level of caffeine or not.

Here are the four things you need to understand:

1 – Coffee Bean Variety

Simplifying the coffee bean variety thing, I’ll be talking about two of them: Arabica and Robusta.

Nowadays, more and more coffee bag labels claiming 100% of Arabica beans in their coffee. Generally speaking, Arabica coffee tastes much better than Robusta, although when it comes to caffeine levels, Robusta coffee has around double the caffeine that Arabica has.

Coffee Arabica

Do you remember a delicious coffee you had recently? There’s a high chance of it being 100% Arabica coffee. Arabica is the most popular type of coffee everywhere you go.

Arabica is sweeter and less bitter than Robusta, which is related to its lower caffeine levels.

Arabica plant grows at higher altitude, require higher maintenance and are more susceptible to pests and diseases. It explains why Arabica coffee is more expensive than Robusta.

Coffee Robusta

The difference from Arabic coffee is not just on flavor. Robusta coffee is cheaper to produce because it can grow in lower altitudes, higher temperatures, and it’s way more resistant to bugs and diseases.

You won’t easily find a bag of coffee made of 100% of Robusta beans due to its burnt, rubbery, and bitter taste. However, Robusta is part of several espresso blends and also the majority of instant coffee.

Adding a certain percentage of Robusta in a coffee blend, the coffee company will reduce the shelf price of the coffee, achieving good-looking crema in the cup with a higher level of caffeine without compromise the taste so much.

As a general rule, Robusta has nearly twice as much caffeine as Arabica. On the other hand, Arabica has almost twice the concentration of sugar as Robusta. This explains a bit why Arabica tastes better than Robusta. In saying this, recently I had the chance to drink some good quality Robusta from India and Brazil, showing great potential for this variety.

2 – Coffee Roast Level (Light Roast or Dark Roast?)

I am not quite sure why most people associate a darker roast with a higher level of caffeine. I believe it happens regarding a more intense and bold taste found in darker blends of roasted coffee. The truth is that caffeine is extremely stable during the roasting process. Basically, there is no difference in loss of caffeine during the process.

Green coffee beans are very dense and contain water in their green form. During the roasting process, a bean loses its mass, becoming more and more brittle. Beans that are roasted longer are less dense (higher loss of water).

Darker beans are less dense. They lost more water during roasting. You end up having more beans by mass of dark roasts.

Lighter Roasts

  • Shorter roasting time
  • Less brittle, denser
  • Beans contain more water

Darker Roasts

  • Longer roasting time
  • More brittle, less dense
  • Beans contain less water

If you measure your coffee by volume, the lighter roast will have more beans and your coffee a little more caffeine.

If you use a scale and measure your coffee by weight, the darker roast will need few more beans to achieve the same weight as a lighter roasted bean. In this case, a coffee made with darker beans will contain a little more caffeine. 

3 – Coffee Brew Method

Different brewing methods extract different amounts of caffeine. It means if you’re using the same amount of coffee with different brewing methods, you will end up with a slightly different level of caffeine in your cup.

A longer brewing method normally extracts a bit more caffeine than a quick brew. But, of course, we can’t ignore the amount of coffee and the grind size. 

Just be careful when you brew your coffee for longer. If you use a fine grind size, your cup can get bitter-tasting. However, I strongly believe there’s no point in compromise taste to get a little extra caffeine.

In my opinion, there is no one best brewing method for caffeine extraction. Instead, every extraction method has its own characteristics. However, once you master each brewing method, you can apply few changes to extract a bit more caffeine into your cup.

4 – Coffee Grind Size

The ideal grind size when making coffee is the size that suits the chosen brewing method.

You can go from a super fine grind for Turkish coffee and then Espresso until a much coarser grind for a French Press and then Cold Brew. Just don’t forget these different grind sizes work well with their respective brewing method.

As a general rule, the finer the coffee grind size, the larger is the surface area for caffeine extraction. It’s also important to mention the hotter the water used to brew, the more extraction and thus more caffeine your coffee will have.

Things to consider

  • As more coffee you add to your recipe, the more caffeine you will get in your cup.
  • A combination of fine grind and long brew time will definitely optimize caffeine extraction.
  • Trying to increase the caffeine level in a cup tends to compromise the taste of your coffee.

What to do next

  • Check our brewing method article.
  • Play around with grind sizes, brewing time, and brewing methods to see if you can develop a more caffeinated but still delicious cup.
  • In my opinion, using the French Press is one of the easiest ways to play around with all the variables we’ve just seen in this article. You can try a different amount of coffee, water temperature, grind sizes, and brewing times.

The most important: Have fun! 

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