Caffeine content of different brewing methods

Question

For a given type of bean, do different brewing processes and temperatures (drip, French press, Mocha, espresso, cold brew, etc.) produce coffee with different caffeine content?

It would seem temperature isn't a factor because, according to this answer, "caffeine is chemically stable even when passed through its boiling point (evaporation temperature) of 312°C (593.6°F)".

The brewing method, however, would seem to matter. Mocha, espresso machines would seem to extract the most caffeine because they require finer grounds and use higher temperatures (steam) and pressure.

Answer 1

Short answer: No

Slightly longer answer: The temperature, pressure and method of brewing barely impact the amount of caffeine extracted from the bean.

Because caffeine dissolves so readily in hot water, the single most important factor in determining the amount of caffeine in the cup is the amount of coffee used to prepare said cup. Arabica beans contain about 0.8-1.4% of caffeine by weight, depending on the variety. So if you were to brew an espresso (15g in 30g out) or a pour over (15g in 250g out), you would have the same amount of caffeine in each beverage.

Answer 2

Espresso does indeed extract more caffeine than other brewing methods except possibly Turkish (which I'm not familiar with). There are a few reasons why.

Grind size is one: espresso's very fine grind size results in greater surface area of the beans compared to the grind sizes used for most other brewing methods.

Two is pressure. The pressure with which water is pushed through the coffee grinds agitates the grinds. As you probably have seen from stirring sugar or other solutes into water, agitating the solvent and/or the solute allows exposure of lower parts of the solvent to higher concentrations of the solute, resulting in faster / more complete dissolving.

Third is that concentration, which is related to the other two factors. Espresso uses a small amount of water to brew compared to drip, pour over, or French press. A double shot uses between 2 and 3 ounces of water to brew (some gets left behind in the portafilter), and the drink volume produces by this brew method (in the US) is only ~2 ounces. Caffeine per milliliter of espresso is nearly double that of the next highest contender (which is cold brew--which cold brew achieves by using a very long brew time).

That said, many coffee drinkers dilute their coffee with various additives. Diluting of course will change the consideration of caffeine concentration (but not caffeine content).

Answer 3

Although different brewing methods use different pressures, temperatures, brewing times, and grind sizes,

^{—The Craft and Science of Coffee p. 370}

these factors do not appreciately affect caffeine extraction efficiency, according to

• Alexia N. Gloess et al., “Comparison of Nine Common Coffee Extraction Methods: Instrumental and Sensory Analysis,” European Food Research and Technology 236, no. 4 (April 1, 2013): 607–27, DOI: 10.1007/s00217-013-1917-x, §9 Extraction Efficiency, p. 618:

the Bialetti moka pot (Bia) has the best "Caffeine per g R&G" extraction efficiency {plot (e) below}.

Caffeine content per gram of ground coffee (R&G) prepared according to the different extraction methods:

Key:

• Espresso from semi-automatic machine—(DE)
• Lungo from semi-automatic machine—(DL)
• Espresso from fully automatic machine—(SE)
• Lungo from fully automatic machine—(SL)
• Espresso—Nespresso (NE)
• Espresso—Bialetti (Bia)
• Lungo—French Press (Bo)
• Lungo—Karlsbader Kanne (KK)
• Lungo—Filter Coffee (F)