Which coffee brewing method has the most caffeine: drip brew? French press? Espresso?

Many believe the answer is espresso. After all, espresso is concentrated coffee, brewed by the pressure of hot water flowing through finely-ground coffee beans. With espresso being a small, concentrated amount of coffee, it would make sense that espresso has the most caffeine. But, drip brew coffee has hot water continuously passing through coffee grounds, potentially extracting more and more of the caffeine out of the bean, so drip brew has to have more caffeine than espresso. Then again, with a french press, coffee grounds are soaked with hot water for a full infusion, steeping with full on contact for 4 minutes, so french press brewing has to extract more caffeine than both espresso and drip brew… right?

Back in ’79, Bunker and McWilliams published a paper after studying the caffeine content of common beverages. Here are their coffee-based findings (caffeine content noted in mg):
* espresso: 1 cup (1.5–2 oz, 45–60 ml) = 100 mg
* brewed: 1 cup (7 oz, 207 ml) = 80–135 mg (107.5 mg average)
* drip: 1 cup (7 oz, 207 ml) = 115–175 mg (145 mg average)

Case closed. Drip brew has the highest caffeine content and espresso the lowest. Well, in reality, it’s not that straight forward and is a little difficult to answer which brewing method has more caffeine because, I believe the answer depends on a lot of different factors…

Variety of Bean (robusta vs. arabica)
Robusta coffee beans have twice the caffeine content than arabica beans. Although arabica beans are considered to be of higher quality, robusta beans are used in many dark roast espresso blends… so, naturally, this will cause a higher caffeine content in espresso or any kind of blended (non-single origin) coffees that use robusta.

Roast level (light roast vs. dark roast)
Surprisingly, roast level impacts caffeine content. Dark roasted coffee is often associated with being “bold” and having a lot of caffeine, but that’s simply not true. The longer a coffee bean is roasted, the more the caffeine is burned off during the roast – so lighter roasts have a higher caffeine content than darker roasts. Since dark roasted coffee is generally used for making espresso, this impacts (lowers) the caffeine content.

Temperature of Water
Brew temperature is an important factor. Proper coffee extraction happens between 195-205 degrees, but most drip brewers only get up to about 190 degrees. Espresso machines usually do a good job brewing at near boiling temps. With french press coffee, you have total control over the temperature. If you want to pour boiling water (212 degrees) over your grounds, you can (but we don’t recommend it!). The point is, water temp. can vary by brewing method, and the hotter the water is, the better the extraction (to a point, please don’t exceed 205 degrees). With better extraction comes better tasting coffee, but also better caffeine extraction, too.

Amount of Ground Coffee Used
This one seems rather obvious, but I admit I didn’t really think about it until I wrote this post. The more coffee grounds you use, no matter your brewing method, the higher the caffeine content. Duh. But, it’s important to list as a variable, since some use more ground coffee than others when brewing based on taste preference.

Length of Brew Time
Another factor is the length of brew time. Generally speaking, drip brew coffee does have more caffeine than espresso. Why? Because with drip brew, hot water is continuously dripping through a bed of coffee grounds for 3 minutes. A shot of espresso is pulled in 20-30 seconds. Compared to drip brew, where coffee is in contact with hot water 6 times longer than the hot water that is in contact with coffee grounds during an espresso extraction, you can see how drip would have more caffeine. Not to mention with french press, and a recommended steep time of 4 minutes, more caffeine could potentially be extracted. It’s easy to see that, in terms of length of brew, drip brew coffee makes contact with hot water much longer than espresso does. But, if french press coffee steeps for 4 minutes, usually a minute longer than drip brew, how come french press coffee doesn’t have the highest caffeine content? The answer is the coarseness of the coffee grounds, which we speak to next.

Grind Level
The size of the grind makes a difference. For french press coffee, we use a coarse grind. For drip, a medium grind. Espresso, a fine grind. If you have a conical burr grinder, you may notice that you have to “dial in” the right grind to get your coffee to taste better. Maybe it’s too coarse, so you adjust the setting. Or it’s too bitter, so you adjust the setting to make it coarser. The finer you grind your coffee, the shorter the amount of time it will take to brew/extract, and if you leave all other variables the same (amount of coffee used, amount of hot water, brew length, etc.), a finer grind can mean more caffeine extraction.

Beverage Size
Sure, drip brew coffee generally has a higher caffeine content than espresso. But is that really comparing apples to apples? I mean, for drip brew, you could be using an 8 or 12 oz mug. Meanwhile, a shot of espresso could be 1.5 oz. Should we really be comparing the two the way we do? If we look at caffeine content per ounce, espresso would win. Just a thought.

What are your thoughts on coffee and caffeine? Are there any other variables you can think of that might influence caffeine content in these brewing methods? Let me know in the comments. -Ken

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Time Your Coffee Grind

Timing is everything… and the timing of when you grind your coffee beans matters. I’ve briefly mentioned it before, but there is a huge difference in the taste of brewed coffee when you brew within 60 seconds of grinding vs. brewing coffee with beans you ground the night before while setting up the coffee machine before bed (or worse, preground coffee). Here’s why…

The thing that makes coffee taste so good are the coffee oils found inside the coffee beans. During the coffee roasting process, sugars are caramelized and oils are formed and trapped inside the bean, encapsulated and protected from the outside world for a very short period of time. These coffee oils are essentially what gives brewed coffee its great taste.

In a perfect world, these oils would just hang out inside the bean indefinitely, but there are 2 forces working against these oils: carbon dioxide and oxygen. These two goons have a special assignment: destroy the coffee oils within 10 days, and if we let them, they’ll do just that – every time.

Let’s take carbon dioxide. One result of the coffee roasting process is that carbon dioxide is emitted from a freshly roasted coffee bean for about 2 weeks. The CO2 is the result of the volatile roasting process… think of it like a Pepsi can shaken up. It takes a little while for the Pepsi to normalize and the pressure to subside. Same thing with fresh roasted coffee – the coffee bean is in a volatile state and over the course of 10 days or so, the carbon dioxide slowly pushes the trapped coffee oils hiding inside the bean out to the surface, the oils escaping through cracks and crevices found throughout the interior and surface of the bean. The cracks are too small for oxygen to enter, so the carbon dioxide does the dirty work by forcing the oils out.

Now that the coffee oils are exposed on the surface of the bean, the second force – oxygen – takes over by attacking the oils and in a very small amount of time (30-60 minutes) the oils become rancid and if the beans are used, the resulting coffee will taste very stale and bitter.

With that background, it’s easy to see how ground coffee creates so much more surface area for oxygen to come in and do its thing. And not only do you have 30-60 minutes to brew your coffee after grinding, but 80% of any carbon dioxide left inside the coffee beans dissipate into the atmosphere within 60 seconds of grinding! CO2 is the main transport mechanism for pushing out any oils inside the bean casing into the water when we brew, so we really need to do what we can (brew quickly after grinding!) to use it to our advantage to get those oils out.

Try brewing within 60 seconds of grinding your coffee beans and I bet you’ll make a better tasting cup of coffee. -Ken

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