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Friday
Aug192011

Coffee and Caffeine. Which Brewing Method Has the Most?

Is it espresso, a small, concentrated amount of coffee, brewed by hot water flowing through finely ground coffee?  Or drip, with the hot water passing continuously through the coffee grounds, potentially extracting more caffeine from the bean?   Could it be french press with the coffee grounds soaked in hot water for a full infusion, steeping for 4 minutes?

  • A typical cup of drip coffee (8oz) contains approximately 60-100 mg of caffeine.  60 - 100 mg of caffeine?  Why such the variation in the amount of caffeine?  There are several factors including brew time, dwell time, water temperature, grind level, roast level, bean type, blend, etc. that all have a significant affect on the final extraction of caffeine; 
  • Looking  at the data,  its  clear that a cup of drip coffee contains much MORE caffeine than a shot of espresso (30-50mg).   However, if you consider the amount of caffeine per ounce, espresso has more than drip coffee;  
  • Due to the brewing process, and dependent upon the the length of time it is brewed (the longer it steeps, the higher the caffeine content)  and the coffee to water ratio, French Press coffee has one of the highest caffeine contents (80-100 mg); 
  • Instant coffee has the least amount of caffeine of coffee with approximately 50-60 mg of caffeine per heaped teaspoon); and 
  • Yes, decaffeinated Coffee contains a small amount of caffeine - only about 2-4 mg per cup.

As mentioned above there are several factors, in addition to brewing process, that affects the amount of caffeine: Variety of coffee bean, roast level, temperature of water, amount of coffee, brew time, grind level and, of course, beverage size.   

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.   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)

Roast level impacts caffeine content. Dark roasted coffee is often associated with being “bold” and having a lot of caffeine, which is not the case. The longer a coffee bean is roasted, the more the caffeine is burned off during the roast, leaving lighter roasts with 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, however 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 with the option of pouring boiling water (212 degrees) over your grounds (but we don’t recommend it!). Water temp. can vary by brewing method - the hotter the water, the better the extraction (to a point, please don’t exceed 205 degrees). With better extraction comes better tasting coffee and caffeine extraction.

Amount of Ground Coffee Used

The more coffee grounds you use, no matter your brewing method, the higher the caffeine content. Although obvious, it is important to list 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? 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. 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. 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.  Read on...

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 “coffee bean to coffee bean”? For drip brew, you are most likely  using an 8 or 12 oz mug. Meanwhile, a shot of espresso could be 1.5 oz. As mentioned earlier, when we look at caffeine content per ounce, espresso would win.

With so many factors, the most important is personal taste...the type of brew method you choose to use.  

Reader Comments (2)

All you say is both/either factually correct or having properties that are on-the-mark. Given that, and acknowledging that your answer must be an approximation, here is my rather precise QUESTION:

What is the approximate TOTAL CAFFEINE CONTENT in a cup containing three shots of espresso made with all factors [i.e., water temperature] set to maximize caffeine extraction. The total water volume at the end of preparation being irrelevant because hot water is added - which does not change the total caffeine content. The coffee is a light roast [Costa Rican] Arabica.

Thank you for your answer, even though it is estimated,

Emeritus

July 8, 2014 | Unregistered CommenterEmeritus

thank you. perhaps, for me using a SAECO espresso machine and arabica beans, the most important single item is to use light roast.

can you give me a simple approximation: with that machine or other set on highest temp, not-quite-finest grind, and longest brew time [just approximate] WHAT IS THE TOTAL CAFFEINE CONTENT PER SHOT?

[by approximate, i mean an answer like "200 mg per shot" rather than trying to be more accurate or precise by answering "247.3 mg per shot". Even if you have an answer such as 32.5 mg per shot just use the approximation of 30. again, thank you]

July 15, 2014 | Unregistered CommenterEmeritus

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